Celebrating 20 years of Swift Discoveries

24 Mar 2025, 14:00 → 28 Mar 2025, 17:00 Europe/Rome

Florence, Italy

When the Neil Gehrels Swift Observatory was launched on November 20, 2004, its prime objective was to chase Gamma-Ray Bursts. Since then, the mission has far exceeded its original scientific goals. Swift discovered the first afterglows and host galaxies of short-hard GRBs, and a growing sample of events from the local Universe to the epoch of reionization, providing arcsecond positions, light curves, and spectra for more than 1,500 events.

Over time, Swift has become an unequalled Target of Opportunity machine for the astronomical community, thanks to a unique combination of sensitive instrumentation and operational flexibility that provides unprecedented observational capabilities: rapid response coupled with multi-wavelength monitoring of any class of transient/variable object.

After almost 20 years of operations, we think it a fitting occasion to revisit Swift’s achievements and to put our mission in the context of the rapidly evolving fields of time-domain and multi-messenger astrophysics. Therefore, we are organizing the meeting "Celebrating 20 years of Swift Discoveries", to be held on March 24-28, 2025, in Florence, Italy, at the Firenze Fiera conference center.

 

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IMPORTANT DATES

 

2024 Oct 29: opening of registration & abstract submission

2025 Jan  7: deadline for abstract submission

2025 Feb 10: deadline for early registration

2025 Mar 16: deadline for registration

 

2025 Mar 24 - 28: conference

 

The scientific program will be available by early February. 

 

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Design by Laura Barbalini

A3 - locandina Swift20.png

Monday 24 March

16:30 → 18:00 Registration

18:00 → 19:30 Welcome cocktail

19:00 → 20:30 Opening talks

19:00 Historical Talk on Swift - Nick White

19:30 Remembering Neil Gehrels and Guido Chincarini - Brad Cenko, Filippo Zerbi

Tuesday 25 March

08:30 → 09:00 Registration

09:00 → 09:15 Welcome

Presentazione_LOC.pdf

welcome1.pptx

Z_2025_Swift20_song.pdf

09:15 → 10:30 GRB progenitors (long & short)

09:15 Gamma-ray burst progenitors revisited

In the past few years, observations spearheaded and enabled by Swift have seen a re-writing of the story of gamma-ray burst (GRB) progenitors. It is now apparent that the observational dichotomy between long- and short-GRBs does not map cleanly to two distinct progenitor channels -- massive stars and merging compact objects. Instead, growing evidence suggests that a small minority of short-GRBs can arise from massive stars, and a potentially significant number of long-GRBs may arise from mergers. At the same time, new capabilities for finding GRB-like objects outside of the gamma-ray regime in wide-field X-ray or even optical surveys offer the possibility of further stretching the physical systems creating relativistic, GRB-like outflows. I will provide an overview of the observational evidence that has been built for this new, more diverse view of the transient high-energy sky and consider how this landscape may become richer still in the coming years.

Speaker: Andrew Levan (Radboud University)

grb_progenitors_revisited.pptx

09:45 Exploring pathways for long-duration gamma-ray bursts from compact object mergers

In the decades following the discovery of gamma-ray bursts (GRBs) in the 1960s, an understanding emerged that there are two classes of progenitor. The short duration (<2s) bursts arise from binary neutron star mergers (confirmed by the coincident LIGO/VIRGO gravitational wave detection of GRB170817A), and the long bursts (>2s) arise from the core-collapse of massive stars. However, the recent GRBs 211211A and 230307A spectacularly defied this convention. These bursts were unambiguously long, but far away from star-formation and without supernovae. They instead showed kilonovae - explosions powered by the radioactive decay of newly produced r-process elements in an extremely neutron-rich environment, and the tell-tale sign of a compact binary merger. White dwarf - neutron star/black hole mergers have been suggested as possible channel for these long-duration merger GRBs. In this work, we combine modelling of the host galaxies of GRBs 211211A and 230307A with binary population synthesis predictions to test whether the observed locations of these GRBs are consistent with a merger involving a white dwarf, and compare predictions for the cosmological rates of binary compact object mergers with the rates of short and long GRBs.

Speaker: Dr Ashley Chrimes (ESA/ESTEC)

Swift20_aac_v3.pdf

10:00 The puzzling long GRB 191019A: Evidence for Kilonova Light

GRB 191019A was a long Gamma-ray burst (GRB) that triggered Swift/BAT and lasted about 65 s and, as such, originally thought to have a core-collapse origin. However, no associated supernova was detected following the optical afterglow despite deep follow-up, which suggested that the burst was caused by the merger of two compact stellar objects. This is also supported by the published properties of its host-galaxy (z=0.248), which is a massive and passive galaxy, unusual for a collapsar event.
We thus re-analyzed unpublished GROND multi-band (g'r'i'z'JHKs) data obtained between 0.4 and 15 days post trigger and obtained additional late-time LBT imaging. Image subtraction confirmed the optical counterpart in all four optical bands and suggested the presence of a rebrightening around 1-2 days, with magnitude and peak timescale compatible with an AT2017gfo-like KN at the same redshift.
Incorporating publicly available Swift-XRT data, a joint fit of an afterglow plus a kilonova model revealed a better match than an afterglow-only scenario. Our findings strongly suggest that GRB 191019A belongs to the increasing list of binary-merger long GRBs like GRB 211211A and GRB 230307A.

Speaker: Andrea Rossi (Istituto Nazionale di Astrofisica (INAF))

rossi_andrea.pdf

10:15 Exploring Short Gamma-Ray Bursts: afterglow insights from the S-BAT4 extended sample

In the context of Gamma-Ray Bursts (GRBs) astrophysics, the class of short GRBs is particularly fascinating since they are expected to be produced in compact binary mergers, and to be associated with gravitational wave (GW) events. Double neutron star or neutron star-black hole binaries likely generate another electromagnetic transient, known as Kilonova (KN). As such, with the present and future planned GW observing runs we expect to observe more events with coincident detections in addition to GW170817/GRB170817A/AT2017gfo, the only observation of a short GRB, a GW, and a KN obtained so far. The knowledge of the population of short GRBs is thus essential for proper analysis and characterization of these events and a deeper understanding of the underlying physics.
In the talk, I will present a carefully selected sample of short gamma-ray bursts (SGRBs) observed with the Neil Gehrels Swift Observatory from Nov. 2004 to Dec. 2022, namely the S-BAT4 extended sample. GRBs selection criteria include bright events, prompt satellite repointing, and favorable observing conditions for the redshift determination from the ground. The sample consists of 51 events, 62% of which have a spectroscopic redshift measure, and for other 17% a photometric \textit{z} has been determined. Such flux-limited sample minimizes any redshift-related selection effects and can provide a robust base for the study of the energetics, redshift distribution, and environment of the Swift bright population of SGRBs. The prompt and afterglow emissions have been analyzed by computing the rest frame properties of the bursts in terms of energetics and luminosity. In particular, the analysis of the afterglow properties of the sample allowed us to derive and classify 35 and 12 rest-frame light curves in the X-rays and in the optical-near infrared bands, respectively. The majority of the light curves reveal a different evolution in the X-rays and in the optical band, at least at early times. In addition, the comparison of afterglow luminosity at different rest-frame times with prompt emission features suggests a different origin for the X-ray and optical emission, at least during the early phases, with the presence of additional components (e.g. late time activity of the central engine) on top of the pure afterglow emission, which dominates at later times. The large statistics of the sample also gives the opportunity to study the intrinsic absorption properties of short GRBs. Their distribution has been found to be consistent with 0, with no events displaying significant local absorption.
The comparison with a sample of long GRBs (the BAT6 sample) built with similar criteria and of comparable size revealed the different nature of the events belonging to the two samples, and this will be a useful benchmark for a more detailed classification of GRBs that will be observed in the future.

Speaker: Riccardo Brivio (Istituto Nazionale di Astrofisica (INAF))

Brivio_SBAT4ext_Swift20.pdf

10:30 → 11:00 Coffee break

11:00 → 12:30 GRB central engines and jets

11:00 Central Engines of Gamma-ray Bursts and Heavy Element Nucleosynthesis

I will overview central engine models for gamma-ray burst jets and their connection to the creation of heavy element nucleosynthesis. Particular emphasis will be placed on the recent discovery of long GRBs with kilonova emission and how this discovery constrains the origin of jets from neutron star mergers. Time permitting, I will address possible connections between GRBs and other engine-powered transients such as superluminous supernovae and FBOTs.

Speaker: Prof. Brian Metzger (Columbia University/Flatiron Institute)

11:30 Measuring the expansion of GRB afterglows

Radio observations employing the very long baseline interferometry (VLBI) technique offer a crucial insight into the structure and dynamics of Gamma-Ray Burst (GRB) jets. Specifically, VLBI serves as a fundamental tool for measuring the apparent superluminal expansion (in on-axis GRBs) and proper motion (in off-axis GRBs) of the GRB blast wave. These measurements enable constraints on the outflow geometry and characterisation of the circum-burst medium, complementary to light curve and spectral modelling. This presentation will highlight the significant contribution of VLBI to GRB science, with a particular focus on recent results concerning GRB221009A, the brightest GRB recorded to date. For the latter, the observed size evolution probed by VLBI measurements suggests that the reverse shock and the forward shock dominate the afterglow emission at different frequencies and times. Lastly, future prospects for GRB research through radio interferometry will be discussed.

Speaker: Stefano Giarratana (Istituto Nazionale di Astrofisica (INAF))

11:45 The BOAT that rocked: the radio afterglow of GRB 221009A

GRB 221009A has been dubbed the BOAT or brightest of all time for its recording-breaking gamma-ray brightness. At radio frequencies, it also holds the record as the brightest counterpart detected to date. In this talk, I will present a summary of the observations conducted by my collaborators and I (Bright & Rhodes et al 2023, Rhodes et al 2024), resulting in the most comprehensive radio coverage of any GRB to date, spanning over three orders of magnitude in frequency space. Our studies have resulted in numerous interesting discoveries including a long-lived synchrotron self-absorbed reverse shock as well as a flat spectrum extending up to sub-mm frequencies which cannot be explained within the ‘standard’ afterglow picture. I will discuss the importances of such coverage for our understanding of jet geometry and theoretical modelling. Finally, I hope to present a brief overview of our plans to continue monitoring this fascinating object.

Speaker: Lauren Rhodes (McGill)

12:00 Where Are All of the Off-Axis GRBs? A Late-Time Radio Campaign of Ic Broad Line Supernovae

Since the launch of Swift, it has detected more than 1500 GRBs, ~90% of which are long duration GRBs. Almost every spectroscopically confirmed SN associated with a long GRB has been hydrogen and helium poor with broad lines (Ic-BL), indicating a stripped massive star progenitor with fast winds that produced a highly-collimated jet viewed on-axis. A critical prediction of this progenitor model is that there should be a large number of off-axis jets accompanied by Ic-BL SNe - but this has yet to be observationally confirmed. Years after the explosion, the off-axis jet will have decelerated and become spherical, resulting in a late-rising radio light curve. Here, I will present late time radio observations of a sample of Ic-BL SNe that have been shown to have exploded in the same host environments as long GRBs, making them some of the strongest candidates for off-axis GRBs to-date. I will use these observations to place constraints on the existence of off-axis jets within this sample and within the local universe, which will help us better understand the nature of the long GRBs detected by Swift.

Speaker: Dr Genevieve Schroeder (Cornell University)

Swift20_GenevieveSchroeder.key

12:15 Soft X-ray prompt emission from a high-redshift gamma-ray burst EP240315a

Long gamma-ray bursts (GRBs) are believed to originate from core collapse of massive stars. High-redshift GRBs can probe the star formation and reionization history of the early universe, but their detection remains rare. Here we report the detection of a GRB triggered in the 0.5–4 keV band by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated as EP240315a, whose bright peak was also detected by the Swift Burst Alert Telescope and Konus-Wind through off-line analyses. At a redshift of $z=4.859$, EP240315a showed a much longer and more complicated light curve in the soft X-ray band than in gamma-rays. Benefiting from a large field-of-view ($\sim$3600 deg$^2$) and a high sensitivity, EP-WXT captured the earlier engine activation and extended late engine activity through a continuous detection. With a peak X-ray flux at the faint end of previously known high-$z$ GRBs, the detection of EP240315a demonstrates the great potential for EP to study the early universe via GRBs.

Speaker: Yuan Liu (National Astronomical Observatories, Chinese Academy of Sciences)

EP240315a_liuyuan.pptx

12:30 → 14:00 Lunch

14:00 → 14:30 Poster Session: Poster view

14:02 Extended Mapping the Universe with Gamma-Ray Bursts

Recently we searched for large scale structures in the Universe using 542 GRBs with known redshifts. In our published paper we checked for over densities on different scales. In our new work, we extend our search to larger scales. We found several deviations, among them a group of four GRBs and an extended volume of the so called Hercules–Corona Borealis Great Wall (HCBGW). The estimated 2 Gpc size of the HCBGW is almost an order of magnitude larger than the 300 Mpc size that would be accepted if the cosmological principle (CP) is valid. Consequently, if the HCBGW is a gravitationally bound object, its existence violates the CP. However, if the HCBGW is a large-scale time/space fluctuation of the GRB birth rate, then its existence does not necessarily contradict CP.

Speaker: Istvan Horvath (University of Public Service, Budapest, Hungary)

HorvathExploringtheUniversethroughGammaRayBurstMapping.pdf

14:04 A new adaptive density estimator for 1-D point processes: the (not so) fine details of the GRBs' redshift distribution

We have developed a density estimator for 1-D point processes. It is based on the continuous smooth function approximation, while information in the global density distribution is also applied. Using MC simulations we have determined the optimal parameters for low count distributions like the GRBs' redshift data. The results detailing the GRBs' redshift distribution also discussed briefly.

Speaker: Istvan Horvath (University of Public Service, Budapest, Hungary)

HorvathBagoly.pdf

14:06 Blue Source on a BOAT: Late-time (t > 185 d) HST and JWST analysis of GRB 221009A

GRB 221009A is the brightest gamma-ray burst ever detected by the Swift Observatory, with the highest peak gamma-ray flux for a GRB. It was detected once by the Burst Alert Telescope (BAT) during the prompt emission and again during the high-energy afterglow phase–a feat matched by no other GRB. Early data (t < 60 d) has shown a complicated picture with several projects finding a wide range of flux limits for the associated supernova (10–70% x SN 1998bw), theory-defying synchrotron physics for the afterglow, and breaks in the optical light curves and decay slopes leading to possible jet break times of 45 min to > 100 days after trigger. In this talk, I present late-time Hubble Space Telescope (HST)/WFC3 and JWST/NIRCam imaging of the afterglow and host galaxy of GRB 221009A at t ~ 185, 277, and 345 days post-trigger. The joint archival ground, HST, and JWST light curve fits show strong support for a break in the light curve decay slope at t = 50 +/- 10 days (observer-frame) and a supernova at 1.4+0.37−0.40× the optical/NIR flux of SN 1998bw. This break is consistent with an interpretation as a jet break when requiring slow-cooling electrons in a wind medium with the electron energy spectral index, p > 2, and ν_m < ν_c. The light curve and joint HST/JWST spectral energy distribution (SED) also show evidence for the late-time emergence of a bluer component in addition to the fading afterglow and supernova. We find consistency with the interpretations that this source is either a young, massive, low-metallicity star cluster or a scattered light echo of the afterglow.

Speaker: Huei Sears (Rutgers, The State University of New Jersey)

Sears Swift 20 years Poster A0.pdf

14:07 Celebrating two decades of SWIFT and H.E.S.S.: A joint history of Gamma-Ray Bursts follow-up

Gamma-Ray Bursts (GRBs) are among the most energetic phenomena in the universe, acting as excellent astrophysical laboratories in which to study extreme processes. For the last twenty years, not only has the SWIFT telescope immensely contributed to the field of GRB detection but it has also allowed for follow-up observations thanks to its rapid and precise localization. During this period, the H.E.S.S. (High Energy Stereoscopic System) observatory has played a crucial role in the search for and detection of Very High-Energy (VHE) gamma-ray counterparts from SWIFT public alerts.

This presentation will give an overview of the H.E.S.S. GRB follow-up program, describing the strategy we use to maximize the opportunity of detecting a VHE counterpart from a trigger alert distributed by space-based telescopes. To illustrate the latter, we will present a recent GRB ToO observation detailing the observation strategy and including every step followed, from the reception of the alert up to the end of the survey. Key results of the subsequent analysis, like significance, excess maps, and differential upper limits, will be presented as the final scientific outcome. Furthermore, celebrating the joint effort for a multi-wavelength picture of GRBs, we will present a statistical study of the H.E.S.S. follow-up observations of SWIFT-detected GRBs over the past two decades. Elements like observation and detection rates, relevant results, as well as possible opportunities for future follow-ups and analysis, will take part in this summary.

The presentation will highlight the importance of the coordination between space-based telescopes and ground-based observatories by showing how SWIFT public alerts and their quick follow-up by H.E.S.S. have significantly improved the scientific return of the field.

Speaker: Bernardo Cornejo (CEA / IRFU - DPhP)

Cornejo_Bernardo.pdf

14:08 The UVOT Image Subtraction Pipeline

The detection of faint optical transients is a critical component of gravitational wave (GW) follow-up efforts. Compact object mergers (e.g., binary neutron stars) produce kilonovae -- thermal transients powered by the radioactive decay of r-process elements. Unlike GRB jets, kilonovae are comparatively isotropic and thus may offer a higher likelihood of detection. However, their faintness and location within host galaxies make their detection challenging, as galactic diffuse emission can obscure the transient signal. To address this, we present a new pipeline for automated image subtraction of UVOT GW follow-up data. By utilizing high-quality template images, the pipeline effectively removes the galactic background, enabling the detection of faint transients embedded within host galaxies. We will describe the methodology and demonstrate the pipeline’s performance on simulated and real UVOT observations, and discuss its potential in finding electromagnetic counterparts to GW events, as well as other ultraviolet transients such as supernova shock breakouts, tidal disruption events, and stellar flares.

Speaker: Noel Klingler (NASA-GSFC / UMBC / CRESST II)

UVOT_image_subtraction_pipeline.pdf

14:09 Simultaneous Swift and TNO Monitoring of the Ultraluminous X-ray Source Holmberg IX X-1

Ultraluminous X-ray sources (ULXs) are extragalactic, non-nuclear X-ray point sources with luminosities exceeding the Eddington limit for a 10 solar-mass black hole. These sources are widely believed to be X-ray binaries containing black holes or neutron stars that accrete matter at super-Eddington rates. However, the exact mechanisms and geometry of this accretion process remain poorly understood. Holmberg IX X-1 is a nearby ULX that has been extensively observed in the X-ray waveband by several observatories, including Swift, due to its relatively high flux and proximity. Despite this, optical observations of the source remain limited. In this study, we performed semi-simultaneous X-ray and optical observations of Holmberg IX X-1 using the Swift X-ray Observatory and the Thai National Observatory (TNO). Observations were conducted over three consecutive nights, with about 1-2 hour observation window each night, to monitor the source and investigate its variability across both wavebands. In this presentation, we will report on the variability observed in the X-ray and optical wavebands, assess potential correlations between the datasets, and examine evidence for periodic modulation. The implications of these findings will be discussed.

Speaker: Dr Wasutep Luangtip (Srinakharinwirot University)

Poster_Swift.pdf

14:10 Rapid accretion state changes in super-massive black holes

The dynamic environment which exists in black hole accretion discs has traditionally been probed in stellar-mass Galactic black holes where the timescale for changes is short. In principle, if the quantity of material in a disc around a super-massive black hole is small and is not replenished, then the disc will drain on a timescale of a few hundred days and the system can pass through several states during a short monitoring campaign. Partial tidal disruption events, where the atmosphere of a star is stripped and consumed by a nuclear black hole, gives us the perfect opportunity to test whether disc states and state changes are mass-invariant? We present some recent results.

Speaker: Mr Richard Saxton (XMM SOC, ESAC)

Saxton_Richard_1.pdf

14:11 Identifying potential Binary Neutron Star merger events from the Fermi GBM Gamma-Ray Burst Catalog

The detection of GRB 170817A, coincident with the gravitational wave signal GW170817 from a binary neutron star (BNS) merger, confirmed the link between short gamma-ray bursts (sGRBs) and compact object mergers. I will present a study focused on the identification of potential sGRBs associated with BNS mergers by analyzing the Fermi GBM Burst Catalog using an unsupervised machine learning approach.
The results reveal a distinct cluster of merger-like GRB events, including GRB 170817A and GRB 150101B, and other kilonova-associated events. Validation of the method was performed using multiple dimensionality reduction techniques—PCA, t-SNE, and UMAP—along with comparisons to kilonova candidates from other studies, confirming the robustness of the approach. Furthermore a pipeline has been developed to identify host galaxies for potentially nearby off-axis GRB events. In this way we can optimize the identification and follow-up observations for kilonovae detected through their associated off-axis sGRBs.

Speaker: Ines Francesca Giudice (Istituto Nazionale di Astrofisica (INAF))

poster_template-7.pdf

14:15 10-yrs follow-up of the ANTARES neutrino alerts by Swift

High-energy neutrinos could be produced in the interaction of charged cosmic rays with matter or radiation surrounding astrophysical sources. To look for transient sources associated with neutrino emission, a follow-up program of neutrino alerts has been operating within the ANTARES Collaboration since 2009. For the highest energy neutrinos. this program has triggered the Neil Gehrels Swift Observatory immediately after the detection of any relevant neutrino candidate. The results of twelve years of observations are reported. In September 2015, ANTARES issued a neutrino alert and during the follow-up, a potential transient counterpart was identified by Swift/XRT. A multi-wavelength follow-up campaign has allowed to identify the nature of this source and has proven its fortuitous association with the neutrino. No other X-ray counterpart has been significantly associated with an ANTARES candidate neutrino signal. Constraints on transient neutrino emission have been set. The return of experience is particularly important for the alert system of KM3NeT, the next generation neutrino telescope in the Mediterranean Sea, which should start beginning of 2025.

Speaker: Damien Dornic (CPPM/CNRS)

poster_Dornic_Swift_March2025.pdf

14:16 Old novae in the eROSITA All Sky Survey

Nova explosions are thermonuclear events on top of an accreting white dwarf. The nova event results in the increase of the optical luminosity by 7-8 orders of magnitude that makes the nova outburst detectable at any distance in the Galaxy. However, due to the resulting distance distribution of novae in the Galaxy, the host system remains unknown for most cases. Accretion powers X-rays in the host system once the mass transfer is resumed and the white dwarf starts to accrete again as a cataclysmic variable. We have searched for old novae in the German data of the eROSITA X-ray All Sky Survey and have identified 16 new cataclysmic variables that have been hosted novae explosions. We can probe for the first time the evolution of the accretion rate during the first decades after the outburst and identify new Intermedate Polar candidates among old novae, increasing the fraction of known novae outbursts occurring in magnetic systems.

Speaker: Gloria Sala (Universitat Politecnica de Catalunya)

Old_novae_in_eRASS_Sala.pdf

14:17 A library of super Eddington outbursts in the era of modern observatories

X-ray pulsars offer a unique laboratory for the study of radiation processes in extreme accretion are X-ray pulsars. These are found typically in high-mass X-ray binaries (HMXBs), while the brightest and most variable ones are those where the donor is a Be star (i.e. BeXRBs). Their environment combines some of the strongest magnetic fields (> 10^12 G) and effects of strong gravity, while also allowing us to gain insight onto the Neutron Stars (NS) equation of state. Bright outbursts of BeXRBs have also helped us understand the brightest binary systems, the so-called Ultra-luminous X-ray sources.

We analyzed X-ray data from multiple observatories (e.g. Swift, NICER, NuSTAR, XMM-Newton) from super-Eddington outbursts of BeXRB pulsars in the local Universe (LMC, SMC or Milky Way). We studied their spectral hardness and pulsed fraction evolution with X-ray Luminosity. We identified patterns of variability that hint at changes in the accretion regime and probed super Eddington accretion. Here we present results from this unique library of events.

Speaker: Georgios Vasilopoulos (National and Kapodistrian University of Athens)

14:18 Constraints on FRB emission in the aftermath of GRBs

The physical origin of Fast Radio Bursts (FRBs) is still unknown. Many models consider magnetars as possible FRB sources, supported by the observational association of FRBs with the galactic magnetar SGR 1935+2154. Magnetars are also thought to be the source of the power of a fraction of Gamma Ray Bursts (GRBs), opening the possibility that the two extreme phenomena have a common progenitor.
In this work we present a new, systematic search for GRB-FRB association, using the most updated catalog of FRBs observed with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) instrument, and the sample of all GRBs detected by Swift so far. We also show, using a synthetic population of FRBs associated to Swift GRBs, how likely it is to have a joint detection with current and future radio facilities.
With our analysis we only recovered two, low significant, possible GRB-FRB associations already reported in literature; however the absence of any unambiguous association so far between Swift GRBs and FRBs cannot exclude that the two populations are connected, given the characteristics of current GRB and FRB detectors. In the next decade, with new generations of GRB and FRB detectors there will be a higher probability to detect joint GRB-FRB events, if any.

Speaker: Matteo Ferro (Istituto Nazionale di Astrofisica (INAF))

poster.pdf

14:19 Distinguishing between real transients and ghost sources in Swift/UVOT observations

In recent years Swift/UVOT has taken on a key role in identifying and following up transients. While automated source detection and difference imaging can help in finding transients, these tools cannot distinguish between real transients and star-like image artefacts caused by stray light. Image artefacts such as readout streaks or various ring structures are easy to identify by eye, and we have programs to identify these and flag sources within them. However, during the gravitational wave EM followup searches begun in 2016, we started to identify a small number of star-like features, "ghosts" of bright sources lying within a certain radius of the centre of the field of view. In this poster we will show how we identify these ghosts and how we intend to use the calibration to prevent the follow up of falsely identified new sources.

Speaker: Dr Alice Breeveld (UCL-MSSL)

GhostsPoster.pdf

14:20 In-flight spectral cross-calibration of ECLAIRs and GRM on board SVOM

The two high-energy instruments onboard the SVOM satellite, ECLAIRs and GRM, are expected to bring significant contributions in answering fundamental questions on Gamma-Ray Bursts (GRBs) and other high-energy transients. In particular, their joint analysis represents a clear asset compared to other missions for GRB prompt emission spectroscopy (Bernardini et al. 2017). This leads to stringent requirements in terms of inter-calibration between these two instruments. While for a coded mask instrument like ECLAIRs the reconstruction of the flux of bright steady sources in the field of view can be done via imaging technique, for the GRM the use of non-transients sources for calibration purposes can be done via the occultation technique, which requires a careful modelling of the background. In this work we propose a parametric model for the GRM background that is based on simulations of the three main components (CXB, Reflection and Albedo) along the orbit. We show that this is the most suitable model to correctly estimate the flux of steady sources in the GRM field of view, and we apply it to the in-flight observations of the Crab Nebula.

Speaker: Maria Grazia Bernardini (Istituto Nazionale di Astrofisica (INAF))

Poster_modelP.pdf

14:21 Investigating High-Energy Time Lags in Gamma-Ray Bursts with Fermi-LAT and GBM

Time lags between the arrival time of different photon energies provide valuable insight into the emission mechanisms of Gamma-Ray Bursts (GRBs). Using data from the Fermi Gamma-ray Burst Monitor (GBM, between 10 - 500 keV) and the Large Area Telescope (LAT), particularly those obtained with the Low Energy (LLE) technique (30 - 100 MeV), we analyze a sample of 70 GRBs to investigate the relationship between spectral lags and high-energy emission properties. Lags within the GBM energy range (10 keV – 1 MeV) are predominantly positive (76%), namely lower-energy photons arrive later than higher-energy ones as a possible consequence of a hard to soft spectral evolution. However, when comparing LLE (30–100 MeV) and GBM bands, in 37% of cases high-energy photons are delayed relative to low-energy ones. These negative lags can be interpreted as due to an additional spectral component rising in the LLE energy range as supported by the spectral analysis of these events.

Speaker: Ms Claudia Maraventano (Università di Palermo)

poster_swift.pdf

14:22 Astro-COLIBRI

Observations of transient phenomena, such as GRBs, FRBs, novae/supernovae explosions, coupled with the detection of cosmic messengers like high-energy neutrinos and gravitational waves, have transformed astrophysics. Maximizing the discovery potential necessitates tools for swiftly acquiring an overview of the most relevant information for each new detection. Introducing Astro-COLIBRI, a comprehensive platform designed to meet this challenge.

Astro-COLIBRI features a public API, real-time databases, alert systems, discussion forums, and iOS/Android apps as well as a web-app as user clients. In real time, it evaluates incoming astronomical observation messages from all (!) available alert streams, filters them based on user-defined criteria, and contextualizes them in the multi-wavelength (MWL) and multi-messenger (MM) context. User clients offer a graphical representation, providing a succinct summary for quick identification of interesting phenomena, assessing observing conditions globally, and more. They make use of Swift ressources to allow the timely creation of lightcurves of GRBs in context of archival data.

This (poster) contribution presents the key features of Astro-COLIBRI, outlining its architecture, summarizing data resources, and show-casing some examplary use-cases.

Speaker: Dr Fabian Schussler (CEA Irfu DPhP)

Astro-COLIBRI_poster_small.pdf

14:24 Peculiar X-ray properties of MAXI J1631-479 and their understanding

MAXI J1631-479 is a bright black hole X-ray transient discovered in 2018. MAXI-GSC and Swift-XRT data does not show a typical q-shape but an inverse Y-shape in the hardness and intensity diagram (HID) during the course of the outburst. Using MAXI and Swift data, we demonstrate such an inverse Y-shape and observed various states, low/hard, hard and soft intermediate, and high/soft states, are naturally explained by current accretion disk models. We also point out and discuss other peculiar properties commonly observed in such inverse Y-shape sources, e.g., MAXI J1535-571, from MAXI and Swift observations.

Speaker: Prof. Hitoshi Negoro (Nihon University)

negoro_hitoshi.pdf

14:25 The GRB quick analysis pipeline of SVOM ECLAIRs and GRM

The SVOM (Space-based multi-band astronomical Variable Objects Monitor) observatory is dedicated to the exploration and progress of Gamma-Ray Burst (GRB) science. The two wide field of view instruments on board the satellite – ECLAIRs and GRM – are currently monitoring the transient sky and detecting GRBs in both X- and gamma-ray energy bands (from 4 keV to 5 MeV, jointly). In addition to GRB onboard position and alert time which are publicly broadcasted in real time by the SVOM French Science Center (FSC), quick scientific products are generated by the eclgrm-vhf pipeline from the ECLAIRs and GRM count light curves that are immediately transmitted to the ground through a VHF channel. In this work, we present the architecture of the eclgrm-vhf pipeline running at FSC, and the computation of these scientific products (durations, peak fluxes, ground significance, hardness ratios, event classification), which will be made public following each GRB alert.

Speaker: T. Maiolino (Laboratoire Univers et Particules de Montpellier (LUPM) - CNRS/UMR5299)

Swift20YearsPoster_ECLGRMVHF_TMaiolino.pdf

14:26 Multi-wavelength properties of short GRBs with extended emission observed by Swift

We present a detailed study of the multi-wavelength properties of a sample of short GRBs with extended emission (EE) observed by Swift. The sample consists of 11 events, selected from the SBAT4 catalog by D’Avanzo et al., (2014), which was subsequently expanded to include events up to 2021. This sample exclusively contains only short GRBs with favorable observational conditions for the determination of redshifts from Earth and bright in terms of observed peak flux in the BAT energy band. The properties of the prompt emission (hardness ratio, spectral evolution), as well as the temporal behaviour of the X-ray afterglow phase are compared to the genuine short GRBs of the SBAT4 sample, and with a similarly selected complete sample of long Swift GRBs (BAT6), with the aim of identifying unique features that distinguish the class of short GRBs with EE.

Speaker: Michela Maria Dinatolo (Istituto Nazionale di Astrofisica (INAF))

Dinatolo_Michela_Maria.pdf

14:27 X-ray Obscuration vs molecular gas distribution in local AGN

We present a study aiming at measuring the correlation between X-ray absorption and absorption due to the presence of molecular gas from larger scales in the host galaxies of nearby AGN. The study will be carried out through the hard X-ray selected AGN in the IBIS AGN CO survey (IBISCO), focussing in particular on those AGN identified as “ideal targets”, i.e. those where there are indications that structures in the host galaxy (i.e. edge-on configuration, bars, rings, dust lanes, filaments, merging events) can significantly contribute to the total amount of absorption measured in the X- rays. For the X-ray absorption measurements, we use mainly broad-band spectra obtained by Swift-XRT in conjunction with high energy data (NuSTAR/INTEGRAL) both from archival and proprietary observations, while in the sub-mm regime we employ available ALMA and NOEMA (proprietary and archival) dat, as well as IRAM (30cm) data. ALMA and NOEMA data are spatially resolved and are crucial in order to reveal gas/dust structures not visible in the optical; they also allow to study the absorption spatial variability. IRAM data can instead give an overall estimate of the gas in the nuclear regions.

Speaker: Manuela Molina (IASF/Istituto Nazionale di Astrofisica (INAF))

molina_manuela.pdf

14:28 Gamma-ray burst pulse structures and emission mechanisms

The prompt phase X- and γ-ray light curves of gamma-ray bursts (GRBs) exhibit erratic and complex behaviour, often with multiple pulses. The temporal shape of individual pulses is often modelled as ‘fast rise exponential decay’ (FRED). Here, we introduce a novel fitting function to quantify pulse asymmetry. We conduct a light curve and a time-resolved spectral analysis on 61 pulses from 22 GRBs detected by the Fermi Gamma-ray Burst Monitor. Contrary to previous claims, we find that only ∼ 50% of pulse light curves in our sample show a FRED shape, while about 25% have a symmetric light curve, and the other 25% have a mixed shape. Furthermore, our analysis reveals a clear trend: in multi-pulse bursts, the initial pulse tends to exhibit the most symmetric light curve, while subsequent pulses become increasingly asymmetric, adopting a more FRED-like shape. Additionally, we correlate the temporal and spectral shapes of the pulses. By fitting the spectra with the classical “Band” function, we find a moderate positive Spearman correlation index of 0.23 between pulse asymmetry and the low-energy spectral index α_max (the maximum value across all time bins covering an individual pulse). Thus, during GRB light curves, the pulses tend to get more asymmetric and spectrally
softer with time. We interpret this as a transition in the dominant emission mechanism from photospheric (symmetric-like and hard) to non-thermal emission above the photosphere and show that this interpretation aligns with a GRB jet Lorentz factor of the order of a few 10s in many cases.

Speaker: Gowri A (IUCAA, Pune)

gowri_poster_2025_inaf_finalv.pdf

14:29 "Improving transient identification with Swift-XRT"

The Living Swift-XRT Point Source Catalogue (LSXPS) is a unique facility: it is updated in near real-time, enabling a sensitive, “live” search for new high-energy transients. This opens up a new area of transient phase-space for exploration, as evidenced by the LSXPS discovery of the enigmatic event Swift J0230. However, the majority of transient candidates detected are faint, classified as “low significance” transients within LSXPS; determining which of these are actually transient, especially where they are close to the XRT detection limit and consequently impacted by the Eddington bias, poses a significant challenge. We present a simulation-based approach which yields confidence intervals on source flux, corrected for the Eddington bias and accounting for the increasing number-density of sources at lower fluxes. This enables more reliable identification of true transients and rejection of those whose apparently increased flux is a measurement effect. Currently, LSXPS has detected approximately 8000 transients, with about 2400 classified as low significance . Improving the categorization of even 10% of these detections could significantly enhance the catalog's quality and reliability.
This technique will shortly be incorporated into the real-time LSXPS analysis and we discuss the expected impact on transient detection rates and the potential impact on high-energy transient astronomy in the TDAMM era.

Speaker: Srijan Srivastava (University of Leicester, UK)

Srivastava_Srijan.pdf

14:29 20 years of Swift observations of Short Gamma-Ray Bursts.

Before the launch of the Neil Gehrels Swift observatory, little was known about the origin of short Gamma-ray Burst. While the short duration of the high-energy emission pointed out to a merger of compact objects, proof was lacking, and nothing was known about the afterglow emission.
At this conference, I will briefly discuss how Swift, thanks to the the unique capability of autonomous repointing, early start of observations, and sensitivity, enabled the community to find short GRB afterglows and define short GRBs general properties such as energy, galaxies, offsets, environment. I will also summarize how Swift/UVOT permitted the study of peculiar and watershed events such as the kilonova in the short GRB 170817A, counterpart to the gravitational wave source GW 170817, and other similar bursts.

Speaker: Massimiliano De Pasquale (Universita' di Messina and Istituto Nazionale di Astrofisica (INAF))

Poster - Firenze - Swift and sGRBs - De Pasquale - 3.pdf

14:29 3D Simulations of sGRB Jets: Ballistic Regime and Afterglow Emission

I will present 3D relativistic magnetohydrodynamic simulations of incipient Gamma-Ray Burst (GRB) jets piercing through realistic binary neutron star merger environments.
Applying the methods we developed to extend the 3D jet evolution up to tens of seconds without loss of resolution, we are able to reach a nearly ballistic expansion regime, with most of the jet energy converted into kinetic form and an angular structure that is no longer evolving. The final outcome of the evolution provides reliable input for afterglow emission modeling, allowing us to compare the corresponding light curves with the rich dataset of GRB 170817A.
By varying jet injection parameters such as luminosity, engine duration, magnetization, and jet launching time with respect to merger, we explore a range of models and study how the different parameters affect the jet breakout, larger scale propagation, and afterglow emission.

Speaker: Ms Emma Dreas (SISSA - Scuola Internazionale Superiore di Studi Avanzati)

Dreas_Emma.pdf

14:29 A millimeter rebrightening in GRB 210702A

We present X-ray to radio frequency observations of the bright long gamma-ray burst GRB 210702A. Our ALMA observations show a significant rebrightening by a factor of approximately 2 beginning at 8.2 days post-burst and rising to peak brightness at 18.1 days before declining again. This is the first such rebrightening seen in a millimeter afterglow light curve. A standard forward shock model in a stellar wind circumburst medium can explain most of our X-ray, optical, and millimeter observations prior to the rebrightening, but significantly overpredicts the self-absorbed radio emission, and cannot explain the millimeter rebrightening. We investigate possible explanations for the millimeter rebrightening, and that energy injection or a reverse shock from a late-time shell collision are plausible causes. Our observations demonstrate that millimeter light curves can exhibit some of the rich features more commonly seen in optical and X-ray afterglow light curves, motivating further millimeter wavelength studies of GRB afterglows.

Speaker: Simon de Wet (Technical University of Denmark)

swift20_simon_dewet.pdf

14:29 A study of GRB mechanisms through an automatic modelling of all Swift XRT light curves

Gamma-ray burst light curves exhibit a wide range of temporal shapes, and understanding these features may help to understand the progenitors and processes involved in the prompt afterglow emission. We present laff, a code to automatically fit Swift-XRT GRB afterglow light curves, identifying and modelling both the flares with fast-rise exponential-decay peaks, and the underlying fading afterglow with a series of broken power laws. With this code, we present a systematic study, fitting all Swift-XRT light curves to date, producing a catalogue of fitted flare and afterglow parameters. In this talk, we demonstrate correlations and results of these parameters, and discuss how this can be used to establish investigations in several areas of GRB physics: we use the modelling of high energy X-ray flares to search for the possibility of prompt coherent radio flares as a means of investigating the GRB jet composition, and the identification of progenitors through modelled flare and afterglow characteristics combined with the classification of prompt emission with machine learning.

Speaker: Adam Hennessy (University of Leicester)

14:29 An Hubble constant estimation via electromagnetic and gravitational-wave joint analyses

In August 2017, the groundbreaking observation of GW170817 marked the first-ever identification of a binary neutron star merger, accompanied by the detection of a Gravitational Wave (GW) and a gamma-ray burst (GRB). The GRB exhibited prompt gamma-ray emission and an afterglow across radio, optical, and X-ray bands, originating from a relativistic jet formed post-merger at an angle of 20-30 degrees from its axis. In this work, we estimate the Hubble constant H0 using broad-band afterglow emission and relativistic jet motion from the Very Long Baseline Interferometry and Hubble Space Telescope images of GW170817. Using a simultaneous fit of GW and afterglow, we probe the H0 measurement robustness depending on the data set used, the assumed jet model, the possible presence of a late time flux excess. Using the sole GW leads to a 20% error (77+21-10 km/s/Mpc, medians, 16th-84th percentiles), because of the degeneracy between viewing angle and luminosity distance. Adding the afterglow light curve and centroid motion in the analysis efficiently breaks parameters degeneracies and overcome the late-time deviations, giving H0 = 69.0+4.4-4.3 km/s/Mpc (in agreement with Planck and SH0ES measurements) and a viewing angle of 18.2+1.2-1.5 deg. This is valid regardless of the jet structure assumption.

Speaker: Giulia Gianfagna (Istituto Nazionale di Astrofisica (INAF), Istituto di Astrofisica e Planetologia Spaziali (IAPS))

Poster_GW170817_Swift_Gianfagna.pdf

14:29 Automated optical follow-up of Swift GRBs with Palomar-60 inch telescope

The Palomar 60-inch (1.5 metre) telescope, P60, conducted an automated optical GRB follow-up programme from 2005 to 2017. P60 was able to respond automatically, in less than three minutes, to well-localised Swift GRB alerts, and it was one of the largest optical telescopes with such a programme. The automatic response to the alerts built an unbiased GRB afterglow sample, making it a valuable tool for investigating the entirety of the GRB population. This talk presents results from the first analysis of the full 13-year long sample of GRB afterglows observed within one hour of Swift trigger, including the investigation into decay and spectral parameters of P60 afterglows, as well as their time-dependent optical luminosity function. The full dataset, along with data from other facilities, will be used to characterize GRB jet properties, such as energy ranges or opening angles, as well as the true rates of relativistic jets.

Speaker: Aleksandra Bochenek (Astrophysics Research Institute, Liverpool John Moores University)

abochenek_swift_p60_poster.pdf

14:29 Characterisation of the early X-ray emission of short Gamma-Ray Bursts

Over its 20 years of operation, the Swift satellite has led to breakthrough discoveries in the study of Gamma-Ray Bursts (GRBs). In particular, the rapid and automatic repointing capabilities of the X-Ray Telescope (XRT) have enabled the detection and localisation of the GRB afterglow in about one minute after the trigger provided by the Burst Alert Telescope (BAT). XRT observations have unveiled common features in soft X-ray lightcurves, such as steep decays and plateaus, whose physical origin remains poorly understood. These features cannot be explained within the standard afterglow model, which attributes the emission to electrons cooling via synchrotron and inverse Compton processes at the forward shock. The steep decay phase is also observed in a fraction of the short GRBs. Since the steep decay emission is significantly brighter than the forward shock emission, short GRBs provide a unique opportunity to observe it for a longer duration (up to 10-15 minutes) than long GRBs. In this talk, I will present a systematic analysis of early X-ray emission of short GRBs, including their temporal and spectral evolution. I will introduce a new technique to model the curvature and the intrinsic evolution of the GRB spectrum in XRT data. This work aims to understand the physics driving the steep decay phase and to optimise the detection strategies with current and future observatories.

Speaker: Annarita Ierardi (Gran Sasso Science Institute)

14:29 CHIPS: a Cubesat for cutting-edge scientific investigations

The CHIPS team aims to develop, build and launch the first cryogenic infrared space telescope on a CubeSat, enabling cutting-edge scientific investigations that have been traditionally restricted to larger and substantially more expensive missions. Thanks to its near-infrared sensitivity, ultra-stable image quality in four simultaneously exposed filter bands, and rapid spacecraft slewing, CHIPS (Cubesat with HIgh Performance for Skyhopper) will be a facility to (1) identify and study Gamma Ray Burst (GRB) afterglows originating all the way back to the edge of the observable Universe, (2) to probe electromagnetic infrared counterparts of gravitational waves. CHIPS will also demonstrate science return in other areas of astrophysics, including the characterisation of Near-Earth Objects to investigate planetary system formation, the discovery of potentially habitable Earth-size exoplanets transiting in front of nearby cool stars, and pave the way to develop future constellations of distributed-aperture space telescopes. In this talk we will describe the status of the project - close to the Preliminary Requirements Review deadline - and analyse the technology innovations of the proposed mission.

Speaker: Andrea Melandri (Istituto Nazionale di Astrofisica (INAF))

CHIPS_Melandri.pdf

14:29 Cosmology with Gamma-Ray Bursts: status and perspectives

The huge luminosity, redshift distribution extending to $z > 9$ and association with the explosive death of very massive stars make long GRBs uniquely powerful cosmic beacons to unveil and characterize the bulk population of low mass / lumninosity primordial galaxies, assess star formation rate evolution up to the first generation of stars (pop–III), shed light on the sources and evolution of cosmic reionization. At the same time,the Ep,i - Eiso ("Amati") and other correlations between prompt and early afterglow emission of GRBs are intensively used for measuring the expansion rate and geometry of the Universe, investigating the nature and evolution of ”dark energy” and testing non-standard cosmological models. Finally, short GRBs produced by the merging of NS-NS and NS-BH systems, sources of Gravitational Wave signals, are a key phenomenon for enabling multi-messenger cosmology. I will shortly review the status and perspectives of this very hot research field, including the Swift cornerstone contributions and the expected performances of space mission projects, like THESEUS, aiming at fully exploiting the potentialities of the GRB phenomenon for cosmology in synergy with the large e.m. (e.g., ELT, TMT, SKA, CTA, NewATHENA) and multi-messenger (e.g., ET, CE, Km3NET) facilities of the future.

Speaker: Lorenzo Amati (Istituto Nazionale di Astrofisica (INAF))

14:29 Direct metallicity measurement of the host galaxy of GRB 050505 at z=4.28 using JWST/NIRSpec

Metallicity plays a key role in the evolution of stars, and obtaining accurate gas-phase metallicity measurements are therefore also important when studying the progenitors of stellar explosions, such as supernovae and gamma ray bursts (GRBs). However, there are well known limitations in how well the metallicity of galaxies can be measured, predominantly related to the quality of the generally indirect diagnostics that are employed.

The metallicity of the ionised gas within star forming regions can be measured from emission line spectra, ideally using weak and temperature-sensitive auroral lines, but more generally using indirect and model dependent relations between strong line ratios and metallicity. On the other hand, GRBs offer a direct probe of the metallicity of the host galaxy neutral interstellar gas from absorption lines imprinted on afterglow spectra. However, absorption and strong emission line metallicities often disagree by up to a factor of three for the same galaxy, and it is unclear whether this is due to intrinsic differences in the metallicity of the neutral and ionised gas, or due to inaccuracies in the diagnostics. We need to understand the origin of these discrepancies in order to optimise on the use of GRBs as probes of the interstellar medium of distant galaxies.

In this talk we present the first GRB host galaxy with a measured absorption line and direct emission line metallicity, using the temperature sensitive [OIII]$\lambda$4363 auroral line detected in the JWST/NIRSpec spectrum of the host of GRB 050505 at z=4.28. We find that the absorption line metallicity is in good agreement with the temperature-based emission line metallicity, both of which are ~0.2 dex lower than the strong emission line metallicity, even when using the strong line relations calibrated to high redshift galaxies. Our results imply that, at least at high redshift, GRB afterglow absorption lines trace more accurately the metallicity of star forming regions than strong emission line diagnostics, although this will need to be confirmed with larger samples.

Speaker: Anne Inkenhaag (University of Bath, United Kingdom)

Inkenhaag_Anne.pdf

14:29 Distribution of the number of pulses within a long gamma-ray burst

Time profiles of GRB prompt emission are still far from being understood, despite intensive efforts to characterise them in terms of duration, hardness ratio, minimum variability timescale, averaged and individual power density spectra. Surprisingly, the number of peaks that one could observe in a GRB light curve has mostly been overlooked.
For the first time, we studied and modelled the distribution of the number of peaks within each GRB across five major GRB catalogues, namely CGRO/BATSE, BeppoSAX/GRBM, Swift/BAT, Insight-HXMT, and Fermi/GBM, encompassing over 6000 GRBs and 20,000 peaks. We found that this distribution can be consistently modelled with a mixture of two exponentials, dividing GRBs in two classes, so-called "peak-rich" (20%) and "peak-poor" (80%) GRBs. Peak-rich GRBs exhibit sub-second variability on top of a slowly varying component, while peak-poor GRBs show only the latter.
We discuss the implications on the theoretical models that have been proposed to explain the variety and properties of GRB time profiles.

Speaker: Romain Loic Maccary (Istituto Nazionale di Astrofisica (INAF))

_Poster__Template_Swift_conference.pdf

14:29 Do Long Gamma-Ray Burst Engines Speak a Stochastic or Deterministic Language?

A successful description of the inner engine activity of long gamma-ray bursts (LGRBs) holds the key to deciphering the variety and complexity exhibited by their light curves (LCs). Although the knowledge of GRB spectral properties has made huge strides thanks to technological advancement, temporal properties remain mostly unintelligible. In particular, an open question is whether they originate from deterministic (e.g., presence of periodic components?) or stochastic processes. In this respect, we present a common description of LGRB LCs as the outcome of a stochastic pulse-avalanche process, resulting from the refinement of a previous model (Bazzanini et al. 2024). The model parameters were optimised with a genetic algorithm, and tested on three independent datasets of LGRBs detected by three different experiments: Swift/BAT, CGRO/BATSE, and Fermi/GBM. We found that a simple pulse-avalanche process operating in a nearly critical regime can successfully reproduce several average temporal properties of the population of real LCs, providing clues to the dynamical behaviour of the LGRB inner engine. In addition, this model offers a credible tool to simulate from scratch synthetic LCs for future experiments.

Bazzanini et al. 2024, A&A, 89, A266

Speaker: Mr Manuele Maistrello (University of Ferrara)

maistrello_manuele.pdf

14:29 Envisioning Tomorrow: INAF prospects and challenges for multimessenger astronomy in the era of the next electromagnetic future facilities

INAF will play a key role in the newborn multi-messenger astronomy field allowing us to study and identify the likely faint and rapidly fading electromagnetic counterparts of the hundreds gravitational wave (GW) events expected by the 2nd generation GW detectors network at full sensitivity together with upcoming electromagnetic facilities like Rubin telescope.
In this talk, I will present all the activities we are carrying out to optimize the response of the Italian and European network of facilities to expected GW triggers, and how the team is working in the context of the search for electromagnetic counterparts of GW sources and their spectroscopic characterization, also in anticipation of the arrival of the Einstein Telescope, in which our large community is involved.
All the activities are expected to provide means and opportunities to the Italian and European astronomical communities to have a leading role in the GW and Time Domain Astronomy.

Speaker: Silvia Piranomonte (Istituto Nazionale di Astrofisica (INAF))

Opt_NIR counterparts of gravitational wave sources in the Rubin_ET era - Piranomonte (2).pdf

14:29 Exploring BeXRBs Major Outbursts: Insights from X-ray and Optical Variability

The Magellanic Clouds (MCs) provide an unparalleled laboratory for studying high-mass X-ray binaries (HMXBs) due to their moderate, well-constrained distances and relative isolation from the Galactic plane. Among these systems, Be X-ray binaries (BeXRBs) – featuring Be-type stars as donor companions – stand out for their remarkable variability, including prominent outbursts in both X-ray and optical wavelengths. Systems in the MCs are particularly valuable for investigating super-Eddington accretion during major X-ray outbursts, as similarly bright events are perhaps only seen in Galactic BeXRB pulsar Swift J0243.6+6124.

Recent advances, enabled by extensive monitoring through X-ray observatories such as Swift and the optical OGLE survey, have provided unique datasets for analyzing major outbursts over the past decade. In this talk, I will present findings on the super-Eddington regime in BeXRBs, including constraints on neutron star magnetic fields and system orbital parameters through the application of torque models. Additionally, I will examine the relationship between X-ray and optical variability observed during these events, offering new insights into the mechanisms driving the extreme behavior of these remarkable astrophysical systems.

Speaker: Georgios Vasilopoulos (National and Kapodistrian University of Athens)

Poster_Swift20years_reflection.pdf

14:29 Exploring HXMB with the BAT survey data. Results and legacy.

The continuous sky monitoring performed by the Burst Alert Telescope has allowed for the foundation of a huge data archive in the 15-150 keV band. The exploitation of these data set has been particularly fruitful for the study of the long term spectral and timing properties of high mass x-ray binaries. In this talk we present an overview of the main findings obtained along the 20 years of the Neil Gehrels Swift Observatory all sky observation.

Speaker: Valentina La Parola (Istituto Nazionale di Astrofisica (INAF))

14:29 Exploring Origin of Ultra-Long Gamma-ray Bursts: Lessons from GRB 221009A (the "BOAT")

GRB 221009A stood out as the brightest GRB detected to date, offering a remarkable opportunity to delve into the intricacies of GRB physics. In this work, we investigated the prompt emission and afterglow characteristics of this unique burst utilizing observations from several missions like Swift, Fermi, and INTEGRAL including our early photometric (prior prompt emission) and spectroscopic observations taken using various telescopes. High-energy results show an ultra-long GRB (ULGRB) nature, with a prompt emission duration exceeding 1000 s. We examined its origin (through observations and simulation in MESA) and central engine and compared it with a nearly complete sample (categorizing the sample to Bronze, Silver, and Gold based on T90 duration) of Swift-detected GRBs with measured redshifts. Notably, the Gold sub-sample (a higher likelihood of being ULGRB candidates, including the "BOAT") suggests a collapsar scenario with a hyper-accreting black hole as a potential central engine. Our early optical observations during the prompt emission of GRB 221009A help to discard the presence of any bright optical emission with internal or external origin. We determine the distance to GRB 221009A through spectroscopy (taken with 10.4m GTC) of absorption and emission lines and establish the burst to be associated with a star-forming galaxy. Additionally, we conducted a comparative analysis of the properties of host galaxies associated with TeV-detected bursts including the BOAT, to acquire insights into the environments of TeV GRBs.

Speaker: Rahul Gupta (NASA GSFC)

Gupta_Rahul.pdf

14:29 Exploring the deep Universe: A study of GRB 240218A @ z = 6.78

The detection and follow-up observations of high-redshift (z > 6) gamma-ray bursts (GRBs) provide a unique opportunity to explore the properties of the distant Universe. GRB\,240218A, discovered by Swift/BAT, is one of the few identified so far, and with a redshift of $z=6.782$ is the burst with the second highest spectroscopic $z$ measured to date. Following the detection by high-energy satellites, several ground-based observations from 68 s to $\sim48$ d after the detection have been secured, from the optical to the radio band.
I will present these broad-band, multi-epoch observations, which allowed us to perform a comprehensive study of the emission
and physical properties of this event. Specifically, we studied the temporal evolution of the X-ray, NIR and radio light curves, and we investigated the spectral energy distribution (SED) at different times to trace the possible spectral evolution. We also compared the prompt phase properties, X-ray luminosity and optical extinction of GRB\,240218A with those of the long-duration GRBs (LGRBs) population, both at high and low redshift.
The SED analysis revealed a typical afterglow-like behaviour at late times. The origin of the early-time emission is uncertain, with the possible presence of an additional contribution on top of the afterglow emission. The broad-band physical modelling of the afterglow is consistent with a narrow Gaussian jet seen slightly off-axis, with $\theta_v=2.52^{+0.57}_{−0.29}$ deg, and with the presence of a jet break $\sim0.86$ d after the trigger. In addition, we identified a narrow jet opening angle consistently with other high-z bursts, possibly pointing to the presence of more collimated jets at high redshift.
This discovery increased the limited sample of $z>6$ GRBs discovered to date, and gave the opportunity to compare them with the population of bursts at any distances. Moreover, it highlights the unique role of high-redshift GRBs like GRB\,240218A in probing the properties of the early Universe, offering critical insights into jet structure, energetics, and the evolution of GRBs across cosmic time.

Speaker: Riccardo Brivio (Istituto Nazionale di Astrofisica (INAF))

Poster_0218A.pdf

14:29 Exploring the long GRB population using Swift BAT6 sample

Due to the large number of Swift GRB detections, it has been possible to select sub-samples of long GRBs that are reasonably complete in redshift and with observed prompt and afterglow emission. We perform Bayesian inference to constrain the distributions of burst parameters of the population, in accordance with the observed physical properties of the BAT6 sample. We use the structured jet models in our analysis package Afterglowpy to model the distribution of afterglow observations for the sample. Applying this to observations at key times in the X-ray, optical and radio domains, we create an observationally-calibrated tool for population synthesis modelling. From this, we derive population predictions for afterglow observations including Inverse Compton features in the TeV regime.

Speaker: Mx Jianghui Yuan (University of Bath)

poster.pdf

14:29 First version of a Fink filter to identify Orphan Gamma-Ray Burst Afterglows among the Rubin LSST data

Gamma-Ray Bursts (GRBs) rank among the most energetic phenomena in the Universe. Thanks to the Swift and Fermi observatories, significant progress has been made in GRB science over the past decades, but one area of research that now requires exploration are the still elusive GRB orphan afterglows. We define orphan afterglows as GRB afterglows viewed off-axis, which have hence a negligible gamma-ray flux. They are promising candidates to learn more about GRB physics, jets and progenitors, as well as for the development of multi-messenger astrophysics with gravitational waves.

So far, only a few orphan afterglow candidates have been found, but the Rubin Observatory is expected to enhance the detection of these faint sources thanks to its large field of view, large mirror and survey mode operations. In this presentation, we will show our work done in order to find orphan afterglows in the Rubin wide, fast, deep survey. To identify orphan afterglows, we used the characteristic features of their light curves that we computed within the framework of the forward shock model associated with electron synchrotron emission. We first generated robust populations of GRBs based on Swift catalogues, and simulated their off-axis afterglow light curves using afterglowpy (Ryan et al., 2020). We simulated their detection by Rubin LSST in order to extract various light curve features. In addition, we designed a new method to fit the light curves with observations in multiple bands by renormalising the bands to the r-band. We developed a high-performance machine learning filter capable of discriminating these rare orphan-like events from all other variable objects.

We will present the performance of our filter as implemented in the Fink broker and tested on the ELAsTiCC (first simulation of Rubin LSST alerts, with millions of synthetic transient light curves and host galaxies) data set and our own Rubin observation simulations of orphan afterglows. Our code is open-source, implemented in Fink, and ready to receive the first Rubin data expected in the coming months.

Speaker: Marina Masson (LPSC IN2P3 CNRS)

MASSON_Marina_orphan_afterglows.pdf

14:29 From $\textit{Swift}$/GROND to SVOM/COLIBRI to study the GRB afterglow

We are now in the era of rapid-response observations of gamma-ray bursts (GRBs). Multiwavelength observations are essential in GRB and other transient phenomena studies. A rapid follow-up is crucial as the analysis of the GRB afterglow properties may be impacted by its rapid fade. Early-time observations taken with the onboard Neil Gehrels Swift Observatory ($\textit{Swift}$) instruments enable the study of GRBs up to the epoch of reionization. In addition, ground-based telescopes such as the seven-band filter Gamma-Ray Optical and Near-Infrared Detector (GROND) have a high enough sensitivity and wide-band coverage for studying high extinguished and redshifted GRBs. The combination of such observations provides us with high signal-to-noise spectral energy distributions of GRB afterglows that allow us to study different properties of their host galaxy. Launched in 22$^{nd}$, June 2024 from the Xichang launch base, the Space-based multi-band astronomical Variable Objects Monitor mission (SVOM) provides a versatile satellite equipped with multiwavelength instruments. The orbit and pointing strategy of the satellite have been thought to maximize the GRB detection rate of ground-based telescopes operating at optical and NIR wavelengths. These SVOM space and ground-based facility synergies are consolidated by the building of a dedicated and coordinated follow-up segment with robotic telescopes including the 1.3m COLIBRI (in Mexico) and the C-GFT 1.2m (in China) telescopes. In particular, COLIBRI, which was inaugurated on 7$^{th}$, September 2024 at the San Pedro Mártir National Astronomical Observatory, Mexico, will be able to observe the sky with the DDRAGO two channels camera ($\textit{gri}$ and $\textit{zy}$ filters) and the CAGIRE infrared camera ($\textit{JH}$ filters). Although the $\textit{K}$-band is absent, the COLIBRI instrument configuration is quite similar to GROND, while offering a significantly wider field of view of 26 arcminutes and a response time of less than 20 seconds from one alert to an observation. This capability will enable rapid photometric redshift estimates up to high redshifts. In addition, the association of the SVOM instruments with COLIBRI will allow us to study the color evolution of GRB afterglows and characterize the effect of the dust extinction from their host galaxies during the next decade.

Speaker: Ny Avo RAKOTONDRAINIBE (Laboratoire d'Astrophysique de Marseille)

grbafterglowsintheSVOMCOLIBRIera_NR.pdf

14:29 GRB 241030A and its Super-Flare

Over the last 20 years, the Neil Gehrels Swift Observatory has provided an unprecedented multiwavelength view into the origins and properties of gamma-ray bursts (GRBs). Even after having observed over 1,500 bursts, Swift continues to detect GRBs with intriguing and unique behaviors. Here we present the long GRB 241030A (at redshift z=1.4) which displayed a "super-flare", with ~4x the fluence of the prompt emission observed by the BAT, rapid spectral variability on timescales of tens of seconds, and a temporal evolution of the peak energy. We will discuss the implications of these findings in the context of GRB emission mechanisms and their broader impact on understanding the physics of relativistic jets.

Speaker: Noel Klingler (NASA-GSFC / UMBC / CRESST II)

14:29 Insight on GRB physics from a novel data driven method for systematic analysis of X-ray light-curves

Gamma-ray bursts (GRBs) exhibit a rich variety of X-ray lightcurve behaviors, including flares and plateau/shallow decay phases, whose origins remain debated. Existing studies often rely on diverse analysis techniques applied to limited GRB samples, leading to results that may be difficult to generalize. In this study, we introduce a new data-driven, model-independent method for automatically analyzing the Swift XRT dataset. This approach enables a consistent and comprehensive characterization of GRB afterglow X-ray lightcurves, covering an order of magnitude more events than previous studies. By providing a unified framework for large-scale analysis, this method opens new avenues for identifying robust trends and understanding the physical processes shaping GRB lightcurve evolution.

Speaker: Alessandro Armando Vigliano (University of Trieste - INFN Trieste)

Vigliano_Alessandro.pdf

14:29 Joint observation of GRBs detected by BeppoSAX/WFC and Konus-Wind

We present time-averaged and time-resolved (where possible) spectral analysis of prompt emission of a dozen GRBs (including GRB 990123) simultaneously detected by Konus-Wind and BeppoSAX/WFC instruments. Modelling the prompt emission spectra recorded in a wide energy range with the empirical functions is discussed in the context of thermal and non-thermal origin of emission.

Speaker: Anastasia Tsvetkova (University of Cagliari, Department of Physics)

Tsvetkova_Anastasia.pdf

14:29 LeHaMoC: an open-source leptohadronic code for multi-messenger modeling

Recent associations of high-energy neutrinos with active galactic nuclei (AGN) have rekindled interest in leptohadronic models of radiation from astrophysical sources. The rapid growth in multi-messenger data acquisition highlights an emerging need for fast numerical models capable of application to large source samples. In this contribution, we introduce LeHaMoC, an open-source, versatile leptohadronic code. LeHaMoC is specifically designed for modeling time-variable, non-thermal emission from compact astrophysical sources, including blazar jets, AGN coronae, and gamma-ray bursts (GRBs). We showcase recent applications, such as blazar SED fitting using Bayesian inference techniques, modeling X-ray and γ-ray variability in blazars, and exploring high-energy neutrino associations. Additionally, we discuss its role in training deep neural networks - an essential step toward achieving more efficient computations and exploring larger parameter spaces.

Speaker: Despina Karavola (University of Athens)

LeHaMoC_Poster_Swift.pdf

14:29 Lessons from the Swift XRT GRB sample: from scale-invariance to light curve flux spread and from plateau correlations to reverse shock properties

A large and growing sample of Swift XRT observations allows us to draw conclusions about the population properties of GRBs. I will present two examples of this. One builds on the scale-free nature of GRB afterglow dynamics and synchrotron spectra, deploying scale-invariance to interpret the spread of observed fluxes when binned by light-curve slope at the time of observation. This spread is found to increase with increasing light-curve slope. According to the scaling relations, this pattern is inconsistent with a large spread in environment densities if these were the dominant factor determining the variability of light curves. The other, earlier published, example uses the known correlations between afterglow plateau end times and flux levels, both in X-rays and optical, to show that GRB plateaus are consistent with the "thick shell" model but not with "thin shell" models for reverse shocks.

Speaker: Hendrik van Eerten (University of Bath)

VanEerten_Hendrik.pdf

14:29 Long-Term X-ray Activity of GRS 1915+105 studied with Swift and MAXI

GRS 1915+105 is one of the brightest black hole X-ray binaries (BHXBs) since it was first detected by GRANAT/WATCH in 1992 until it faded into a quiescent state in recent years. We studied its long-term activity using MAXI/GSC and Swift/BAT data for the duration of 2009 – 2019, the last ten years of its active state. We found that the 10 years’ activity of GRS 1915+105 can be classified into four distinct spectral branches in the hardness-intensity diagram drawn with the MAXI/GSC and Swift/BAT bands. We named these branches the diagonal branch, the soft branch, the faint branch, and the quiescent branch based on their positions in the diagram. These branched can be also identified in the X-ray light curves, with each of them lasting for months to years. Although it is not straightforward to compare it with the “spectral states” found in the canonical “q-shaped” hardness intensity diagram often drawn for the outbursts of transient BHXBs, we find that the soft branch of GRS 1915+105 has similarities to the high/soft state of canonical BHXBs where the disk emission is dominant, while the faint branch is like the low/hard state where corona emission dominates. The diagonal branch, however, is difficult to interpret in the standard framework of BHXBs.
We can extend this study using the light curves of RXTE/ASM, Swift/BAT and CGRO/BATSE in the preceding periods 1992 – 2009 and found that the total 27 years’ X-ray activity of GRS 1915+105 is consistent with this four-branch classification.

Speaker: Nobuyuki Kawai (RIKEN)

2503_GRS1915-Swift20poster.pdf

14:29 Methods to enhance the effective range of UVOT image and spectral data and their applications

A new method (PSF method) for measuring photometries of moderately saturated UVOT sources has been proposed, which increases the dynamic range of UVOT. The brightest UV/optical flash was discovered in GRB 2201101A with the PSF method. Considering the very rapid brightening stage, the scenario of a refresh shock is adopted to explain the optical flash. In addition, we proposed a method (clean extraction) to remove the second-order contamination from UVOT UV grism spectra, increasing the effective wavelength range to about 4000 angstroms. A catalog is being constructed to reveal the temporal and spectral behavior of GRBs at the early stage with the clean extraction, the PSF method and simultaneous X-ray observations. Some preliminary results will be shown.

Speaker: Hao Zhou (Purple Mountain Observatory，Chinese Academy of Sciences)

Poster_swift20_HaoZhou.pdf

14:29 Modelling gamma-ray burst X-ray afterglow spectra with time-evolving photoionisation

Long gamma-ray bursts are produced by the collapse of a massive star at the end of its life. Typically, LGRB spectra are found to be absorbed by a significant amount of gas within their host galaxy. We can estimate the amount of this gas through broadband spectroscopy. X-ray spectra provide the most complete estimate as they probe the total amount of material along the line of sight compared to optical spectra, which can only probe the relatively neutral gas and miss dust contribution. When optical and X-ray inferred column densities have been compared for the same GRB, they typically differ by up to an order of magnitude. This is referred to as the missing gas problem since it is expected to arise from a column of very highly ionised material near the GRB. We fit a flux-selected sample of seven GRB X-ray spectra using a newly developed time-dependent ionised absorber to model the GRB photoionised medium. We find that the time-dependent ionised absorber fits improve upon a standard neutral absorber model fit for six out of seven bursts in our sample, providing evidence for the presence of the missing highly ionised gas. Furthermore, for all six of these, the corresponding best-fit parameters predict a region of size ~ 10 pc with typical number densities of ~ 10$^3$ cm$^{-3}$, consistent with the expected properties of a star-forming region-like environment.

Speaker: Dr Aishwarya Linesh Thakur (Istituto Nazionale di Astrofisica (INAF))

Thakur_poster_Swift20.pdf

14:29 New tools for improved UVOT photometry

The Swift UVOT plays a crucial role in time-domain astronomy, but light curves, especially in the UV, are plagued with "dropouts," outliers with photometric fluxes that are up to 30% lower than surrounding points. These dropouts are caused by localized sensitivity variations in the detector. We have developed algorithms that map out the detector plane and flag these points, producing more reliable photometry at the cost of losing 10-20% of the data. We will demonstrate this process with the AGN in which this problem and solution was first discovered, NGC 5548.

The next step will be to flux correct instead of censoring these data, using more detailed detector sensitivity maps based on millions of measurements in archival data. We are also developing tools to recover the UVOT data affected by the 2023-24 pointing stability anomaly. Our goal is to improve the availability and usefulness of existing UVOT data and the reliability of future observations. This talk will give a preview of these tools and describe the status of their development.

Speaker: Jonathan Gelbord (Spectral Sciences, Inc.)

Gelbord_Jonathan_poster_v2.pdf

14:29 Novae as Exemplars of Physical Processes Encountered in Transients

Classical novae begin as explosive, but not destructive, mass ejection events following a thermonuclear runaway on a mass accreting white dwarf but the "main event" is the subsequent development of the ejecte mass. To understand the photometric and spectroscopic histories of the events requires dealing with physical processes encountered in a broad variety of cosmic transients. The symbiotic-like recurrent novae, such as RS Oph and T CrB, present analogs to the acceleration shocks in supernova remnants. The recombination and re-ionization waves provoked by both sudden and slow brightness variations of the illuminating central white dwarf in the short period nova systems are also seen in TDEs, red novae, ILOTs,and LBVs. Dust formation in the expanding ejecta, a not infrequent event in novae, is also observed in supernovae and a broad range of outflows. Ejecta geometries affect emitted spectra and lightcurves. Large amplitude photometric fluctuations, often interpreted as shocks, can also arise from variations in the luminosity and effective temperature of the remnant white dwarf by being reprocessed in the expanding ejecta. The ejecta structure, inhomogeneous chemically and in density and strongly density and velocity stratified, present an essential exemplay for the study of all transients. In all of these cases, Swift continues to be a unique, invaluable source of multiwavelength data from the UVOT filter photometry and grism spectroscopy and the XRT for the view of the state of the degenerate. We will show examples of how the analysis combines these to tease out the physical picture.

Speaker: Prof. Steven N. Shore (Univ. of Pisa; INAF-OATS)

14:29 Observations of Hot Stars and Interstellar Dust with Swift/UVOT

We review the contributions of Swift/UVOT to our understanding of interstellar dust and hot stars and young stellar populations in both the Milky Way and other galaxies. These two research areas are closely intertwined: UV-bright objects can only be fully understood when the effects of foreground dust are accounted for, yet those same effects can only be studied by observing the properties of UV-bright sources. UVOT is particularly well-suited to investigate variations in the UV dust attenuation law due to the uvm2 filter that is centered on the 2175 Angstrom “bump” feature and its ability to resolve nearby stellar populations. When combined with optical and infrared imaging, UVOT provides powerful constraints on the variability of the extinction law, both across different galaxies and within individual galaxies, in addition to providing key insights into the properties of young stellar populations. UVOT surveys have spanned the Milky Way, Local Group galaxies, the Local Volume Legacy Survey (LVLS), and two multiwavelength deep fields. These surveys are contributing to the most detailed data to date on the UV dust attenuation law and connecting variations in dust attenuation to underlying physical processes and improve our understanding of the UV characteristics of hot stars and young stellar populations.

Speaker: Caryl Gronwall (Pennsylvania State University)

swift20_gronwall.pdf

14:29 PanRadio GRB: An automated triggering program for Swift GRBs with ATCA

To date, radio studies of GRB afterglows have been triggered because of their multiwavelength properties i.e. high energetics or optical brightness. This has left us with a biased image of the radio properties of GRB afterglows and very little information on their earlier time behaviour. In this talk, I will provide an update on the PanRadio GRB program that has been we have been running on the Australian Telescope Compact Array since 2023. I will present an overview of the results from this program from a statistical perspective as well as highlighting to important aspects of the program: (1) a radio detection just minutes post-burst and (2) the ability to perform the long term (> year long) monitoring afterglows allowing for full afterglow characterisation. Our program demonstrates the importance of immediate, precise localisation of GRBs that Swift provides. Starting next year, we will do with the VLA what we’ve been doing with ATCA, but with better sensitivity.

Speaker: Lauren Rhodes (McGill)

Rhodes_Swift20_poster.pdf

14:29 Photo-hadronic pair creation and neutrino production in magnetospheric current sheets of accreting black holes

Non-jetted AGN exhibit hard X-ray emission with a power law spectrum above $\sim$2 keV, which is thought to be produced through Comptonization of soft photons by electrons and positrons (pairs) in the vicinity of the black hole. The origin and composition of this plasma source, known as the corona, is a matter open for debate.
Our study focuses on the role of relativistic protons accelerated in black-hole magnetospheric current sheets in the pair enrichment and neutrino production of AGN coronae. We present a model that has two free parameters, namely the proton plasma magnetization $\sigma_{\rm p}$, which controls the peak energy of the neutrino spectrum, and the Eddington ratio $\lambda_{\rm Edd}$ (defined as the ratio between X-ray luminosity $L_{\rm X}$ and Eddington luminosity $L_{\rm Edd}$), which controls the amount of energy transferred to secondary particles.
Our results indicate a strong dependence of the secondary pair density on the Eddington ratio. More specifically, when $\lambda_{\rm Edd}$ exceeds a critical value $\lambda_{\rm Edd, crit} \propto \sigma_{\rm p}^{-1}$, in which photohadronic interactions in the magnetospheric region can produce enough secondary pairs to create coronae with Thomson optical depths, $\tau \sim 0.10 - 10$. We also present the predicted high-energy neutrino spectrum and discuss our results in light of the recent IceCube observations of TeV neutrinos from NGC 1068, NGC 4151 and CGCG 420-015.

Speaker: Despina Karavola (University of Athens)

Karavola_poster_Swift20.pdf

14:29 Post-EXTraS discovery of a new candidate magnetar in the LMC

The Exploring the X-ray Transient and variable Sky (EXTraS) project represents the most thorough living search for new X-ray pulsators in the XMM-Newton archive, having led to the discovery of about 60 new pulsators and still counting. In 2022, we discovered an X-ray pulsator on the outskirts of the Large Magellanic Cloud (LMC). The source (J0456 from now on) shows a coherent signal with a period of $P\sim7.25\,\mathrm{s}$, which allows us to classify J0456 as a spinning neutron star, a scenario also supported by spectral analysis. Furthermore, J0456 is a highly variable source, with only one detection out of five XMM-Newton and eROSITA observations. In this talk, I will report the results of our Swift monitoring programme and show that, regardless of its classification, this new pulsar represents a peculiar object. The only optical object within the XMM-Newton uncertainty region is a low-mass star. Should the star be the optical counterpart of J0456, this system would be the first of its kind in the LMC and a real puzzle for the current evolutionary models. Alternatively, the object is unrelated, and J0456 is isolated. In this case, the combination of high pulsed fraction ($\sim86\%$) and low luminosity ($\sim2.7\times10^{34}\,\mathrm{erg}\,\mathrm{s}^{-1}$ in the 0.3-10 keV band) suggests that J0456 is a candidate magnetar, the third known outside our Galaxy.

Speaker: Matteo Imbrogno (Istituto Nazionale di Astrofisica (INAF))

Imbrogno_Matteo.pdf

14:29 Precursors from Compact Binary Mergers

A subclass of hybrid Gamma-ray bursts (GRBs) with long duration and peculiar spectral and timing properties was discovered to be related with compact binary mergers. Their main prompt gamma-ray phase is preceded by a fainter and spectrally softer pulse that we interpret as a precursor, possibly produced by a different physical mechanism.
I present the results from the analysis of the brightest GRBs associated with compact binary mergers (GRB 211211A and GRB 230307A) and compare them with leading models for precursor emission, which occurs either before or immediately after the merger.
I show that the high luminosity of some precursors (>1e49 erg/s) poses a challenge to most models proposed to explain their origin.
Ultimately, their nature can only be unraveled using joint gamma-ray/gravitational wave detections. I briefly discuss how multi-messenger constraints would help narrow down the range of models for precursors emission and place meaningful constraints to the NS equation of state.

Speaker: Simone Dichiara (Penn State)

Dichiara_Simone.pdf

14:29 Probing super-Eddington accretion in BeXRBs: Insights from accretion column spectra and CRSF evolution

Be X-ray binaries (BeXRBs) are highly variable systems that host the majority of X-ray pulsars (XRPs). In these systems, accreting material is transferred via the magnetic field lines of the Neutron Star (NS) and concentrated into an accretion column (AC) near its magnetic poles. The AC dynamics suggest a presence of sub-critical and super-critical regimes in which the luminosity and the spectral distribution are highly affected. Moreover, the most luminous outbursts of BeXRBs are known to break through the Eddington limit, and offer our nearest window onto Super-Eddington (SE) accretion. The Becker & Wolff (2007) model (BW07) has successfully reproduced XRP spectra in the super-critical regime, particularly for luminosities in the range of 10$^{37}$−10$^{38}$erg s$^{-1}$. However, its application to SE sources remains limited.

In this work, we apply the BW07 model to BeXRB spectra with luminosities exceeding 10$^{38}$ erg s$^{-1}$. Our analysis begins with a parametric study of the BW07 radiative model to identify self-consistent solutions that conserve energy. We then present best-fit results for the observed X-ray spectra of these systems during their major outbursts. Importantly, all these sources exhibit cyclotron resonant scattering features (CRSF), which provide a direct measure of the NS surface magnetic field strength. In our study, we take into account the characteristic height of CRSF formation and examine degeneracy induced by model assumptions.

For systems with multiple observations across varying luminosity states, we explore the evolutionary track of model parameters, offering insight into the transitions between sub-critical and super-critical regimes, with application to Swift/XRT energy bands.

Speaker: Marios Kouzis (National and Kapodistrian University of Athens)

Poster_Swift20years.pdf

14:29 Probing the progenitors of GRBs with high resolution X-ray spectroscopy: foward NewAthena

Absorption spectroscopy provides precious information on the environment embedding the GRB, as demonstrated by optical and infrared observations of their host galaxies. The next challenging step is to reach the close region (few parsecs), that carries the direct imprints of the progenitor. However at such distances the medium is highly ionized to the extent that only X-ray measurement can probe it effectively. Furthermore, the strong and variable photoinization front produced by the GRB must be properly modelled, as we did with our TEPID code. In this talk I will focus on the powerful diagnostics provided by the numerous X-ray narrow absorption lines expected to populate the spectrum, and discuss the prospects of observation with XRISM and NewAthena. NewAthena, in particular, will allow to measure lines from several ions from the closest to most distant GRBs, opening the possibility to identify popIII vs popII environments in high-z GRBs.
If time allows I will also discuss the prospects of detecting X-ray imprints, including line emission, from the kilonova of NS mergers both on short and long time scales.

Speaker: Luigi Piro (Istituto Nazionale di Astrofisica (INAF))

14:29 Prompt emission in the soft X-rays

The prompt emission of Gamma-Ray Bursts (GRBs) has traditionally been studied in the gamma-ray energy domain (ranging from a 10 keV to ~10 MeV). However, observations in this regime have revealed inconsistencies with standard non-thermal emission models, suggesting the need for a broader investigation across different energy bands. The Swift/XRT, with its rapid on-board follow-up capabilities, has made it possible to capture the prompt emission phase in the soft X-ray domain (0.3–10 keV), thus covering a critical gap in our understanding of GRB emission mechanism.
In the last 20 years, approximately 200 GRBs have been observed in the soft X-ray band during their prompt emission phase, with 50 of these events coinciding with the brightest MeV pulses. This unique dataset has allowed for the systematic extension of prompt emission spectra into the soft X-ray regime, uncovering key spectral features such as low-energy spectral hardening (breaks). These features are fundamental in refining our theoretical models of GRB prompt emission.
In this work, I present a comprehensive study of GRBs observed by Swift/XRT during their prompt emission phase. I will also discuss the implications of these findings for our understanding of the prompt emission mechanism.

Speaker: Samanta Macera (Gran Sasso Science Institute)

14:29 Quasi simultaneous radio/X-ray observations of the newly discovered accreting millisecond X-ray pulsar SRGA J144459.2-604207

SRGA J144459.2-604207 is a newly discovered X-ray binary transient. First detected by the SRG/ Mikhail Pavlinsky ART-XC telescope on February 21, 2024, the X-ray detection was then confirmed by the MAXI instrument on-board of the ISS. NICER data taken on February 21 evidenced the presence of an X-ray pulsation at approximately 447.8 Hz and of type-I X-ray bursts, establishing that SRGA J144459.2-604207 is an accreting millisecond pulsar. Observations at different wavelengths have been carried out searching for counterparts.
As a part of X-KAT, a large MeerKAT open time programme to observe X-ray binaries in the radio band in coordination with large X-ray and optical monitoring programmes, we initiated a radio follow-up of SRGA J144459.2-604207. We also observed SRGA J144459.2-604207 in the X-ray with the Neih Gerels Swift Observatory (Swift), as a part of the SwiftKAT programme, which provides quasi-simultaneous X-ray coverage of the target. The source was detected with XRT on February 22, exhibiting a clear type-I X-ray burst. Radio monitoring consisted of weekly observations conducted from February 22 to March 16, 2024. While SRGA J144459.2-604207 was not detected, we managed to constrain its radio emission. We placed our results in the X-ray vs radio luminosity plane, showing that SRGA J144459.2-604207 is the accreting millisecond pulsar with the lowest radio flux to date.

Speaker: Isabella Mariani (Istituto Nazionale di Astrofisica (INAF))

Swift20_Poster_Mariani.pdf

14:29 Recent developments of the JED-SAD paradigm, a unified accretion ejection paradigm for X-ray binaries :

The hysteresis behavior of X-ray binaries during their outbursts remains a mystery. In this work, we developed a paradigm where the disk material accretes in two possible, mutually exclusive, ways (Ferreira et al. 2006). In the usual alpha-disk mode (SAD, Shakura & Sunayev 73), the dominant local torque is due to a radial transport of the disk angular momentum. In the jet-emitting disk mode (JED), magnetically-driven jets carry away mass, energy, and all the angular momentum vertically. We developed a two-temperature plasma code that computes the thermal balance at each radius for different values of the disk accretion rate (mdot) and transition radius (jJ) between the JED and the SAD (Marcel+18a, A&A 615, A57). This framework has been applied with success to X-rays outburst of GX 339-4 (Marcel et al., 2019, A&A 626, A115) and MAXI J1820+070 (Marino et al. 2021, A&A 656, A63), using data from RXTE, Swift-XRT and BAT, Nicer and NuSTAR. Recently it has also been applied to Cyg X-1 and Swift 1727-1613 where switf-BAT data are very constraining. Combined with the general-relativistic radiative transfer code MONK (Zhang et al. 2019), we are now able to compute polarimetric signatures and compare to IXPE observations. I will introduce the model and present the most recent developments and results.

Speaker: Dr pierre-olivier petrucci (Institute of Planetary science and Astrophysics of Grenoble)

petrucci_pierre-olivier_1.pdf

14:29 SN2022ffg: an interacting Type II SN with a unique plateau in the Swift NUV light curves

Supernovae exhibiting circumstellar matter (CSM) interactions and dynamic signatures provide critical insights into the mass-loss histories of massive stars. SN2022ffg, a Type II supernova observed shortly after the explosion, displayed flash-ionized emission lines of H, He, N, and C lasting for over a week, indicating interaction with a dense nearby CSM. The supernova’s Swift-UV light curve peaked within 5 days, subsequently settling into a rare 20-day plateau, which has never been seen in Type II SNe, while its bolometric light curve remained notably steady over 30 days. Spectroscopic and polarimetric observations reveal a complex, asymmetric CSM structure surrounding the progenitor, with an inner dense CSM and outer shell-like CSM indicated by boxy line profiles during the photospheric phase. Light curve modeling across UV-optical-NIR wavelengths suggests a mass-loss rate of approximately 0.01 Msolar per year and an explosion energy exceeding 2 foe. These observations support the growing understanding that asphericity, often resulting from complex mass-loss processes in massive stars, is a common feature in their CSM environments rather than an exception.

Speaker: Avinash Singh (Stockholm University, Sweden)

2022ffg___Swift_20_Years___Poster.pdf

14:29 Superoutbursts of WZ Sge-type dwarf novae as seen by Swift

WZ Sge-type stars are an extreme subgroup of the dwarf nova class of cataclysmic variables. In contrast to ordinary SU UMa-type dwarf novae, the WZ Sge-type stars exhibit only very rare (approximately once a decade) and long superoutbursts (a few weeks) with amplitudes exceeding 6 mag, and no normal outbursts. A unique property of superoutbursts is the appearance of superhumps, low-amplitude modulations with a period of a few percent longer than the orbital one. The superhumps are explained by a tidal instability of the accretion disc, which grows when the disc expands beyond the 3:1 resonance radius. This causes the disc to become quasi-elliptical and precess. Though X-ray properties of different dwarf novae are not always consistent, on the whole, they can be characterized by suppression of the X-ray flux during an outburst, accompanied by the softening of the X-ray spectrum. In contrast, the WZ Sge-type objects show an increase of their X-ray luminosity during an outburst. Unfortunately, not too many WZ Sge-type dwarf novae have been observed in X-rays, and until recently, only a few of them have complete coverage of an X-ray light curve throughout a superoutburst.

I will present the results of X-ray observations of these objects with Swift/XRT through their superoutbursts and the following decline, and compare the X-ray light curves with optical observations. One of our major results is the discovery of a temporal coincidence of changes in X-ray and superhump behaviour in some of these systems, thus linking the properties of the BL with the outer disc. Also, the post-outburst decline of the X-ray flux in some objects lasted at least a few hundred days, which poses a severe challenge to the disc instability model (DIM).

Speaker: Dr Vitaly Neustroev (University of Oulu)

neustroev_vitaly.pdf

14:29 SVOM/ECLAIRs Gamma-Ray Burst Trigger In-Flight Commissioning

The French-Chinese SVOM satellite (Space Variable Objects Monitor) was launched on June 22, 2024, from the Xichang launch site in China. The mission's objectives focus on detecting and studying astrophysical transient events, with a primary emphasis on Gamma-Ray Bursts (GRBs). The GRB Trigger of the ECLAIRs instrument onboard SVOM has already detected several notable bursts and initiated autonomous satellite slews to enable follow-up observations by the MXT and VT instruments onboard. Additionally, it transmits real-time burst alerts via the SVOM VHF network, enabling follow-up campaigns by the broader scientific community, including several space and ground-based facilities, among which Swift is a key partner.

This presentation provides a status update on the ECLAIRs GRB Trigger following the recent completion of the in-flight commissioning phase. It emphasizes the complementarity between the Count-Rate Trigger and the Image Trigger algorithms, running both in parallel, and details some of the configuration adjustments made in response to real in-flight data. Coupled with the very good performances of the ECLAIRs detector plane and onboard processing unit, the Trigger has enabled SVOM to detect and localize accurately several notable GRBs, including X-ray rich GRBs and GRBs with redshift determinations, as reported in GCN circulars already from the early stages of commissioning.

Speaker: Stephane Schanne (CEA Paris-Saclay/IRFU)

stephane_schanne_1_SvomEclairsTriggerCommissioning.pdf

14:29 SVOM: Observatory Science

Launched on June 22, 2024, the SVOM satellite extends its mission beyond gamma-ray burst (GRB) science, exploring a wide range of high-energy phenomena and transient astrophysical sources. This presentation highlights SVOM's activities on the Observatory Science related to non-GRB sources. We will showcase the architecture and functionality of the quick-look analysis pipeline for ECLAIRs X-band data (4–150 keV) and present early findings from high-energy sky monitoring with ECLAIRs. Notable results include detailed monitoring of the blazar 1ES 1959+650 and observations of spectral state transitions in X-ray binaries during SVOM’s initial months of operation. These first observations demonstrate SVOM’s potential to deepen our understanding of the dynamic high-energy universe.

Speaker: Sébastien LE STUM (APC, France)

Poster_SwiftConf_SvomObsSc_v2.pdf

14:29 Swift and AGILE: a successful synergy

The beginning of the 21st Century saw the advent of two satellites that revolutionised the high-energy astrophysics. The AGILE satellite, for the first time, used a Silicon pair conversion detector for gamma-ray detection, allowing for a leap forward with respect to previous spark chamber technology. The Swift satellite combined optical, UV and X-ray telescopes with an unprecedented repointing capabilities. These allowed us to investigate flaring celestial sources right in time and simultaneously from optical up to GeV energy bands.
In this contribution we describe the scientific observations of different classes of sources, from GRBs to AGNs and Galactic sources, which not only benefited from Swift observations but for which Swift demonstrated its pivotal and unique contribution.

Speaker: Dr Stefano Vercellone (Istituto Nazionale di Astrofisica (INAF))

Vercellone_AGILE.pdf

14:29 Swift and multi-wavelength monitoring of the early rise of the black hole X-ray binary, Swift J1753.5-0127

Despite decades of research, predicting outbursts of X-ray transients, and witnessing their beginning stages, remains very challenging. The cause of these X-ray brightenings is thought to be the sudden increase of accretion of matter onto a black hole or neutron star, initiated by the ionization of hydrogen in the accretion disc. I present recent observational advances in our understanding of how X-ray transients first brighten, focussing on the best case, optical and X-ray monitoring of the early rise of the black hole X-ray binary, Swift J1753.5-0127 in 2023. After an initial optical detection from ground-based telescopes, Swift is used to constrain the UV (with UVOT) and X-ray (with XRT) delay of the outburst rise. A delay of ~4 days is measured between a thermal instability developing in the accretion disc, causing heating fronts to begin propagating through the disc (seen by an optical brightening, then UV), and the onset of accretion onto the black hole (X-ray brightening). We witness the propagation of the heating wave, as a steady increase in the flux and surface area of the disc, and we constrain the disc viscosity. I demonstrate the ability of optical monitoring, along with rapid X-ray and UV follow-up with Swift, to be able to constrain disc instability models for X-ray transients.

Speaker: Dave Russell (New York University Abu Dhabi)

SwiftJ1753-Swift-Florence-poster.pptx

14:29 Swift monitoring reveals transient ULXs in NGC4559

The Swift satellite, thanks to its fast slew capability, has provided the opportunity to monitor extragalactic X-ray transients with a high cadence. This has been especially crucial in understanding that Ultra-luminous X-ray Sources (ULXs) exhibit long-term variability, the origin of which remains unclear.

In this talk, I will present the analysis of a poorly studied region of the galaxy NGC 4559. By cross-matching Swift/XRT data with Chandra images, we identified that this region contains four ULXs which have different long-term characteristics, in terms of light-curve behaviour in the broad band as well as in the hard and soft energy ranges.

Speaker: Elena Ambrosi (Istituto Nazionale di Astrofisica (INAF))

14:29 Swift’s Role in Shaping MAGIC’s Multi-Wavelength high energy Astrophysics

The MAGIC telescopes, designed to observe gamma rays at energies exceeding 50 GeV, have significantly advanced their scientific capabilities through multi-wavelength (MWL) campaigns involving the Neil Gehrels Swift Observatory. Beginning operations just two years after Swift, the young MAGIC collaboration rapidly embraced MWL campaigns, integrating Swift's X-ray and UV observations with TeV gamma-ray data. This collaboration enabled the detection of flaring states in active galactic nuclei (e.g., 3C 279, TXS 0506+056, TON 599, and BL Lac), the long-term monitoring of blazars and the construction of broad spectral energy distributions (SEDs) that have advanced our understanding on the physical processes in these sources. Swift's observations were also critical in interpreting the TeV emission detected in GRB 190114C, a landmark discovery in high-energy astrophysics. This partnership has not only enriched MAGIC’s science but has also had a transformative impact on the collaboration, enabling it to fully exploit the potential of joint MWL campaigns.

Speaker: Jahanvi Jahanvi (Università degli Studi di Udine)

jahanvi_jahanvi.pdf

14:29 T Corona Borealis Will Be the Brightest Classical or Recurrent Nova Ever Observed in X-rays

Classical and Recurrent novae occur on the white dwarf component of a close, or not so close, binary system. They participate in the cycle of Galactic chemical evolution in which grains and metal enriched gas in their ejecta are a source of heavy elements for the ISM. Once in the diffuse gas, this material is ultimately incorporated into new regions of star formation. We have continued our hydrodynamic studies by following accretion onto 1.35Msun white dwarfs in order to predict the upcoming explosion of T Corona Borealis (TCRB). TCRB contains a massive, 1.35M$_\odot$, white dwarf orbiting a red giant (M3-M4 III) with a 227 day period. It has been observed to explode approximately every 80 years. We do not know the composition of the underlying white dwarf in this system and, therefore, have evolved both carbon-oxygen and oxygen-neon white dwarfs through a thermonuclear runaway and return to quiescence. We have found that (1) such a system ejects sufficient $^7$Li that, over its total lifetime as a Recurrent Nova it can eject as much $^7$Li as a Classical Nova; (2) It is ejecting far less mass than accreted and so the white dwarf is growing toward the Chandrasekhar Limit and will explode as either a SN Ia or experience accretion induced collapse; (3) we have followed the evolution of just the white dwarf after the escaping matter has been removed from the simulation and find that days to weeks after the initial outburst the radiating white dwarf will reach luminosities exceeding $10^5$ L$_\odot$ and temperatures exceeding $2\times10^6$ K. Thus, TCRB, which is at a distance less than a kpc will become, for a short time, the brightest nova ever to be observed in X-rays. T CrB is an excellent candidate for a detailed Swift investigation.

Speaker: Prof. Charles E. Woodward (University of Minnesota)

SWIFT20-CEW-Poster-49.pdf

14:29 TeV afterglow emission from a multi-component GRB jet using the kinetic approach

Recent years have seen a growing sample of TeV emission detections in gamma-ray burst afterglows, as well as an increasing role for structured jets in afterglow modelling. Using a kinetic approach, with adiabatic expansion and fully self-consistent IC scattering, we show that the structure of an afterglow jet impacts its TeV emission, with jets where the energy falls off more sharply with angle showing a decrease in Inverse Compton (IC) peak flux relative to synchrotron peak flux at the cooling break.
We compare our results to the semi-analytical code afterglowpy, finding a good agreement with our model across the broadband spectrum except at early times off axis where the effects of baryon loading are important. By using the best fit parameters provided by afterglowpy, we are also able to reproduce the light curves of GRB 170817A in our model.
From comparing electron cooling in the cases where there is no IC cooling, Thomson cooling and an inclusion of Klein-Nishina effects, we find that the synchrotron spectra can only be distinguished in the X-ray band if the Compton potential is significantly increased. The smooth and gradual transition of the self-consistent KN cooling also leads to a disparity in the cooling between our results and semi-analytical solutions based on asymptotic limits.
Finally, we consider the impact of features such as the reverse shock on the forward shock TeV emission using our kinetic approach.

Speaker: John Hope (University of Bath)

Hope_John_1.pdf

14:29 The ASTRI Mini-Array at the time of multi-messenger astronomy

The ASTRI Mini–Array is currently being installed in Tenerife at the Observatorio del Teide to explore the gamma-ray sky in the 1-100 TeV energy range with unmatched angular resolution (a few arcminutes) across a wide field of view (10.5 deg). The array consists of nine IACTs (Imaging Atmospheric Cherenkov Telescopes), each equipped with a 4-meter diameter dual-mirror system featuring a Schwarzschild-Couder-like optical configuration, functioning as an aplanatic system, and an innovative compact camera that utilizes SiPM (Silicon PhotoMultipliers) sensors. This contribution briefly overviews the ASTRI Mini–Array project’s layout, capabilities, and scientific objectives. The ASTRI Mini-Array can play an important role in multi-messenger astronomy to better understand galactic and extragalactic astrophysical aspects, combining the information inferred by other observational facilities. In this respect, a parallel observation program with ASTRI Mini-Array and Swift already started.

Speaker: Dr Stefano Vercellone (Istituto Nazionale di Astrofisica (INAF))

Vercellone_ASTRI.pdf

14:29 The Growing Population of Radio-Dectected Merger Driven GRBs: Their Environments, Jets, and Afterglows

The launch of Swift revolutionized our understanding of merger driven/short duration GRBs, with the first broadband afterglow being detected shortly into Swift's life. The detection of an afterglow is imperative for understanding the burst's properties, with the radio band in particular providing key insight into the collimation and environment of the GRB. Despite the importance of the radio afterglow, the first decade of Swift's life resulted in only 5 radio-detected short GRBs, compared to over 70 short GRBs with X-ray detections. Thanks to the improved sensitivity of radio facilities and our recent campaign to probe a large sample of short GRBs in previously unexplored temporal regimes, we have more than tripled the number of detected radio afterglows in the second decade of Swift's life. In this talk, I will demonstrate how these radio detections, in conjunction with X-ray and optical afterglows from Swift and other observatories, reveal a diverse population of GRBs, with a focus on GRBs with non-standard radio afterglows. I will additionally take a holistic look at the properties of the radio detected population to determine how their afterglows, environments, and jets differ from the overall merger driven GRB population. I will conclude with how we can utilize the X-ray afterglow to inform our radio observations in order to increase the chance of detection.

Speaker: Dr Genevieve Schroeder (Cornell University)

14:29 The highs and lows of Be/X-ray transients unveiled by Swift

I will present the results of our ongoing Swift monitoring of Be/X-ray transients that we started almost ten years ago. We have followed up more than ten galactic systems (i.e., GRO J1008-57, SAX J2103.5+4545, GX 304-1, GRO J1750-27, KS 1947+300) during and after their outbursts. The aim of our monitoring campaigns was to study the process of low-level accretion onto magnetized (10^12-10^13 G) neutron stars, and to determine if neutron-star crust cooling emission could be detected, similar to what was seen for the weak-field accreting neutron stars. What we have found is that these sources show a wide variety of behaviors when they transit to quiescence after their outburst activities: some sources directly transit to quiescence (e.g., GRO J1750-27), others decrease slowly in time (e.g., SAX J2103.5+4545), some of them stay in an intermediate level of 10^34-10^35 erg/s (e.g., GRO J1008-57, GX 304-1), others also show a reflaring activity before turning to quiescence (e.g., KS 1947+300), and one of them show a recurrent decaying low X-ray luminosity (4U 0115+63). We will show our results of the monitoring campaigns and introduce the physics behind these variable behaviors at low X-ray luminosities.

Speaker: Alicia Rouco Escorial (European Space Agency)

RoucoEscorial_Alicia.pdf

14:29 The INTEGRAL/IBIS and Swift/XRT long-lasting partnership

The last 20 years have been studded with a wealth of unexpected results in high-energy astrophysics, as typified by discoveries made by Swift, INTEGRAL, and other high-energy observatories. Here we would like to highlight the major role played by Swift/XRT in supporting the INTEGRAL mission in consolidating new findings, allowing a better classification/characterisation of unknown sources, thanks to its few arcseconds source location accuracy, and studying known ones, thus paving the way to a better knowledge of the sky above 10 keV.

This has largely been due to the collaborative effort of the research teams involved in the two projects, but also to the foresight of Neil Gehrels, who before being the Swift PI, was mission scientist of INTEGRAL and thus the trade union for this successful collaboration. From source identification to broad-band spectral studies, from variability searches to source population analysis, XRT has always provided an extra element of understanding in the intricate path that has allowed a better knowledge of the INTEGRAL sky.

Few case studies, some overall statistics and future prospects will be presented to describe this 20-year-long journey.

Speaker: Angela Malizia (Istituto Nazionale di Astrofisica (INAF))

Landi_Raffaella.pdf

14:29 THE NATURE OF EXTRAGALACTIC UNIDENTIFIED GAMMA-RAY SOURCES (UGS): THE KEY ROLE OF SWIFT/XRT

Over the past decade, the Swift satellite carried out a dedicated observational campaign targeting unassociated gamma-ray sources (UGSs), which constitute ~30% of the gamma-ray detections reported by the Fermi satellite. UGSs are of significant interest in high-energy astrophysics, potentially hiding new unidentified blazars, the most numerous class of extragalactic gamma-ray sources and possible neutrino emitters, or other types of AGNs. To unveil the nature of these sources, we performed a multiwavelength analysis using all available Swift/XRT images covering the error box region of ~750 UGSs, in order to identify their lower energy counterparts. We used ~160 hours of optical observations with 8-10m class telescopes to classify the UGS optical spectroscopic counterparts.
From the analysis of their spectral properties we determine the redshift or establish stringent lower limits. This comprehensive study enables the classification of UGSs, as well as the construction and characterization of their broadband spectral energy distributions (SEDs), particularly in the X-ray band. These results allow to address important scientific questions such as the blazar demographics and evolution, the mechanisms underlying photon and neutrino production, and the identification of possible gamma-ray non-blazar sources (like quasars and Seyferts) as well as promising candidates for TeV gamma-ray emission.

Speaker: Boris Sbarufatti (Istituto Nazionale di Astrofisica (INAF))

Sbarufatti_Boris.pdf

14:29 The nuclear transient AT2017gge: a tidal disruption event in a dusty and gas-rich environment

The tidal forces from SMBHs can disrupt stars in their vicinity. These tidal disruption events (TDEs) manifest themselves as a luminous, short-lived, flares coming from the nuclei of otherwise quiescent galaxies and represent an important tool to study the properties of dormant SMBHs. They are exquisite multi-wavelength sources, as they produce very bright flares in different bands of the electromagnetic spectrum, extending from X-rays to radio wavelengths, with the prompt emission usually peaking in the UV/optical and/or in soft X-rays.

The first TDE candidates were discovered in the X-rays band and thanks to the increasing survey power in the time domain astronomy the population of observed TDEs has quickly grown. Now they represent a class of optical nuclear transients with distinct observational features.

However, the origin of the diverse emission properties of TDEs are not fully understood. Three different scenarios have recently been proposed: outflows, emission by shocks from intersecting debris streams and thermal reprocessing of accretion power by a layer of gas. These models are still under discussion and imply different geometries of the emitting region and thus they predict different observing features. Dense multivawelength monitoring campaigns are fundamentals to investigate the underlying TDE emission mechanisms and the advent of Swift satellite represented a major step in the TDE monitoring strategies, finally allowing for systematic and early-started follow-up in the UV and X-rays bands, beside the usual optical monitoring. This resulted in revealing an intriguing and puzzling diversity in the observational properties of the TDE population.

I will present the results from a dense multi-wavelength photometric and spectroscopic follow-up campaign of the TDE AT2017gge. Thanks to a promptly started Swift follow-up, a soft X-ray flare delayed with respect to the optical/UV peak has been detected and it was found to be rapidly followed by a MIR echo and by the emergence of a number of long-lasting high ionization coronal emission lines. Remarkably, a transient high ionization coronal NIR line is also detected. These observations proved for the first time a clear connection between a TDE flare and the appearance of extreme coronal emission lines (ECLEs). The implication on the underlying UV/Optical emission mechanism and on the properties of the emitting region will be accurately discussed.

Speaker: Francesca Onori (Istituto Nazionale di Astrofisica (INAF))

Poster_Onori_AT2017gge.pdf

14:29 The physics behind the emission modes in the transitional millisecond pulsar PSR J1023+0038: insights from IXPE, Swift, VLT and VLA

Transitional millisecond pulsars (tMSPs) bridge the evolutionary gap between accreting neutron stars in low-mass X-ray binaries and millisecond radio pulsars, offering a unique laboratory to study the interplay between accretion and pulsar activity. These systems exhibit a distinctive subluminous X-ray state characterized by alternating high, low and flaring emission modes.
Swift/XRT has always had a key role in identifying mode transitions in the prototype tMSP, PSR J1023+0038. Recent multi-wavelength campaigns (including Swift/XRT) on the source have helped establish a solid understanding of how tMSPs operate and are powered.
More recently, using polarimetric data from the Imaging X-ray Polarimetry Explorer (IXPE), the Very Large Telescope (VLT), and the Karl G. Jansky Very Large Array (VLA), together with mode-monitoring observations from Swift/XRT, we conducted the first multiwavelength polarimetric analysis of PSR J1023+0038.
A linear polarization of (12±3)% in the 2–6 keV band was observed during the high mode. The polarization angle aligns with the optical polarization observed by the VLT, suggesting a shared physical mechanism. During the low mode, the significance was insufficient for detailed analysis, resulting in an upper limit of 26% (90% confidence) on the polarization degree. The results strongly indicate that both optical and X-ray polarization originate from synchrotron radiation at the shock formed by the interaction of the pulsar wind with the inner accretion disc.
Finally, simultaneous radio, optical, and X-ray observations obtained as part of this campaign have, for the first time, shed light on the poorly understood flaring mode emission, emphasizing the critical role of outflows in tMSPs.

Speaker: Maria Cristina Baglio (Istituto Nazionale di Astrofisica (INAF))

poster_swift20_MCB.pdf

14:29 The quest of life-as-we-know-it outside the Solar system: the time-evolution of the ultraviolet habitable zone

The majority of discovered rocky exoplanets in the habitable zone (HZ) orbits around old M-dwarfs, but it is unclear if the high-energy emission of these stars provides a suitable environment for the origin of life. According to Spinelli el al. 2023, the current Near Ultraviolet (NUV) luminosity of M-dwarfs hosting HZ exoplanets is too low to trigger RNA precursors formation on them. By combining Swift-UV/Optical and GALEX data, we investigate the temporal evolution of their ultraviolet habitable zone (UHZ), the annular region around a star in which an exoplanet could experience a suitable ultraviolet environment for the presence and emergence of life, and its intersection with the HZ around K and M stars. I will show the temporal evolution of radial extension of the UHZ and its intersection with the classical HZ for different stellar types, focusing also on the curious case of Proxima Cen.

Speaker: Giancarlo Ghirlanda (INAF - Osservatorio Astronomico di Brera)

Poster_Spinelli.pdf

14:29 The revenant core of ESO511-G030 as monitored by Swift: the linked evolution of the disc/coronae system.

ESO511-G030, a previously bright AGN showing a prominent soft-excess, was observed in both UVs and X-rays in an unprecedented faint flux level in 2019 and no hints of a soft X-ray excess. Since then, we have been monitoring this AGN using Swift (XRT-UVOT) and ground based facilities, finding out that the source, after a few years of quiescence, has been increasing its flux since 2023 and is now back to its formerly known high flux level. The related multi-epoch/multi-wavelength exposures, encompassing optical/UV and X-ray spectra thanks to Swift, represent a unique dataset that enables us to track the evolution of the different emission components (from a photometrical and spectral perspective) during different flux levels (spanning a factor of ~10) of the source.

Speakers: Dr Riccardo Middei (Space Science Data Center (ASI)/ OAR (INAF)), Dr pierre-olivier petrucci (Institute of Planetary science and Astrophysics of Grenoble)

14:29 The role of internal shocks in prompt gamma-ray emission: implications for synchrotron emission

Synchrotron radiation has been for decades the main candidate to explain prompt emission in gamma-ray bursts (GRBs), while shocks have been widely employed as dissipation mechanisms. Although most GRB detectors, such as BAT, are sensitive to energies starting from ~10 keV, the emission in soft X-rays, such as detected by Swift's XRT, and optical wavelengths is also crucial to understand and model the bursts' spectral shapes. From a dissipation perspective, the formation and propagation of internal shocks upon the collision of shells within the relativistic jet of a GRB is a natural byproduct of the jet’s varying speeds. We thus employ a synchrotron model which considers the contributions of both reverse and forward shocks, extending the emission to X-rays and optical wavelengths. We discuss the implications of our model for the current state of observations, the changes brought upon by varying our parameter space, and compare our results to similar approaches where Band-like functions are used to model the prompt emission.

Speaker: Gustavo Soares (Istituto Nazionale di Astrofisica (INAF))

SWIFT_20_POSTER.pdf

14:29 The selection effect in the Epi-Liso correlation of LGRBs

The $E_{\rm p,i}$--$L_{\rm iso}$ correlation of long gamma-ray bursts (LGRBs) has been regarded for a long time as a fundamental correlation for standardizing LGRBs to probe the cosmology and constrain LGRB physics. However, the authenticity of this correlation may be affected by potential selection effects, which are likely overlooked in the current small sample of LGRBs with measured redshift and luminosity. In this conference, I would like to present our recent work of simulating a large LGRB sample that can well reproduce the observed distributions of LGRB parameters to study the selection effects in the $E_{\rm p,i}$--$L_{\rm iso}$ correlation. We first obtain the mock $z$ and $L_{\rm iso}$ from the model of redshift and luminosity distributions in previous work, then yield the spectral parameters: $E_{\rm p,o}$ based on the observed bivariate ($E_{\rm p,i}\{z, E_{\rm p,o}\}$, $L_{\rm iso}$) distribution and $\alpha$ based on the observed bivariate ($\alpha$, $E_{\rm p,o}$) distribution. This allows the mock data for each parameter to perfectly follow the observed distribution. Based on this simulated sample, we find the ($E_{\rm p,i}$, $L_{\rm iso}$) distribution, which will directly affect the best-fitting result of the correlation, is significantly dependent on the value of peak flux $P$. This indicates that the effect of $P$ selection should be sufficiently considered in the study and use of the correlation. Notably, to make the simulated $P$ distribution consistent with the observed distribution, the mock $E_{\rm p,o}$ has to be obtained from the mock $E_{\rm p,i}$ which is simulated based on the observed ($E_{\rm p,i}$, $L_{\rm iso}$) distribution. This means that the ($E_{\rm p,i}$, $L_{\rm iso}$) distribution is still effective to constrain the LGRB parameters.

Speaker: Guangxuan Lan (IRAP/OMP)

LAN_Guangxuan.pdf

14:29 The SVOM/ECLAIRs offline trigger pipeline for the detection of γ/X-ray transients

ECLAIRs, the leading instrument onboard the SVOM mission, is tasked to autonomously search for Gamma-Ray Bursts (GRBs) and other high-energy transients within its wide field of view ( ~2 sr) in the 4-150 keV energy range. To complement the onboard detection capabilities and to take advantage of a better understanding of the instrumental context and huge computing resources, an offline trigger (OFT) pipeline performs blind searches, making use of data as soon as they become available on ground. Targeted searches focusing on multi-wavelength and multi-messenger external inputs will also be integrated into the OFT pipeline.
In this talk, we will present the overall architecture of the OFT pipeline, outlining various methods executed simultaneously to search for high-energy transients, including a detection method based on wavelet decomposition. A Machine Learning based detection method is also under development. First OFT results on in-flight ECLAIRs data will also be presented.

Speaker: Mr Marius Brunet (IRAP)

BRUNET_Marius.pdf

14:29 Time domain astrophysics with transient sources

The timing analysis of transient events (TEs) offers a powerful tool for exploring numerous open questions in modern astrophysics. We have developed the mathematical and physical methods required to estimate delays between two lists of Time of Arrival (ToA) measurements. The HERMES mission, scheduled to launch in March 2025, will deploy a constellation of six nano-satellites in Low Earth Orbit (LEO), each equipped with X-ray and γ-ray detectors covering the energy range of 3 keV to 2 MeV.

By estimating delays in TE observations, the source's position can be determined using triangulation methods. This allows other instruments to point precisely at the extrapolated coordinates. Furthermore, the timing techniques we have developed also provide insights into the variability (e.g., the minimum timescale) of TEs and the periodicity of pulsating signals.

Speaker: Wladimiro Leone (Istituto Nazionale di Astrofisica (INAF))

Leone_Wladimiro.pdf

14:29 Ultraviolet Insights: Distinguishing Type Ia Supernova Subtypes with Two Decades of Swift UV Photometry

In recent decades, distinct subtypes of Type Ia supernovae (SNe Ia) have been discovered that deviate from the canonical luminosity-width relationship. These non-standardizable objects risk contaminating high redshift (z > 0.5) cosmological samples, including those anticipated from the Roman Space Telescope and LSST. While SN Ia subtypes are traditionally determined using peak-light optical spectra, these upcoming surveys will be spectroscopically incomplete, posing a significant challenge to maintaining sample purity. Building on nearly twenty years of Swift observations of 130 SNe Ia in the local universe, we present a novel method for distinguishing SN Ia subtypes using only rest-frame UV photometry. Our method successfully removes all non-standardizable subtypes from our sample. Based on this legacy Swift data, we project that our diagnostic will yield ~90% pure samples of standardizable SNe Ia observed by LSST at redshift z > 0.5 and prove a valuable tool in ensuring the purity of modern cosmological samples of SNe Ia.

Speaker: Grace Showerman (Michigan State University)

Showerman_Grace.pdf

14:29 ULXs long-term evolution: the key role of Swift/XRT

Ultraluminous X-ray sources (ULXs) are an intriguing class of X-ray binaries, most of them observed in nearby galaxies, with luminosity > 10^39 erg/s. Observational evidences favor their interpretation as super-Eddington accretors. Swift/XRT has played a fundamental role in the characterization of ULXs long-term evolution, being the only active X-ray telescope, which allows regular and repeated visits of a source for a long period (e.g. a year). Thanks to Swift/XRT monitorings, it has been possible to discover and study a multiplicity of long-term variability behaviors in ULXs, such as super-orbital periodicities, flaring activity, bimodal flux distribution (e.g. Pintore et al. 2021, Salvaggio et al. 2022) and to discover new transient sources (e.g. Pintore et al. 2018, Robba et al. 2022). I will recap the long-term properties of ULXs, considering both persistent and transient sources, fundamental to understanding these elusive class of objects, focusing on the uniqueness of Swift/XRT for these kind of studies. I will show our results, among which the variability and spectral analysis of the ULXs in NGC925, containing one of the most luminous ULXs known (i.e. L > 10^40 erg/s) and a transient source with a long-term periodicity (Salvaggio et al. 2022).

Speaker: Chiara Salvaggio (Istituto Nazionale di Astrofisica (INAF))

poster_salvaggio_swift20.pdf

14:29 Unraveling the Origins of GRB X-ray Plateaus through a Study of X-ray Flares

The plateau phase observed in the early X-ray light curve of GRBs (lasting up to thousands of seconds) has been a subject of debate since its discovery by the Neil Gehrels Swift Observatory in 2005. First, I will show that the plateau phase can be explained within the classical GRB model by considering a jet Lorentz factor of tens expanding in a wind-type environment. In this model, the end of the plateau marks the beginning of the deceleration phase. Then, I will compare the properties of X-ray flares in bursts both with and without an X-ray plateau. It was found that the distributions of flare properties are similar in each group. Specifically, the peak time of the flares and the ratio of the flare width to the flare peak time which is found to be ~ 1, regardless of the presence of a plateau. I will conclude the talk by discussing these results in view of the different theoretical models explaining the plateau.

Speaker: Hüsne Dereli-Bégué (Bar-Ilan University)

Dereli-Begue_59.pdf

14:29 Unveiling the periodic variability patterns of the X-ray emission from the blazar PG 1553+113

The search for periodicity in the multi-wavelength high variable emission of blazars is a key feature to understand dynamical processes
at work in this class of active galactic nuclei. The blazar PG 1553+113 is an attractive target due to the evidence of periodic oscillations
observed at different wavelengths, with a solid proof of a 2.2-year modulation detected in the γ-ray, UV and optical bands. We aim
at investigating the variability pattern of the PG 1553+113 X-ray emission using a more than 10-years long light curve, in order to
robustly assess the presence or lack of a periodic behavior whose evidence is only marginal so far. We conducted detailed statistical
analyses, studying in particular the variability properties of the X-ray emission of PG 1553+113 by computing the Lomb-Scargle
periodograms, which are suited for the analyses of unevenly sampled time series, and adopting epoch folding techniques. We find out
a modulation pattern in the X-ray light curve of PG 1553+113 with a period of ∼1.4 years, about 35% shorter than the one observed
in the γ-ray domain. Our finding is in agreement with the recent spectro-polarimetric analyses and supports the presence of more
dynamical phenomena simultaneously at work in the central engine of this quasar.

Speaker: Tommaso Aniello (Istituto Nazionale di Astrofisica (INAF))

Aniello_Tommaso.pdf

14:29 Using Swift’s Ultraviolet Lens: Bumps, Colors, and the Weirdest, Most Perplexing, Non-Standardizable Type Ia Supernovae

Over the past decade, the proliferation of sky surveys has enabled the discovery of many Type Ia Supernovae (SNe Ia) promptly after they explode, unveiling new, peculiar phenomena in their first days. In this talk, I will highlight recent discoveries relating to early-time flux excesses, which Swift showed are especially prominent in the UV, discovered for a growing number of SNe Ia. First, I will show that all SNe Ia with non-monotonic rising light curve bumps are either 2003fg-like or 2002es-like, two non-standardizable, peculiar SN Ia subtypes. Second, follow-up Swift photometry reveals that these two subtypes also have distinct UV colors. This allows them to be distinguished from other SNe Ia subtypes, potentially indicating a common origin and other shared characteristics for these peculiar objects. Finally, I will conclude by sharing ongoing work to identify, classify, and
Swiftly follow up on SNe Ia within a day of the explosion at the University of Hawaii’s Institute for Astronomy.

Speaker: Willem Hoogendam (University of Hawaii Institute for Astronomy)

Swift20_Hoogendam_Poster.pdf

14:30 → 15:30 GRB central engines and jets

14:30 Interpreting the 10 MeV emission line in GRB 221009A as high-latitude emission from an annihilating pair bubble

Ever since the early years in the Swift mission, it has been clear that the low-end of the gamma-ray burst (GRB) luminosity distribution has yet to be unveiled, holding the key to the intrinsic rate of GRBs and possibly to their jet structure. Yet, some of the trickiest riddles that GRB astronomy posed to us in the last few years came at the opposite end of the luminosity distribution, where the outrageously bright GRB 221009A shattered the statistics based on several decades of previous GRB observations. Even letting aside the statistics, many properties of this GRB and of its afterglow still lack a convincing explanation. Among these, a bright, narrow spectral frature at around 10 MeV, discovered in Fermi/GBM data around 300 s after the initial precursor, has yet to be fully explained.
In this talk, I will present a scenario that is capable to explain this feature and the apparent temporal evolution of its properties. At the same time, the model explains some puzzling aspects of the TeV afterglow and sheds light on some properties of the progenitor collapsing star.

Speaker: Dr Om Sharan Salafia (Istituto Nazionale di Astrofisica (INAF))

2025_Swift20.pdf

14:45 Orphan Afterglows - AT 2023sva and the State of the Field

There have been hundreds of optical afterglows detected through follow-up observations of well-localized long gamma-ray burst (LGRB) triggers, many made possible by Swift's X-ray Telescope's precise localization capabilities. The advent of state-of-the art time-domain surveys including the Zwicky Transient Facility have also enabled the serendipitous discovery of optical afterglows without an associated GRB trigger. If post-facto searches through GRB archives do not find observed associated gamma-ray emission to these optically-discovered afterglows, they are known as "orphan" afterglows. There have been six examples of orphan afterglows with confirmed redshift measurements in the literature. Determining the physical origin of these events is extremely important, as their studies allow us to probe many open questions in GRB science, including understanding the true rate and angular structure of LGRB jets along with determining how important mass-loading is for successful jets. In this talk, I will give a brief overview of the state of the orphan afterglow field, highlighting major results from different works in the literature. I also will present multi-wavelength (optical from various ground-based facilities, radio from VLA and uGMRT, and X-ray from Swift) analysis of the latest orphan afterglow AT 2023sva, a luminous and radio-loud event that shows evidence for possessing a structured jet. I will end my talk by placing AT 2023sva within the context of the orphan afterglow and LGRB population as a whole.

Speaker: Gokul Srinivasaragavan (University of Maryland College Park)

OrphanAfterglows.pptx

15:00 Flares, energy injection, and decoding broadband GRB afterglows via XRT observations

For the analysis of broadband radio-through-x-ray GRB afterglows, the x-ray observations made via the Niel Gehrels Swift X-ray Telescope (XRT) are a crucial tool. As the x-ray afterglow emission is not typically contaminated by any thermal counterpart (optical and infrared), nor affected by scintillation or self-absorption that can complicate the picture at radio, the post-burst x-ray emission can generally be assumed to purely trace the afterglow. For the short GRB 160821B, a detailed look at the XRT data revealed an episode of energy injection, which in turn allowed the subtraction of the optical afterglow model from the data, revealing the best sampled kilonova observed within the afterglow of a regular short-hard GRB. More recently, the XRT observations of GRB 231117A reveal a flare at ~2 hours post burst – the afterglow to this GRB again requires energy injection, however, unlike GRB 160821B, the required energy results in a violent shock system. Here I will describe how such a violent shock from energy injection can result in the observed x-ray flare and longer wavelength emission consistent with the broadband afterglow. The presence of significant energy injection in short GRBs supports the existence of longer-lived engines or outflow stratification, may hold clues to jet launching and baryon loading processes, and may help in understanding the NS-merger origin for the recent long-engine-duration merger-GRBs 211211A, and 230307A.

Speaker: Gavin Lamb (Liverpool John Moores University)

GPL_SwiftCon.pdf

15:15 Magnetar Evidence in Central Engines of Peculiar Gamma-Ray Bursts

Recent observations of peculiar gamma-ray bursts (GRBs), such as GRB 211211A and GRB 230307A, challenge the traditional view that hyper-accreting black holes power these events. Instead, key signatures—temporal, spectral, and kilonova features—suggest millisecond magnetars as central engines, formed in compact star mergers. This talk highlights recent progress in understanding magnetar-driven GRBs and discusses their implications for GRB progenitors, neutron star physics, and merger energetics.

Speaker: Binbin Zhang (Nanjing University)

15:30 → 16:00 GRB as probes

15:30 GRBs as tracers of star formation and the distant ISM

TBD

Speaker: Dr Patricia Schady (University of Bath)

schadyp_GRBasProbes.pdf

16:00 → 16:30 Coffee break

16:30 → 17:30 GRB as probes

16:30 GRBs as probes of the high-z Universe

The characterization of galaxies at the highest redshifts remains one of the central goals in contemporary astrophysics. For the last two decades, GRBs have been heralded as effective diagnostic to probe the interstellar medium (ISM) of high-redshift faint star-forming galaxies and their metal content. An opportunity to fulfill this promise was provided by the bright GRB 210905A at redshift z=6.3 and by the recent blast of GRB 240218A at redshift z=6.8, both discovered by Neil Gehrels Swift Observatory.

VLT/X-shooter optical spectroscopy of GRB 210905A afterglow allowed to detect and characterize in detail neutral-hydrogen, low-ionization, high- ionization and fine-structure absorption lines, as well as a tentative Lyman-α emission. Metallicity, kinematics, chemical abundance pattern, dust depletion and dust-to-metal mass ratio could be determined for the ISM and CGM of the GRB host galaxy. Additionally, late-time HST and VLT/MUSE observations of the GRB field revealed a complex picture of the GRB host galaxy and its surroundings. Another possibility to study the neutral gas in such galaxies at the end of the reionization era has been recently provided thanks to the VLT/X- shooter spectrum of GRB 240218A. The results that I will present in this talk provide unique information on the metal enrichment history of the Universe, rivaling and complementing JWST surveys. Furthermore, they motivate pursuing GRBs dedicated space missions to fully exploit the possibility to use GRBs to explore the high-redshift Universe.

Speaker: Dr Andrea Saccardi (CEA)

Swift20_ANDREASACCARDI.pdf

16:45 Host galaxies and local properties of a complete sample of short Gamma-Ray Bursts

Short gamma-ray bursts (SGRBs) represent a unique class of cosmic events offering valuable insights into the physics of compact object binary systems. From the combined detection of the gravitational wave (GW) event GW170817 with the corresponding electromagnetic counterparts - the kilonova AT2017gfo and the short GRB170817A - interest in compact object binary merger counterparts has significantly increased, leading to extensive follow-up campaigns by ground-based and space telescopes. The Neil Gehrels Swift Observatory (Swift) fast re-pointing capability and precise X-ray afterglow localization by the Swift X-Ray Telescope (XRT) have enabled to secure a noteworthy amount of quality data to perform population statistical studies and shed light on the formation, evolution, and merger of these systems. For this purpose, a sample of short GRBs - the S-BAT4 - has been set up, collecting properties from 2004 to 2022, by means of precise selection criteria in terms of flux limitation and completeness, in order to ensure minimal observational and redshift-related biases. In the talk, I will present the analysis of the environmental properties of S-BAT4 events, including host galaxy features, offsets, and neutral hydrogen column densities (NH) derived from Swift/XRT spectra. Host galaxy properties and magnitudes have been analysed in comparison to carefully selected samples of field galaxies, as well as typical galaxies of long GRBs (LGRBs), to investigate how the environment plays a role in the GRB progenitor systems. Host galaxies of SGRBs have been found to be consistent with bright, mainly star-forming galaxies, with significant differences from LGRB hosts. Specifically, SGRB hosts display higher masses and gas-phase metallicities, while exhibiting lower star formation rates. Offsets and NH have been computed for a significant fraction of S-BAT4 events and analyzed in relation to both host and afterglow properties to shed light on different formation channels for compact object binary systems. Although of low significance, hints for different classes of SGRBs have been found in the distributions of the two parameters, while the offset, normalized to the size of the associated host galaxy, has been found to be correlated with the mass of the host.

Speaker: Matteo Ferro (Istituto Nazionale di Astrofisica (INAF))

Swift20_MF.pdf

17:00 Properties of the populations of Gamma Ray Bursts

The intrinsic properties of short and long Gamma-Ray Bursts (GRBs), including their cosmic rates, luminosity functions, and potential evolution with redshift, can be studied by integrating data from large GRB samples collected over the past 50 years. These datasets offer diverse observational constraints, with Swift providing the most extensive sample of GRBs with measured intrinsic properties, enabling more accurate control of selection biases in population studies.
Both direct and indirect methods indicate that long and short GRBs share similar luminosity functions but exhibit distinct cosmic evolution in their volumetric rates. These differences may reflect evolutionary changes in progenitor properties (e.g., jet structure) or delayed mergers relative to the time of binary formation. Present and future observatories designed to detect low-luminosity GRBs and those at the highest redshifts will be pivotal in uncovering new insights into GRB progenitors, jet structures, and emission mechanisms. I will present the state of the art in GRB population studies based on parametric modelling of combined observational properties and discuss how upcoming missions may address outstanding questions in the field.

Speaker: Giancarlo Ghirlanda (Istituto Nazionale di Astrofisica (INAF))

Ghirlanda_Giancarlo.pdf

17:15 Teaching an old BAT new tricks: New analysis methods and results with Swift/BAT-GUANO

In 2017 the detection of the faint GRB 170817A jointly with gravitational waves vaulted us into the era of multi-messenger astronomy, but it also showed us the need for an increased sensitivity to faint GRBs. This motivated efforts to develop sensitive, targeted searches for GRBs that run on the ground. The Gamma-ray Urgent Archiver for Novel Opportunities (GUANO) came online in 2019 to fill the need of having the full resolution Swift/BAT data delivered to the ground on command. With data available, more sensitive analyses were able to be performed. The most sensitive being the Non-Imaging Transient Reconstruction and Temporal Search (NITRATES), a forward-folding, likelihood-based analysis that has improved the detection rate of GRB 170817A-like bursts by a factor of ~3 over the status quo. The combination of GUANO data and the NITRATES analysis has lead to a ~60% increase in the number of short GRBs localized to an arcminute scale by Swift/BAT over the past few years. The functionality of the NITRATES analysis has recently been expanded to perform inference over the whole sky, creating localization skymaps for GRBs that are either too weak to be localized to a single arcminute-scale peak or originate from outside BAT's coded field of view. For optimal orientations, localizations for bursts outside the coded field of view can be as small as ~100 square degrees, rivaling the localization capability of scintillator based instruments. Coded aperture instruments make it possible to resolve gamma-rays and hard x-rays, and the NITRATES analysis is a novel technique that can greatly increases their functionality and sensitivity to transients.

Development is currently underway on a joint, coherent analysis of Swift/BAT and Fermi GBM data. This analysis would merge each instruments' strengths and effective areas while having mostly independent backgrounds, resulting in the most sensitive search possible for weak GRBs. This analysis will hopefully create a framework for analysis of a network of gamma-ray detectors that allows for very different instrument properties. Work is also under way on further analyses that can detect and possibly localize weak GRBs in continuous Swift/BAT data products with limited resolution.

In this talk I will discuss the needs for sensitive gamma-ray transient searches, the basics of the NITRATES analysis, and highlight some results made possible by GUANO and NITRATES, including extensive limits set on prompt GRB emission around gravitational wave events and the detection of "delayed" gamma-rays from the Einstein Probe transient EP240315a. I will end the talk with a discussion of ongoing development on further analyses that will hopefully be able to be applied to the long history of archival Swift data and to future instruments.

Speaker: Jimmy DeLaunay (Penn State)

Swift20_Talk_JJD.pdf

17:30 → 18:00 GRB, GW and Kilonovae

17:30 Impact of Systematic Modeling Uncertainties on Kilonova Property Estimation

Precision measurements of kilonova properties like ejecta mass, geometry, and velocity are critical to informing our understanding of neutron star mergers, the neutron star equation of state, and their contribution to the r-process enrichment of the universe. Estimates of these properties are highly model-dependent and often do not incorporate the systematic uncertainties due to unconstrained atomic, nuclear, and astro-physics. In this talk, I will explore the impacts of how underlying physical assumptions like atomic data, thermalization efficiency, and geometry affect inferred kilonova ejecta properties and their spectral/photometric evolution as well as the unique ability that Swift possesses to progress kilonova science. As more kilonovae are discovered by facilities like LSST and LIGO, early time UV/optical data will be vital to understanding the long-standing mysteries surrounding kilonovae such as the origins of each kilonova component and the connection between kilonovae and long GRBs, which can only be enabled by the rapid ToO response times and wavelength coverage of Swift.

Speaker: Daniel Brethauer (UC Berkeley)

Impacts of Systematic Uncertainties on KN Parameter Estimation.pptx (1).pdf

17:45 Where has all the r-process gone? An Exploration of the Capacity for Swift GRB-Kilonovae to Enrich their Host Galaxies

In its 20 years, Swift has provided fundamental clues towards understanding the source(s) of heavy “r-process” elements (A > 130; e.g., gold, platinum, uranium) in the Universe. Indeed, with Swift’s precise burst localization capabilities, 11 GRBs have been associated with probable kilonovae (KNe), the transients produced from neutron star (NS) mergers powered by the radioactive decay of r-process elements. These discoveries, along with the KN associated with GW-detected NS merger 170817, have secured NS mergers as the only observed source of r-process in the Universe. However, it remains unknown how much r-process from NS mergers is incorporated into star-forming gas to produce r-process enhanced stars: a vital piece of information as nearly all other predictions of the amount of r-process mass in the Universe are estimated from stellar r-process abundances. In this talk, I discuss how merger location and host galaxy properties influence the capacity for an environment to be enriched. Using a population of 86 Swift-detected, merger-driven GRBs (z<3) with confident host galaxy associations and a diverse range of host stellar population properties, I present a novel analysis to quantify the timescale of these events to enrich their hosts and the amount of newly-formed stellar mass in their hosts that procures r-process material. I probe how much r-process is likely “lost”, never being reincorporated in to stars, and whether NS mergers can be the dominant source of observed r-process elements in the Universe. I conclude with emphasizing how continued Swift discoveries will lend deeper insight into the possible channels of r-process in the Universe.

Speaker: Anya Nugent (Center for Astrophysics | Harvard & Smithsonian)

Nugent_Anya_Swift20.key

Nugent_Anya_Swift20.pdf

Wednesday 26 March

09:00 → 10:15 GRB, GW and Kilonovae

09:00 Multi-messenger studies with GRBs: situation and perspectives

TBD

Speaker: Paolo D'Avanzo (Istituto Nazionale di Astrofisica (INAF))

Swift20_GRB_GW_paolo_davanzo.pdf

09:30 The impact of Swift on gravitational wave astronomy

Swift is an ideal discovery machine to detect, characterize and precisely localize the electromagnetic counterpart of gravitational waves (GWs). In this presentation, I will review the latest advancements on the systematic monitoring by Swift of GWs detected during the current and previous observing runs of the LIGO-Virgo-KAGRA collaboration. I will discuss possible joint coincidences identified by the Swit-BAT subthreshold search, made possible by the GAUNO-NITRATES infrastructure. I will examine the collection of non-detections of gamma-ray counterparts to GWs, exploring their implications for understanding the connection between GRB and GW populations. Finally, I will outline future improvements Swift can implement to further enhance its impact on multi-messenger astronomy and emphasize the invaluable legacy Swift leaves for this field, particularly for space telescopes that will operate in synergy with next-generation GW detectors.

Speaker: Dr Samuele Ronchini (PennState University)

Swift20_Ronchini.pdf

09:45 The Diversity of Electromagnetic Counterparts to Neutron Star Mergers Revealed by Swift

To date, Swift is the most successful discovery engine of the electromagnetic counterparts to neutron star (NS) mergers. In its two decades, Swift has revealed dozens of on-axis afterglows, several kilonovae, and a surprising signal from NS mergers: long-duration GRBs. In this talk, I will present our compilation of NS merger counterparts observed following Swift GRBs and modeled in a uniform way. Our analysis reveals significant diversity in both kilonova and NS merger jet properties, in line with theoretical predictions for heterogenous binary progenitor systems. I will highlight our result that the kilonova ejecta masses of merger-driven long GRBs favor an asymmetric binary progenitor, such as an NS-black hole merger. Finally, I will comment on how GW170817 compares to the population of NS mergers observed following Swift GRBs, and discuss the implications of our studies for multi-messenger astronomy in O4, O5 and beyond.

Speaker: Jillian Rastinejad (Northwestern University)

25_Mar_Swift.pdf

10:00 Gravitational-Wave Follow-Up Strategy for the UltraViolet EXplorer (UVEX) Mission

The UltraViolet EXplorer (UVEX) is a Medium-Class Explorer (MIDEX) mission selected by NASA for launch in 2030. UVEX will conduct an unprecedented all-sky time-domain survey in two UV filters. UVEX will follow up GW binary neutron star mergers as targets of opportunity, rapidly scanning across their localization regions to search for their kilonova counterparts. Early-time multiband ultraviolet light curves of kilonovae are key to explaining the interplay between jet and ejecta in binary neutron star mergers. Owing to high Galactic extinction in the ultraviolet and UVEX’s large field of view, variation in sensitivity across the GW region of interest is an important consideration for observation planning. We present a strategy for GW follow-up with UVEX in which exposure time is adjusted for each field individual to maximize the overall probability of detection. We have implemented this strategy in an open source astronomical scheduling toolkit called M4OPT (Multi-Mission Multi-Messenger Observation Planning Toolkit), on GitHub at https://github.com/m4opt/m4opt.

Speaker: Brad Cenko (NASA Goddard Space Flight Center)

singer-transients-swift-2025-03-PDF.pdf

10:15 → 10:45 Coffee break

10:45 → 12:30 The next decade of GRB science (challenges & missions)

10:45 The next decade of GRB science: the Swift legacy

TBD

Speaker: Maria Grazia Bernardini (Istituto Nazionale di Astrofisica (INAF))

bernardini.pdf

11:15 The SVOM mission

TBD

Speaker: Bertrand Cordier (CEA)

SVOM_Florence_BC_V4.pdf

11:45 First Gamma-Ray Burst observations with SVOM

Since its launch on June 22, 2024, SVOM has already detected several tens of gamma-ray bursts. We propose to present the observations and initial analyses of the first, best-characterized SVOM gamma-ray bursts. We will show that these first detections clearly demonstrate SVOM ability to probe the gamma-ray burst population in all its diversity and characterise the prompt and afterglow emission of a wide range of events: classical long bursts such as GRB241025A at 4.2 or GRB 241030B at z =2.82, short bursts with extended emission such as GRB240821A at z=0.24, X-ray Flashes such as GRB241001A at z=0.57, etc. Some of these events have also been detected by Swift/BAT, Fermi/GBM or Einstein Probe/WXT: we will illustrate the specific contribution of SVOM instruments and how they complement the observations made by these other missions. We will conclude with the encouraging prospects offered by these initial results for advancing our understanding of gamma-ray bursts and their progenitors.

Speaker: Frédéric Daigne (Institut d'Astrophysique de Paris, Sorbonne Université)

SVOM_Florence_FD_v7.pdf

12:00 Swift and the Future of TDAMM Astronomy

The Neil Gehrels Swift Observatory was designed to catch Gamma-Ray Bursts on the fly. However, with it's combination of rapid response capabilities, fast slewing and multi-wavelength instrumentation, it will likely be remembered for being the Epochal mission for the burgeoning field of Time Domain and Multi-Messenger Astrophysics (TDAMM). In this talk I will, with the aid of science results, demonstrate the evolution of Swift's capabilities that have allowed it to be more responsive to TDAMM priorities than ever. This has been enabled by a unique operations set-up that co-locates the flight operations and science operations teams, and a constantly innovating team that never believed that Swift's operations software was finished. I highlight several recent breakthroughs, including the observation of an FRB by XRT/UVOT at T0+1.9 mins, triggered by CHIME. I also discuss future capabilities that are coming to Swift in 2025. Finally, I talk about how future missions can leverage the heritage that Swift is building every day, to enable the next generation of rapid response TDAMM missions.

Speaker: Prof. Jamie Kennea (Penn State)

Kennea Swift20 Talk.pdf

12:15 The Transient High-Energy Sky and Early Universe Surveyor (THESEUS)

The Transient High-Energy Sky and Early Universe Surveyor (THESEUS) is a mission concept, developed by a large European collaboration, under study by ESA since 2018 and currently one of the three candidate M7 mission for a launch in the second half of the 30s, aiming at fully exploiting Gamma-Ray Bursts for investigating the early Universe and as key phenomena for multi-messenger astrophysics. In particular, by providing an unprecedented combination of X-/gamma-ray monitors, on-board IR telescope and spacecraft autonomous fast slewing capabilities, THESEUS will be a wonderful machine for the detection, multi-wavelength characterization and redshift measurement of any kind of GRBs and many classes of X-ray transients, including high-redshift GRBs for cosmology (pop-III stars, cosmic reionization, SFR and metallicity evolution up to the “cosmic dawn”) and electromagnetic counterparts to sources of gravitational waves. THESEUS will also provide breakthrough measurements of GRB prompt and afterglow emission, as well as the detection and multi-wavelength characterization of many classes of high-energy transients. In all these s respects, THESEUS will thus provide an ideal synergy with the very large astronomical facilities of the future working in the e.m. (e.g., ELT, TMT, CTA, SKA, Athena) and multi-messenger (e.g., Einstein Telescope, Cosmic Explorer, km3NET) domains.

Speaker: Lorenzo Amati (Istituto Nazionale di Astrofisica (INAF))

amati-theseus-swift20.pptx

12:30 → 14:00 Lunch

14:00 → 14:30 Poster Session: Poster view

14:30 → 15:45 Magnetar and pulsars

14:30 Magnetar birth rates, evolution, and their imprint in the transient X-ray sky

Magnetars, the most magnetized neutron stars in the universe, present
a fascinating but yet enigmatic population. Their birth rates,
evolutionary paths, and connection to the broader neutron star
population remain open questions in astrophysics. In this talk, I will
explore recent insights into magnetar formation rates, their relation
to core-collapse supernovae, and their presence in transient X-ray
sky. Thanks to Swift, and subsequent advent of sensitive all-sky
monitors and deep X-ray observations, we are witnessing an era of
unprecedented discovery in high-energy astrophysics. I will discuss
how these new observations challenge traditional views on magnetar
populations, and shed light on their link to other exotic
extra-Galactic transients.

Speaker: Dr Nanda Rea (Instituto de Ciencias del Espacio (ICE-CSIC, IEEC))

15:00 Giant Flares from extragalactic magnetars

Magnetars, isolated neutron stars powered mainly by magnetic energy, are characterized by variability spanning a broad interval in dynamic range and duration, from short bursts of a few milliseconds to outbursts lasting several months or even years. The most extreme variability events are the giant flares, which can be observed also from magnetars at extragalactic distances (farther than the Magellanic Clouds).

Although it is difficult to distinguish extragalactic magnetar giant flares (MGFs) from short GRBs, a few such events have been identified. This small sample has recently increased with the precise localization of 231115A in the starburst galaxy M82, and with the discovery of other candidates such as 200415A and 180128A in NGC 253, and 070222 in M83. Thanks to this increased sample it is now possible to derive tighter constraints on the rate of occurrence of giant flares, an important information to understand the evolution and dissipation of magnetic field in these extreme neutron stars.

In this talk I will review the most recent observational and theoretical advances on galactic and extragalactic MGFs, including the constraints derived from a systematic search of MGFs in the Virgo cluster of galaxies and the very recent discovery of another MGF candidate with INTEGRAL.

Speaker: Dr Sandro Mereghetti (Istituto Nazionale di Astrofisica (INAF))

mereghetti_sandro.pdf

15:15 Systematic study of magnetar outbursts

I will present a comprehensive analysis of all known magnetar outbursts observed up until 2018. This study utilizes over 1000 X-ray observations from the Neil Gehrels Swift Observatory, supplemented by a hundred observations from Chandra, XMM-Newton, and other observatories. By tracking the temporal evolution of soft X-ray spectral properties and luminosities, and by empirically modeling light curves, we estimated decay timescales and energetics for each outburst. We investigated correlations among key quantities - such as peak and quiescent luminosities, outburst energies, decay rates, magnetic field strengths, and characteristic ages. These analyses revealed significant patterns that support models of internal crustal heating and twisted magnetospheric bundles for magnetar outbursts. I will introduce the Magnetar Outburst Online Catalogue, an interactive database designed for accessing all spectral files and visualizing the derived parameters, and discuss plans to update the catalogue in the near future to include outbursts detected in recent years.

Speaker: Francesco Coti Zelati (Institute of Space Sciences (ICE, CSIC))

CotiZelati_Swift20.pdf

15:30 A Tale for Two Class of X-ray Pulsars: Two Decades of Swift Sky Observations

With 20 years of nearly continuous sky observation Swift has enabled studies of objects from several different classes. Among these, I will focus on the impulsive behavior of magnetars and the long-term evolution of pulsating ultra-luminous X-ray sources (PULXs). Magnetars are neutron stars powered by their intense magnetic fields, often identified by their emission of powerful X-ray bursts lasting from a few milliseconds to several minutes. Over its mission, Swift's BAT has recorded thousands of these events, providing us with the opportunity to conduct detailed studies of this phenomenon, under the hypothesis that they are primarily magnetically trapped fireballs. Pulsating ULXs are X-ray pulsars found in distant galaxies. These pulsars are likely accreting material at super-Eddington rates, with luminosities reaching up to 10^41 erg/s. The physics behind their extreme properties is still under debate, and much information remains hidden in archived data. In this talk, I will discuss the potential and results of monitoring programs (in particular those of Swift/XRT), which have observed several galaxies within approximately 30 Mpc of the Milky Way. Finally, a possible new way to find new candidate PULXs will be also outlined.

Speaker: GianLuca Israel (Istituto Nazionale di Astrofisica (INAF))

Swift20 GLIsrael.pdf

15:45 → 16:15 Novae and X-ray binaries

15:45 Recurrent Swift observations of recurrent novae

With its rapid response capabilities and daily planning of its
observing schedule, the Neil Genrels Swift Observatory is ideal for
following up transient objects. Over the 20 years since launch, Swift
has observed a large number of novae, from classical to recurrent, and
Galactic to extra-galactic. This sample includes four recurrent novae
which have each been followed through repeated eruption cycles. In
this talk I will present results from these sources, comparing and
contrasting the evolution from their multiple outbursts, in both the
spectral and temporal domains.

Speaker: Dr Kim Page (University of Leicester)

Page_Kim.pdf

16:15 → 16:45 Coffee break

16:45 → 18:00 Novae and X-ray binaries

16:45 A New Sample of Transient Ultraluminous X-Ray Sources Serendipitously Discovered by Swift/XRT

Ultraluminous X-ray sources (ULXs) are our best laboratories for studying extreme super-Eddington accretion. Most studies of these objects are of relatively persistent sources; however, there is growing evidence to suggest a large fraction of these sources are transient. I will present results from Brightman et al (2023) on a sample of five newly reported transient ULXs in the galaxies NGC 4945, NGC 7793, and M81 serendipitously discovered in Swift/XRT observations. Swift monitoring of these sources have provided well-sampled lightcurves, allowing for us to model the lightcurves with the disk-instability model of Hameury & Lasota, which implies durations of 60-400 days and that the mass-accretion rate through the disk is close to or greater than the Eddington rate. Of the three source regions with prior Hubble Space Telescope imaging, color-magnitude diagrams of the potential stellar counterparts show varying ages of the possible stellar counterparts. Our estimation of the rates of these sources in these three galaxies is 0.4-1.3 yr-1. We find that, while persistent ULXs dominate the high end of galaxy luminosity functions, the number of systems that produce ULX luminosities are likely dominated by transient sources.

Speaker: Murray Brightman

Transient ULXs Swift 20.pdf

17:00 The legacy of the Swift Supergiant Fast X-ray Transients Project

The Swift Supergiant Fast X-ray Transients Project was born 18 years ago as one of the initiatives to boost secondary science. It exploited Swift's fast automatic slewing, multi-wavelength capability, its flexible observing schedule and very low overheads to detect, characterise, and understand the physics underlying Supergiant Fast X- ray Transients (SFXT), high-mass X-ray binaries with an O-B supergiant displaying X-ray outbursts reaching luminosities of $10^{38}$ erg s$^{-1}$ and surprising large dynamic ranges. The strategy combined follow-ups of outbursts, when detailed broad-band spectroscopy is possible, with long-term monitoring campaigns, when the out-of-outburst fainter states can be observed. Several fundamental discoveries can be attributed to this simple but effective plan: the record luminosity in an SFXT outburst (up to the Eddington luminosity for a 1.4M$_{\rm sun}$ neutron star) bringing the dynamic range up up to a factor of 1 million, a quantification of an intermediate flux state where SFXTs spend most of their time, and a variability detected at all timescales that have been probed.
The lasting legacy of this project now includes two catalogues based on the first $\sim100$ months of the Swift mission. The first is a collection of over a thousand Swift/BAT flares from 11 SFXTs, with immediate applications of an estimate of the expected number of SFXTs in the Milky Way, and the number of flares expected from other future missions. The second includes all the SFXT Swift onboard (GRB-like) triggers and provides tools to predict whether a transient with no X-ray counterpart may be an SFXT candidate, tools can be exploited to develop future X-ray missions with large FoV instruments.
The year 2025 marks the 20th anniversary of the recognition of SFXTs as a class of astrophysical sources, and we highlight the Swift future initiatives to continue their investigation.

Speaker: Dr Patrizia Romano (Istituto Nazionale di Astrofisica (INAF))

Romano_SFXTs_Swift20.pdf

17:15 Unveiling the hard X-ray emitting population of accreting white dwarf binaries: the Swift role

The Swift/BAT survey, thanks to the uniform exposure over the sky, has offered an unique opportunity for galactic population studies. In particular in the recent years a large number of hard X-ray emitting white dwarf binaries have been detected, the majority identified with follow-up observations as magnetic accretors. These systems have been longly supposed to constitute the dominant component of the Galactic Ridge and bulge making their study crucial not only for population studies but also to understand close binary evolution.
Furthermore, a wide dynamic and unpredictable variability (high and low
states, outbursts) characterise the X-ray emission of these accreting white dwarfs. Thanks to its observing flexibility Swift with its X-ray and UV/optical instruments, has played a crucial role in their transient behaviour, allowing follow-up detailed studies.
An outlook will be given on the most relevant results

Speaker: Dr Domitilla de Martino (INAF - Capodimonte Observatory Naples)

deMartino_Domitilla.pdf

17:30 Insights from the Swift satellite on Black Hole X-ray Binaries

The Burst Alert Telescope (BAT) is currently the only hard X-ray telescope operating above 15 keV that is capable of continuously monitoring the outbursts of galactic X-ray binaries. This unique capability enables us to investigate the long-term spectral evolution of black hole X-ray binaries and facilitates the initiation of multiwavelength observations during specific phases of these outbursts. In my presentation, I will discuss the findings from our BAT and XRT monitoring campaigns, as well as the simultaneous multiwavelength observations conducted on a selected sample of black hole transients.

Speaker: Melania Del Santo (Istituto Nazionale di Astrofisica (INAF))

DelSanto_Swift20.pdf

17:45 Completing 20 years of X-ray monitoring of the Galactic Center: A Swift legacy

The center of our Galaxy has been monitored with the Swift/XRT almost every day since 2006. Through the unique combination of high cadence and good X-ray sensitivity, this program provided excellent means to capture X-ray flares from the supermassive black hole Sgr A*, to study the accretion properties of 16 transient X-ray binaries, and to discover new X-ray transients. This talk will review the research highlights of nearly 20 years of Swift's X-ray monitoring of the Galactic center.

Speaker: Nathalie Degenaar (University of Amsterdam)

Degenaar_Swift20.pdf

19:45 → 22:45 Social dinner - Osteria dei Baroncelli

Thursday 27 March

09:00 → 10:30 Multimessenger and multiwavelength Astronomy

09:00 High energy astrophysical neutrinos: Open questions and future prospects

TBD

Speaker: Prof. Eli Waxman (Weizmann Inst.)

09:30 CTAO a new window for the multi-messenger and multi-wavelength astronomy

The Cherenkov Telescope Array Observatory (CTAO) is the next-genration very-high energy gamma-ray observatory with two observation stations, one in the Canary island of La Palma (Spain) and the other in the Paranal desert in Chile. Designed to operate for 30 years, the CTAO will function as an open, proposal-driven facility, offering access to researchers worldwide.
The CTAO is nearing a pivotal moment, positioning itself as a key player in both multi-messenger and multi-wavelength astronomy. Currently under construction, it is expected to deliver its first data with intermediate array configurations within the next three years. Surpassing existing Cherenkov telescope arrays, already these initial configurations will enable groundbreaking science results. With full capabilities for detecting short-duration phenomena, the early science program of the CTAO will place a strong emphasis on transient events—key drivers in the multi-messenger and multi-wavelength astronomy landscape. This contribution will provide an update on the status of the CTAO construction project, with a focus on the scientific capabilities of the first intermediate array configurations and their significance within the broader multi-messenger and multi-wavelength context.

Speaker: Antonio Stamerra (Istituto Nazionale di Astrofisica (INAF))

10:00 The contributions of ESO to Swift followup over 20 years

The powerful array of instruments and flexible rapid response provided by the European Southern Observatory has led to it playing a major role in the science enabled by Swift in the past 20 years. This has included obtaining numerous redshifts, observations of breakthrough events (including several of the highest redshift GRBs) and their host galaxies, and building up of statistical samples allowing exploration of cosmic evolution of their environments. The STARGATE collaboration, building on foundations laid by previous groups, has provided the vehicle for exploiting ESO telescopes for the past several years. I will review some of these highlights, and consider the future role of ESO in high energy transient science in the future as we move into the 30m class era.

Speaker: Nial Tanvir (University of Leicester)

Tanvir_Florence_Swift20_2025.pptx

10:15 Swift's crucial role in the Einstein Probe era of Fast X-ray Transients

Fast X-ray Transients (FXTs) are minute-to-hours long flashes of
X-rays, first discovered serendipitously in X-ray satellite data
(e.g., Chandra, XMM-Newton, and Swift). They are proven to be caused by
energetic extra-galactic phenomena. Currently, Einstein Probe is
revolutionizing the field by discovering many FXTs and, crucially, by
their low-latency announcement thereof. These extra-galactic FXTs are
ubiquitous: their density rate is several hundred per year per
Mpc^3. FXTs have been proposed to arise from double neutron star
mergers, tidal disruption events involving an intermediate-mass black
hole and a white dwarf, and from off-axis or sub-luminous gamma-ray
bursts. Brief extra-galactic FXTs also arise in supernova shock
breakouts. Contemporaneous multi-wavelength detections possible only
in the current Einstein Probe era show that FXTs originate from more
than 1 progenitor. Swift's (autonomous, level 0) follow-up of Einstein Probe-discovered events provides crucial rapid accurate localizations (XRT/UVOT) and early UVOT multi-wavelength information. We will discuss the most recent findings and provide some (potential) science questions to be answered using FXT observations.

Speaker: Peter Jonker

10:30 → 11:00 Coffee break

11:00 → 11:30 Multimessenger and multiwavelength Astronomy

11:00 Multiwavelength Follow-up Observations of Astrophysical Neutrino Events

On September 22, 2017, the IceCube Neutrino Observatory detected a high-energy neutrino of potential astrophysical origin which was found by follow-up electromagnetic observations to spatially and temporally coincide with the flaring state of a known blazar, TXS 0506+056. Since then, several additional neutrino events have been found in spatial correlation with known high-energy sources. Multiwavelength follow-up observations of astrophysical neutrino events such as these, and the continued monitoring of previously identified sources such as TXS 0506+056 are imperative in finding sources of the diffuse neutrino flux detected by IceCube as well as the origins of high-energy cosmic rays. Because of its rapid response times, the Neil Gehrels Swift Observatory is especially well-suited for time sensitive observations such as these. Here, we present results from Swift XRT and UVOT observations of astrophysical neutrino candidate events with potential gamma-ray counterparts, as well observations performed by the Neutron Star Interior Composition ExploreR (NICER), NuSTAR, and the Fermi Gamma-ray Space Telescope.

Speaker: RileyAnne Sharpe (The University of Alabama)

Sharpe_20YearsofSwift.pdf

11:15 The Swift Perspective of Very High Energy Sources Observed with VERITAS

VERITAS is one of the world’s most sensitive detectors of astrophysical very high energy (VHE; E> 100 GeV) gamma rays. The array is located in southern Arizona, USA and is made up of four 12-m imaging atmospheric Cherenkov telescopes (IACTs). With nearly 20 years of operation since the first telescope’s installation was complete, the instrument has been able to study Galactic sources such as the binary LS I+61 303, HESS J0632+057 and the pulsar PSR J2023+4127 (to name a few of many) as well as extragalactic sources such as the radio galaxy M87, and nearly 50 different VHE-emitting blazars. Over the lifetime of VERITAS, Swift has contributed to deep, long-term studies of known VHE blazars, provided first time X-ray measurement of candidate VHE blazars, and has aided in the discovery of VHE emission from unique blazars such as OJ 287. Many of the objects observed by VERITAS are remarkably variable, and benefit from the flexible and rapid response of the Swift satellite, which provides direct measurement of the X-ray photons that are demonstrably associated in some way with the VHE photons emitted by the sources. The synergy provided by contemporaneous observations of these objects by VERITAS and Swift has enabled remarkable progress in the understanding of how the VHE photons are produced. A brief survey of results made possible by these joint observations will be provided.

Speaker: Amy Furniss (UC Santa Cruz)

Swift20YearCelebration_VERITAS.pdf

11:30 → 12:30 Thermonuclear Supernovae, Core-Collapsed Supernovae and FBOTs

11:30 An Ultraviolet View of Thermonuclear Supernovae

TBD

Speaker: Prof. Peter Brown (Texas A&M University)

12:00 Extragalactic fast X-ray transient from a weak relativistic jet associated with a Type Ic-BL supernova

Massive stars end their life as core-collapse supernovae, amongst which some extremes are Type Ic broad-lined supernovae associated with long-duration gamma-ray bursts (LGRBs) having powerful relativistic jets. Their less-extreme brethren make unsuccessful jets that are choked inside the stars, appearing as X-ray flashes or low-luminosity GRBs. On the other hand, there exists a population of extragalactic fast X-ray transients (EFXTs) with timescales ranging from seconds to thousands of seconds, whose origins remain obscure. Known sources that contribute to the observed EFXT population include the softer analogs of LGRBs, shock breakouts of supernovae, or unsuccessful jets. Here, we report the dis- covery of the bright X-ray transient EP240414a detected by the Einstein Probe (EP), which is associated with the Type Ic supernova SN 2024gsa at a redshift of 0.401. The X-ray emission evolution is characterised by a very soft energy spectrum peaking at < 1.3 keV, which makes it distinct from known LGRBs, X-ray flashes, or low-luminosity GRBs. Follow-up observations at optical and radio bands revealed the existence of a weak relativistic jet that interacts with an extended shell surrounding the progenitor star. Located on the outskirts of a massive galaxy, this event reveals a new population of explosions of Wolf-Rayet stars characterised by a less powerful engine that drives a successful but weak jet, possibly owing to a progenitor star with a smaller core angular momentum than in traditional LGRB progenitors.

Speaker: Hui Sun (National Astronomical Observatories, Chinese Academy of Sciences)

SUN_Hui.pdf

12:15 Swift as an Unprecedented Probe of Young, CSM-Interacting Supernovae

There is now an amalgam of observational evidence that massive stars undergo enhanced and/or eruptive mass-loss in their final years before explosion. In this talk, I will present multi-wavelength observations of >40 type II SNe whose very early-time ("flash") spectra showed transient, narrow emission lines from shock interaction with confined circumstellar material (CSM) around their red supergiant (RSG) progenitor stars prior to shock breakout. I will discuss the observational properties of this "flash spectroscopy" SN sample, the largest to date, and how Swift-UVOT provided both crucial early-time coverage at UV wavelengths as well as direct evidence that UV emission is an essential metric for understanding CSM-interaction. This sample also includes the CSM-interacting type II SNe 2023ixf and 2024ggi, the closest and brightest SNe of the decade, for which I will present direct evidence of shock breakout emission as detected by Swift-UVOT. Lastly, I will discuss how robust modeling of such events with non-LTE radiative transfer codes is bolstered by early-time Swift-UVOT light curves and how such modeling allows for direct constraints on the mass-loss histories of the RSGs in their final years. Lastly, I will highlight on-going efforts for automatic Swift triggering on infant SNe discovered by the Zwicky Transient Facility and future prospects for probing the UV parameter space of young, CSM-interacting SNe.

Speaker: Dr Wynn Jacobson-Galan (California Institute of Technology)

WynnJacobsonGalan_Swift.pdf

12:30 → 14:00 Lunch

14:00 → 14:30 Poster Session: Poster view

14:30 → 16:20 Thermonuclear Supernovae, Core-Collapsed Supernovae and FBOTs

14:30 Swift@ASAS-SN: The Role of Swift for the All-Sky Automated Survey for Supernovae

TBD

Speaker: Prof. Chris Kochanek (Department of Astronomy, The Ohio State University)

14:50 AT2024wpp and Luminous Fast Blue Optical Transients: New Developments from Swift and HST

The rare and mysterious class of events sometimes known as luminous fast blue optical transients (LFBOTs), typefied by the event AT2018cow, has provided a steady stream of surprises over the past seven years. LFBOTs radiate primarily in the UV, are extremely radio-luminous, are highly X-ray variable, and at least in some cases they produce ultra-fast optical flares for months and leave behind a hot remnant. Their origins remain unclear: they may originate from the direct collapse of a massive star to a black hole, or from the disruption of a star by an intermediate mass black hole. Swift has proven to be critical for the study of these events: its flexible scheduling and simultaneous UV and X-ray capabilities make it ideal for confirming the discovery of a new LFBOT and for studying its early-phase evolution. I will briefly review what we have learned about this class of events to date, with particular emphasis on the newly-discovered AT2024wpp, the nearest and best-studied LFBOT since AT2018cow. Results from our multi-wavelength campaign on this object (spanning from radio to X-ray wavelengths, and including HST FUV spectroscopy) will be discussed, with implications for the nature of LFBOTs.

Speaker: Daniel Perley (Liverpool John Moores University)

Swift_Perley_24wpp.pptx

15:05 BTSbot-nearby: Rapid, autonomous follow-up of nearby infant supernovae with Swift/UVOT

Despite great advances in our understanding of transients over the ~20 years of Swift operations, it remains extremely challenging to link a transient to a progenitor with certain properties and to constrain the final phases of its life. Very early follow-up of supernovae (SNe), however, can provide critical insights into the progenitor: flash spectroscopy can reveal short-lived CSM interaction in core-collapse SNe and an early UV flux excess is a possible signpost for companion interaction in Type Ia SNe. These features are ephemeral, typically requiring rapid multi-wavelength follow-up to be well characterized, but traditional follow-up workflows require human action which can add hours to days of latency. We present “BTSbot-nearby,” a machine learning-based tool which fully autonomously identifies and triggers target-of-opportunity (ToO) follow-up for nearby (D<60 Mpc) young (<48 hours since first light) transients. BTSbot-nearby autonomously identified the recent Type IIP SN 2024jlf and obtained a spectrum showing flash ionization features just 7 minutes after the trigger and 17 hours after first light. SN 2024jlf’s UV light curve, collected by Swift/UVOT, provided crucial constraints when matching to sophisticated radiative hydrodynamic models and inferring the progenitor’s mass-loss rate shortly prior to explosion ($10^{-3} M_\odot$ yr$^{-1}$), a key parameter which is best constrained in the UV. In collaboration with the Swift team, BTSbot-nearby now autonomously triggers “urgency 0” ToOs to Swift/UVOT for new transients it identifies. This technology is at the very forefront of expediting follow-up for new, important transient events, and the integration with Swift will maximize the chances of observing early-time UV phenomena which informs us to the nature of the transient and its progenitor.

Speaker: Nabeel Rehemtulla (Northwestern University)

NRehemtulla_Swift20.pptx

15:20 Characterization of a peculiar Einstein Probe transient EP240408a

We present the results of our multi-wavelength (X-ray to radio) follow-up campaign of the Einstein Probe transient EP240408a. The initial 10 s trigger displayed bright soft X-ray (0.5-4 keV) radiation with a peak luminosity of 1e49 (1e50) erg/s for an assumed redshift of z=0.5 (2.0). The Neil Gehrels Swift Observatory and Neutron star Interior Composition ExploreR discovered a fading X-ray counterpart lasting for 5 d (observer frame), which showed a long-lived (4 d) plateau-like emission before an extremely sharp powerlaw decline. The plateau emission was in excess of 1e46 (1e47) erg/s at z=0.5 (2.0). Deep optical and radio observations resulted in non-detections of the transient. Our observations with Gemini South revealed a faint potential host galaxy near the edge of the X-ray localization. The faint candidate host, and lack of other potential hosts to deep limits, implies a higher redshift origin, which produces extreme X-ray properties that are inconsistent with many known extragalactic transient classes. In particular, the lack of a bright gamma-ray counterpart, as constrained by GECam-B and Konus-Wind, conflicts with known gamma-ray bursts (GRBs) of similar X-ray luminosities. We therefore favor a jetted tidal disruption event (TDE) as the progenitor of EP240408a at high-z, possibly caused by the disruption of a white dwarf by an intermediate mass black hole. The alternative is that EP240408a may represent a new, previously unknown class of transient.

Speaker: Brendan O'Connor (Carnegie Mellon University)

EP240408a-Swift-Florence-March2025-OConnor.pdf

15:35 The Catalog of Extragalactic Fast X-ray Transients Discovered by Einstein Probe during its Commissioning Phase

Extragalactic Fast X-ray Transients (eFXTs) are defined as short flares in X ray with cosmological origins. But the nature of eFXT is still uncertain due to the lack of timely follow up observations. The possible physical mechanisms include the shock breakout of a supernova, the fireball phase of a nova, the magnetar powered X-ray emission after the mergers of binary neutron stars, off-axis GRBs and other unexplored objects. Benefiting from its unprecedentedly large field of view and high sensitivity in the soft X-ray band, the Wide field X-ray Telescope (WXT) on board Einstein Probe (EP) satellite has detected a few dozens of eFXTs during its commissioning phase. The near real time alert and quick autonomous follow up observations of Follow up X ray (FXT) enable the timely multi wavelength detection in some cases (e.g. EP240315a and EP240414a). These eFXTs show diverse temporal shapes and multi wavelength associations. A significant fraction of these eFXTs have no corresponding gamma ray counterparts indicating potential distinct origins from classical GRBs. In this talk, I will introduce the statistical studies of these eFXTs’ properties, aiming to obtain a comprehensive understanding of their possible physical origins.

Speaker: Qinyu Wu (National Astronomical Observatories, Chinese Academy of Sciences)

15:50 The bluest, the fastest and the X-ray bright: Core-collapse SNe and FBOTs

TBD

Speaker: Prof. Raffaella Margutti (UC Berkeley)

16:20 → 16:50 Coffee break

16:50 → 18:20 TDEs and Nuclear Transients

16:50 Probing Massive Black Hole Demographics with Tidal Disruption events

Tidal disruption events (TDEs) provide a unique window into the otherwise quiescent massive black hole (MBH) population. Sample studies of TDEs in galaxy nucleus and off-nuclear locations can address fundamental open questions about MBHs, including their origin and growth via mergers. Over the past few years, time domain sky surveys such as the optical Zwicky Transient Facility (ZTF) have led to a surge of TDE candidates. Swift follow-up observations have been instrumental in confirming bona fide TDEs and characterizing their multi-wavelength properties. In this talk, I will present our efforts to constrain the local MBH mass function using a complete, flux-limited sample of ZTF TDEs. I will also introduce AT2024tvd, the first offset TDE identified by modern optical sky surveys, and discuss its implications for galaxy evolution. Finally, I will outline strategies to optimize Swift follow-up of TDE candidates in the era of upcoming time-domain surveys.

Speaker: Dr Yuhan Yao (UC Berkeley)

yao_yuhan_pdf.pdf

17:20 Connecting the Dots: Swift’s Key Role in Unveiling the X-ray-Radio Connection in Delayed Flares from Tidal Disruption Events

Tidal disruption events (TDEs) occur when a star is torn apart by the immense tidal forces emanating from a supermassive black hole (SMBH). These events serve as dynamic laboratories for studying dormant SMBHs, their environments, and the physical processes associated with SMBHs, including the formation of accretion flows. Among the numerous enigmatic phenomena associated with TDEs, a relatively recent discovery is the occurrence of delayed X-ray and radio flares. Numerous events have been observed exhibiting sudden X-ray and radio emission at exceptionally late times, spanning from hundreds of days to several years after the initial tidal disruption. Notably, optical flaring has not been consistently associated with these flares. The origin of these delayed flares remains elusive, but several hypotheses have been proposed, including transitions in accretion states, the presence of large viewing angle off-axis jets, and recurring disruptions. The temporal and spectral characteristics of these delayed flares exhibit remarkable diversity, suggesting that they may be driven by a diverse range of processes. In my presentation, I will review several such flares that we recently observed concurrently with the Swift (X-ray) and AMI (radio) telescopes. Our initial findings, indicate a strong correlation between X-ray and radio emission in some of these events, implying a potential common mechanism.

Speaker: Assaf Horesh (The Hebrew University of Jerusalem)

Swift_20_years_Florence_2025.pdf

17:35 A tidal disruption event that turned off

Swift has made seminal contributions to the study of tidal disruption events (TDEs), in particular the discovery of three relativistic jetted TDEs and the first intermediate timescale quasi-periodic erupter. In this talk, I will discuss a unique source discovered in archival XRT data that continues this legacy. LSXPS J0956 appears, at first glance, to be a typical thermal X-ray TDE. However, unlike the majority of the sample which decay slowly and can remain luminous for a decade or more, it exhibits a precipitous decline roughly two years after initial detection. Such behaviour has been observed in TDEs before, specifically in jetted TDEs. In contrast to LSXPS J0956, these events display power law spectra, however, viscous-like interactions with the surrounding medium can induce structure in the jet. If viewed slightly off-axis, the varying optical depth could produce the quasi-thermal spectrum observed in LSXPS J0956. Alternatively, if the star’s initial orbit is sufficiently eccentric, the entirety of the debris can remain bound to the black hole. The accretion rate decays slowly before dropping rapidly as all the material is accreted, again consistent with the behaviour of LSXPS J0956. I will discuss both these models and their implications for the wider TDE population. Neither of these scenarios have previously been observed in the TDE sample making LSXPS J0956 another first of its kind discovery for Swift.

Speaker: Dr Rob Eyles-Ferris (University of Leicester)

EylesFerris_Rob.pdf

17:50 An overview of Repeating Extragalactic Nuclear Transients (RENTs): Potential Objects Orbiting Supermassive Black Holes

In the last five years, a mysterious new class of astrophysical transients have been uncovered using primarily X-ray telescopes. These sources are spatially coincident with centers of galaxies and show X-ray variations that repeat with quasi–periodicities on timescales of minutes to ~ a few years. One of the prevailing ideas for these Repeating Extragalactic Nuclear Transients (RENTs) is that they are triggered by interactions of a gravitationally bound (smaller) object with the accretion disk of a supermassive black hole (SMBH). If that is indeed the case, then some of these extreme mass ratio binaries could also be detectable with future space-based gravitational wave detectors like LISA and Taiji, and have the potential to transform our understanding of supermassive black hole growth, probe dark energy, and put fundamental constraints on gravity. I will present an observational overview of RENTs, their connection to stellar tidal disruption events and also present some state-of-the-art general relativistic hydrodynamic simulations of objects embedded in SMBH disks and argue that, in some cases, these repeating transients could be double compact object binaries with direct implications for multi-messenger astrophysics. I will highlight the critical roles of Swift/XRT and UVOT in transforming our understanding of RENTs, and will end by highlighting the exciting prospects of discovering more such systems with synergy between the Rubin/LSST observatory and various space-based X-ray, IR and UV telescopes.

Speaker: Dr Dheeraj Pasham (MIT)

Swift Florence.pdf

18:05 Holding Out for a Hero: X-ray, UV, and optical characterization of the nuclear transient AT2020afhd

AT2020afhd was first discovered in the optical by the Zwicky Transient Facility (ZTF) and reported as an X-ray-detected tidal disruption event (TDE) candidate with broad Balmer and He II emission in February 2024. Subsequent observations with Swift/UVOT and XRT revealed striking behavior, with UV characteristics comparable to optically-selected TDEs but with prominent X-ray variability. In this talk, I present the long-term optical, UV, and X-ray light curve of AT2020afhd in addition to follow-up optical spectroscopy. Using this rich suite of follow-up observations, I discuss the nature and classification of this transient and how it may help further our understanding of SMBH disk formation and accretion.

Speaker: Erica Hammerstein (University of California, Berkeley)

Friday 28 March

09:00 → 10:30 AGN: accretion and outflows, blazars and jets

09:00 X-ray/UV/optical continuum reverberation mapping in AGN with Swift

The angular size of the innermost regions of AGN are generally too small to be resolved, thus we must rely on indirect techniques to probe these regions. Reverberation mapping measures time lags between light curves of different wavelengths to estimate size scales. In the simplest picture for continuum reverberation, variable X-rays from close to the black hole irradiate an optically thick, geometrically thin accretion disk driving variations at longer wavelengths - the inner hot disk 'sees' variations before the outer cooler disk. Thus, we expect time lags that increase with wavelength, with the lags on the other of ~1 day. Before Swift, it was technically challenging to obtain good enough light curves to measure such short lags with high confidence. But, the capability of Swift to perform sub-daily monitoring of AGN for in X-rays plus 6 UV/optical filters for many months revolutionized continuum reverberation mapping studies. High cadence, high S/N, multiband light curves obtained by Swift led to high significance measurements that time lags increase with wavelength. I will review continuum reverberation in AGN, and what we have learned about the innermost regions of AGN.

Speaker: Dr Ed Cackett (Wayne State University)

09:30 The legacy of Swift-BAT: A complete census of the heavily obscured AGN population in the local Universe

I will present a summary of the results obtained in the past seven years by the Clemson-INAF Compton thick AGN project, which is based on the Palermo Swift-BAT catalog. By taking advantage of Swift-BAT effectiveness in detecting heavily obscured AGN at z~0, our group performed a multi-year, multi X-ray telescope effort aimed at obtaining a complete census of the obscured AGN population in the local Universe, while at the same time characterizing with unprecedented quality the properties of heavily obscured accreting supermassive black holes (SMBHs).
With our Swift-BAT selected, volume-limited sample, we provided the most accurate measurement of the fraction of Compton thick (i.e., with line-of-sight column density NHlos>1E24 cm-2) AGN at z<0.05 (i.e., within <~200 Mpc from us). Such a parameter is a key ingredient in AGN population synthesis model.
I will also show how we use the Palermo Swift-BAT catalog to build a large sample of heavily obscured AGN with multi-epoch X-ray observations, that are needed to characterize the properties of the clumpy medium surrounding accreting SMBHs, as well as to understand the complex feeding-feedback interplay which takes place between the SMBH and its host galaxy.

Speaker: Stefano Marchesi (Università di Bologna)

Marchesi_Swift_Firenze_20250327.pdf

09:50 Too many or just right? Massive jetted quasars in the early Universe

The formation and evolution of the first supermassive black holes have been put in the spotlight after the discovery of few hundreds extremely massive quasars at high redshift. An interesting twist in our understanding of the matter was introduced by the discovery of an unusual number of jetted sources: X-ray observations of blazars (i.e. AGN with jets aligned to our LoS) at $z>4$ prove that the most massive active black holes are preferentially hosted in jetted quasars in the first Gigayear from the Big Bang. Jets might thus play a crucial role in fast assembling and accreting matter onto supermassive black holes. Investigating their occurrence and activity is not straightforward at high z: multi frequencies observations are needed to identify them, especially at high energies where the jet dominates the emission. Swift/XRT has proved to be the most efficient instrument to study $z>4$ blazars, but lately also eROSITA comes easily into play in this picture: its sensitivity in the soft X-ray energies nicely complements existing and/or new X-ray observations for some sources, gives the much needed multiwavelength view on others, or helps in identifying brand new blazar candidates.
I will present our current knowledge about $z>4$ blazars, a population that provides a comprehensive view on jet, accretion and mass features of the $M>10^9M_\odot$ jetted quasars. I will also dive into the inconsistencies that arise from low and high-frequency observations: do jet features change across cosmic time? What is their role in the evolution of the first supermassive black holes of our Universe?

Speaker: Tullia Sbarrato (Istituto Nazionale di Astrofisica (INAF))

sbarrato_tullia.pdf

10:10 A first time in the history of astronomy: Observing the formation and evolution of a radio jet from a super massive black hole in real time.

We present results from a high cadence multi-wavelength observational campaign of the enigmatic changing look AGN 1ES 1927+654 from May 2022- April 2024, coincident with an unprecedented radio flare ~60 times in a few months and the emergence of a spatially resolved jet at 0.1-0.3 pc scales. This is the first time in the history of astronomy that we discover a jet form and evolve in real time from a supermassive black hole system. We have also detected a recurrent quasi-periodic oscillation (QPO) in the 2-10 keV band with an increasing frequency (1-2 mHz) over the same period. During this time, the soft X-rays (0.3-2 keV) monotonically increased by a factor of ~8, while the UV emission remained nearly constant with < 30 % variation and the 2-10 keV flux showed variation by a factor < 2. The weak variation of the 2-10 keV X-ray emission and the stability of the UV emission suggest that the magnetic energy density and accretion rate are relatively unchanged, and that the jet could be launched due to a reconfiguration of the magnetic field (toroidal to poloidal) close to the black hole. Advecting poloidal flux onto the event horizon would trigger the Blandford-Znajek (BZ) mechanism, leading to the onset of the jet. The concurrent softening of the coronal slope (from $\Gamma=2.70\pm 0.04$ to $\Gamma=3.27\pm 0.04$), the appearance of a QPO, and low coronal temperature ($kT_{e}=8_{-3}^{+8}$ keV) during the radio outburst suggest that the poloidal field reconfiguration can significantly impact coronal properties and thus influence jet dynamics. These extraordinary findings in real time are crucial for coronal and jet plasma studies, particularly as our results are independent of coronal geometry.

Speaker: Brad Cenko (NASA Goddard Space Flight Center)

1ES_talk_pdf.pdf

10:30 → 11:00 Coffee break

11:00 → 12:20 Swift and synergies with other facilities

11:00 The Einstein Probe mission

The Einstein Probe (EP) is designed to detect mainly high-energy transients and variables, at unprecedented sensitivity and spatial resolution in the soft X-ray band, and to perform quick and deep follow-up observations in X-rays. EP is an international collaborative mission led by the Chinese Academy of Sciences, with partners of ESA, MPE and CNES. EP was launched on January 9, 2024. EP had completed the commissioning and in-orbit calibrations by July 2024. Since then, EP has started the nominal science operations phase. This talk will introduce the instrument performance, the science operations, and preliminary results with emphasis on the transients and variables detected. Possible synergies with the Swift mission will be briefly discussed.

Speaker: Weimin Yuan (National Astronomical Observatories, Chinese Academy of Sciences)

11:20 SOXS: the transient hunter

The Son Of X-Shooter (SOXS) is a wide-band (350-2000 nm), medium-resolution (R~4,500), single object spectrograph to be mounted at the 4m NTT-ESO telescope in La Silla. The 180n/yr (for 5 years) of the SOXS Consortium guaranteed time will be dedicated to the study of transients from the ongoing and upcoming imaging surveys and space missions. Thanks to its continuous availability and to the flexible schedule maintained by the consortium, based on a remote scheduler which will interface with the observatory software infrastructure, SOXS will become one of the main follow-up instruments in the Southern hemisphere for the classification and characterisation of transients. SOXS has successfully passed the ESO acceptance in Europe and is now in Chile, ready to be mounted at the NTT (March 2025).

Speaker: Sergio Campana (Istituto Nazionale di Astrofisica (INAF))

firenze25_swift.pdf

11:40 ZTF and UVEX

TBD

Speaker: Prof. Mansi Kasliwal (California Institute of Technology)

12:00 Building a legacy, the Vera C Rubin, observatory LSST

TBD

Speaker: Dr Federica Bianco (Delaware Univ.)

12:20 → 12:40 Concluding remarks