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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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.
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...
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...
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...
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...
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...
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...
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...
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,...
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...
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...
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...
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...
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...
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...
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 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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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.
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][1], an open-source,...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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,...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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)...
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,...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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,...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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...
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,...
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....
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...
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...
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...
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...
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...
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...
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...
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...
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...
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 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...
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...
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...
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....
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...
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...
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...
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...
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...
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...
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...
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...
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...
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,...
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...
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...
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,...
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...
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...
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...
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...
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...
