Magnetars are amongst the most extreme astrophysical sources in the universe. With their high densities and magnetic field strengths, they are an ideal test case for fundamental physical processes. However, with only 29 known magnetars, the mechanisms for their gamma-ray emission is not well understood. The Fermi Gamma-ray Burst Monitor (GBM) is an ideal instrument in detecting outbursts of...
Dwarf novae are close binary systems where one of the components is a white dwarf that appears to exhibit abrupt and recurrent changes in viscosity in its accretion disk, causing material to fall towards the surface of the star with the consequent release of energy. As a result, these cataclysmic systems intermittently change brightness at different wavelengths. During outbursts, the increased...
The observation and modelling of the gamma-ray emission from molecular clouds (MCs) is currently the best tool to study Galactic cosmic rays. The highest energy that Galactic cosmic rays achieve is believed to be ∼ 10^15 eV, this is 1 PeV, that way a PeVatron is a source accelerating protons up to this energy. The quest for PeVatron sources aims to identify the astrophysical sources of...
A significant fraction of currently known gamma-ray binaries have bright optical counterparts that were classified as luminous early-type stars in objective prism catalogues compiled more than half a century ago. Representative examples of this statement include, in particular, LS I 61303, LS 5039 and also MWC 148. In previous years, we explored several of these historical catalogues by...
Recently, massive stars have been suggested as important sources of Galactic cosmic rays. These stars have intense stellar winds that can accelerate particles up to relativistic energies. It is expected that these stellar winds make a substantial contribution to the production of galactic cosmic rays, albeit less than that from supernova remnants. In 2019, the first detection of non-thermal...
Electrospheres are the environments of magnetized and rapidly rotating neutron stars acting like particle accelerators. With their central star slightly less energetic than the one of a pulsar, they do not host electron-positron pair creation processes. They consist of a low density plasma made of primary high energy particles. Even if we do not know their number, they are supposed to be...
Magnetar flares are one of the possible explanations for Fast Radio Bursts (FRBs). The first evidence for the FRB-magnetar connection was provided in April 2020, when the hard X-ray and soft gamma-ray bursts emitted by SGR 1935+2154 (detected by INTEGRAL, AGILE, Insight-HXMT, Konus-Wind) were observed to be associated with FRB emission. SGR 1935+2154 is a Soft Gamma Repeater, i.e. a source of...
This work investigates Cherenkov radiation originating from the quantum vacuum in pulsars. These compact astronomical objects, characterized by extreme magnetic fields, emit radiation as they rotate. By analyzing the vacuum polarization near the pulsar’s surface, we explore the contribution of Cherenkov radiation to the pulsar’s electromagnetic spectrum. Preliminary results, based on the...
The search of gamma-ray emission from accreting pulsars in X-ray binaries (XRBs) has been ongoing for some time. Recent marginal detections in high-mass X-ray binaries (HMXBs) have sparked renewed interest in this area. Anticipating future advances in gamma-ray telescopes like the Cherenkov Telescope Array (CTA), we investigate the expected emission above 10 GeV from XRBs using an enhanced...
Galactic cosmic rays may be accelerated up to PeV energies due to collective stellar winds surrounding stellar clusters. Further particle acceleration may occur due to supernova remnants within the wind-blown bubble. We apply a model of particle acceleration accounting for the stellar cluster wind termination shock and supernova remnant shocks to young and massive stellar clusters catalogued...
A significant fraction of the highest energy gamma-ray astrophysical sources observed are associated with Pulsar Wind Nebulae (PWNe). Given recent observations, the postulated, but unverified, hadronic component from PWNe requires renewed attention. We estimate possible ranges for the average pulsar pair production multiplicity on 29 sources in the Australia Telescope National Facility (ATNF)...
Cosmic rays (CRs) are high-energy charged particles ($10^{9} \sim 10^{20}$ eV) originating from the universe, yet their exact sources remain unknown. CRs are categorized into Galactic CRs (lower energy, $ \lesssim 10^{15}$ eV) and extragalactic CRs (highest energy, $\sim 10^{20}$ eV). As their names imply, Galactic CRs are accelerated within our Galaxy, while extragalactic CRs originate from...
Measuring pulsar spectra in the tens of GeV range is essential for constraining their high-energy emission models. However, this task is complicated by the fact that, in this energy domain, Fermi-LAT suffers from limited statistics, and the sensitivity of ground-based telescopes is restricted.
In this study, we combine data obtained with the largest H.E.S.S. telescope (CT-5) and...
Magnetic reconnection is ubiquitous in Astrophysics, from the Earth's magnetotail to the solar and black hole coronae, and becomes an effective mechanism for converting magnetic to kinetic and thermal energy in turbulent environments. We study turbulence's effect on magnetic reconnection rate via high-resolution 3D MHD simulations across an extensive parametric space. With an initial...
1ES2344+514 is a nearby HBL (Extreme high-frequency peaked) BL Lac object, located at a redshift of z=0.044. This source was discovered in VHE by the Whipple 10m telescope during a bright flare in December 1995. Following the event, few multi wavelength (MWL) campaigns have been organised to obtain a better understanding of the source. The extreme nature of the 1ES2344+514 in the X-ray band...
High-redshift ($z > 2$) blazars have spectral energy distributions whose inverse Compton peak usually lies in the MeV-GeV energy range. In particular, the AGILE satellite investigated 4C $+$71.07 and PKS 1830$-$211 triggering multi-wavelengths observations from the radio to the gamma-ray energy bands, in response to gamma-ray flares. We report on the multi-wavelength observations, discussing...
Lorentz invariance violation (LIV) in gamma rays can have multiple consequences, such as energy-dependent photon group velocity, photon instability, vacuum birefringence, and modified electromagnetic interaction. Depending on how LIV is introduced, several of these effects can occur simultaneously. Nevertheless, in experimental tests of LIV, each effect is tested separately and independently....
3C 216 is an extra-galactic radio source classified as a Compact-Steep Spectrum. The source is known to have extended radio structure on kpc scale and a blazar core on pc scale. In general high energy emission is more easily observed in blazars, whose jets are closely aligned with the line of sight. Starting from November 2022 Fermi-LAT observed an enhancement in the gamma-ray activity of 3C...
The interaction of cosmic rays with the cosmic microwave background (CMB) has been the subject of extensive research in the past 50 years or so. These studies have concentrated on the impact of such interactions on cosmic ray physics while neglecting the potential influence on the CMB itself due to its presumed minimal amplitude. However, the prospects of ultra-high-precision measurements of...
Star-forming galaxies, although low in gamma-ray luminosity, offer insights into cosmic ray processes. While gamma-ray emission in the GeV range is closely linked to their star formation rate, the origins of their higher-energy emissions remain unclear due to limited observations.
We gathered a comprehensive sample of galaxies, including those observed by Fermi-LAT in the GeV range and...
The origin of high-energy emission in blazars, a subclass of active galactic nuclei known for their variable, non-thermal emission across the electromagnetic spectrum, remains highly debated. Traditional one-zone models have struggled to explain the dynamic nature of these emissions, prompting more sophisticated approaches. The recent availability of X-ray polarization observations offers a...
Rapid flux variability over a large range of wavelengths is a well-known signature of blazar emission, with variability time scales of the order of a few days and below frequently observed at high energies.
Radiative models with varying degrees of complexity are generally successful in reproducing individual flare events or overall statistical behaviour, but the physical origin of blazar...
Two stages of non-thermal emission from relativistic jets in active galaxies can be distinguished: a low level persistent emission and a short period flaring emission. It has been recently proposed that both stages are produced in the inner (parsec scale) jet region when electrons are expected to be accelerated to TeV energies. The low level persistent emission originate in the extended,...
The reclassification of approximately 3000 gamma-ray extragalactic sources from the Fourth Fermi LAT Catalog resulted in an increased number of gamma-ray emitting Seyfert galaxies, including Narrow-Line Seyfert 1, misaligned active galactic nuclei (AGN), changing-look AGN, and several ambiguous objects (Foschini et al. 2022). To confirm or reject the new classifications and resolve the...
Long-term periodicity in Blazar light curves could be linked to the innermost zone of the complex structure of AGN, such as possible presence of binary system of supermassive black holes.
We analysed 16 years light curves of 1525 gamma-ray sources coming from the Fermi-LAT Light Curve Repository (LCR). First, we set up a periodicity analysis pipeline using Lomb-Scargle Periodogram (LSP) and...
PG 1553+113 is a high-frequency peaked BL Lac object (HBL), with redshift 0.433, detected with the current generation of IACTs (Imaging Atmospheric Cherenkov Telescopes) up to ~1 TeV. Interestingly, the continuous gamma-ray lightcurve collected by Fermi-LAT since 2008 showed a signature of a periodic modulation of 2.18 ± 0.08 years at energies above 100 MeV and 1 GeV. In addition, the source...
We present the results of a comparison between different methods to estimate the power of relativistic jets from active galactic nuclei (AGN). We selected a sample of 32 objects (21 flat-spectrum radio quasars, 7 BL Lacertae objects, 2 misaligned AGN, and 2 changing-look AGN) from the very large baseline array (VLBA) observations at 43~GHz of the Boston University blazar program. We then...
Narrow-line Seyfert 1 (NLS1) are a subset of AGN that accrete matter near or above the Eddington limit. Some of these galaxies can generate relativistic jets and emit gamma rays, as demonstrated by PMN J0948+0022, the first identified gamma-ray NLS1. In the early 2000s, its optical spectrum showed weak forbidden lines and a narrow H$\beta$ line with a Lorentzian profile, indicating turbulent...
Understanding the structure of active galactic nucleus (AGN) jets is still an open question. Relativistic magnetohydrodynamical (RMHD) simulations help study these jets' dynamics and emission. Recent research focuses on instabilities downstream of recollimation shocks, using 3D simulations to show their complex dynamics and effects on jet structures. Turbulence in these regions can accelerate...
Axion-like particles (ALPs) are pseudo-Nambu-Goldstone bosons predicted as an extension of the Standard Model of elementary particles, also considered as viable candidates for Dark Matter. When propagating through astronomical environments embedded with magnetic fields, very-high-energy (VHE) gamma rays may undergo conversion into ALPs, thereby altering the spectral energy distribution (SED)...
The First G-APD Cherenkov Telescope (FACT) has been monitoring blazars at TeV energies since October 2011. Within a decade of operation, it collected more than 15000 hours of physics data.
Designed for remote and automatic operation and using semiconductor photosensors, the duty cycle of the instrument is maximized and the gaps in the light curves are minimized. Thanks to the unbiased...
In the last 15 years narrow-line Seyfert 1 galaxies (NLS1) have been investigated mainly in the radio, optical, UV and X-ray energy bands. In 2008, the detection of PMN J0948+0022 by Fermi-LAT allowed us to extend their spectral energy distribution to the gamma-ray energy band, paving the way to include gamma-ray NLS1 galaxies into the class of extra-galactic jetted sources. Indeed, their...
1ES 0647+250 is a seemingly distant high-frequency-peaked BL Lac (HBL) object. Its redshift is uncertain but a recent 2023 estimate from the MAGIC Collaboration places 1ES 0647+250 at a redshift of 0.45 +/– 0.05, which is in agreement with most estimates and lower limits in the literature. A spectrum taken with the Keck Echellette Spectrograph and Imager on 2022/12/24 shows no spectral lines...
PG 1553+113 is a BL Lac object located at redshift z=0.433. It is one of the brightest and most observed extragalactic sources in the very-high-energy (VHE, E>100 GeV) gamma-ray band. One of its characteristics is the evidence of quasi-periodic modulation in high-energy (HE, >100 MeV) gamma-rays detected by Fermi-LAT, with a period of about 2.2 years.
In this contribution, we present the...
AGN jets are sprawling entities, with structures of differing size and magnetic field strength extending from very close to supermassive black holes up to over a hundred parsecs away. However, it has long been expedient to calculate their emission in one-zone models, which are effectively spheres. This is optimal for variability studies but also sidesteps the issue of irresolvable structure in...
In September 2017, the IceCube Neutrino Observatory detected a high-energy neutrino event, IceCube-170922A, associated with a gamma-ray flare from the blazar TXS 0506+056, with a probability of chance coincidence rejected at the 3σ level. This remains the most significant photon-neutrino correlation observed to date. Here, we present results from the long-term monitoring of TXS 0506+056...
X-ray observations by Chandra reveal the presence of bright spherical regions within the kilo parsec-scale jet of Centaurus A. While several models have attempted to explain such high-energy emissions at this distance, a promising scenario involves interactions between the jet and AGB stars.
I will present my recent work on jet-star interactions using 2D/3D RHD and RMHD simulations. Our...
We present a comprehensive investigation into the optical-to-X-rays properties of the gamma-ray emitting jetted Narrow-Line Seyfert 1 galaxy 1H 0323+342 ($z=0.063$). Our study spans across the years 2006 to 2023, incorporating a rich dataset with 170 $Swift$ observations in the optical, UV, and X-ray bands, integrated with $Fermi$ LAT observations from 2008 to 2023. Our key findings include...
The spectral energy distributions (SEDs) of the high energy neutrino emitted from the accretion flows are still highly uncertain, because the global structure of the accretion flow can affect the neutrino SEDs. We have calculated very high energy neutrino SEDs by using three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulations data of a magnetized accretion flow around a...
The flat-spectrum radio quasar 3C 279 is well known for its prolific emission
of rapid flares. One particular event occurred on December 20th, 2013, exhibiting
a large flux increase with a doubling time scale of a few hours, a very hard γ-ray
spectrum, and a time asymmetry with a slow decay, while no significant variations
in the optical range were detected.
We propose a novel scenario...
Fermi-LAT has accumulated continuous, high signal-to-noise, flux monitoring of bright blazars for over a decade in the gamma-ray band, measuring the dynamics of the particle acceleration and radiation zone in the blazar jet. The statistical methods often used to characterize the measured time variability, such as techniques based on the Fourier transform, rely on the underlying assumption that...
A ubiquitous feature of accreting black hole systems is their hard X-ray emission 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 hot plasma source, known as the corona, is a matter open for debate.
In this contribution we investigate the role of relativistic protons...
Featuring two peaks in the spectral energy distribution, blazars show a high variability in X-rays and very-high-energy gamma rays. A harder-when-brighter behaviour is found in many studies of the spectral index in correlation with the flux.
Within the FACT monitoring program, more than 3200 hours of physics data have been taken on the blazar Mrk 421 at TeV energies. Thanks to an unbiased...
The Spectral Energy Distribution (SED) of blazars consists of two components. The low-energy bump is interpreted as synchrotron radiation emitted by accelerated electrons while the high-energy one is produced via inverse Compton scattering of the electrons by low-energy photons. In the leptonic interpretation, the latter photon field can be provided either by the synchrotron radiation of the...
The flat spectrum radio quasar OP 313 showed extremely intense $\gamma$-ray activity from November 2023 to March 2024, as observed by the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. This initiated a large number of follow-up campaigns at all wavelengths, resulting in a confirmation of the increase of the source activity from the radio to very high energy (VHE) bands....
The origin of fast flux variability in blazars is a long-standing problem, with many theoretical models proposed to explain it. In this study, we focus on BL Lacertae to model its spectral energy distribution (SED) and broadband light curves using a diffusive shock acceleration process involving multiple mildly relativistic shocks, coupled with a time-dependent radiation transfer code. BL...
Correlations between various multiwavelength bands are an intermittent feature in blazar light curves; that is, they are observed in some instances but not in others. In order to understand the cause of this intermittency, high-cadence observations are required in as many bands as possible. In turn, correlations have been studied predominantly during flaring states. However, with the CTAO we...
I will review our recent advances in the study of the origin and development of plasma instabilities, namely Kelvin-Helmholtz and Current-Driven instabilities, at the base of quasar jets such as 3C 279, 3C 273 or 3C 111, which are variable or continuous gamma-ray emitters. We study the evolution of perturbed jets via relativistic (ideal) magnetohydrodynamical numerical simulations. An...
Although significantly fainter than the Galactic Magnetic Field (GMF), the Intergalactic Magnetic Field (IGMF) is believed to pervade the vast Cosmic voids. The IGMF was lately constrained by novel upper and lower experimental limits which motivated us to investigate the scenario in which Magnetic Monopoles (MMs) are accelerated in the IGMF and GMF. We found that IGMF acceleration demands an...
Some classes of transient sources (e.g. Novae or Kilonovae) can be at first approximation well modeled by quasi-spherical explosions in which central hot objects are surrounded by fast expanding shells. We assume that processes in the shells can turn to the acceleration of relativistic electrons which are able to comptonize soft radiation from the central object. We calculate the time...
The concomitant observation of the gravitational wave signal from a binary neutron star (BNS) merger and its electromagnetic counterparts in 2017 confirmed that these events can produce relativistic jets responsible for short Gamma-Ray Bursts (sGRBs). The complex interaction between the jet and the surrounding post-merger environment shape the angular structure of the outflow, that is then...
Fast blue optical transients (FBOTs) are extreme instances of interaction-powered supernovae which exhibit high bolometric luminosities ($\sim$ 10$^{43}$ erg s$^{-1}$) with exceptionally fast rise and decay timescales ($<$ days). Since the discovery of AT2018cow, the landmark FBOT, by the Zwicky Transient Factory (ZTF), these transients have gained increasing attention as potential particle...
Recent TeV detections of gamma-ray burst afterglows offer new insights into particle acceleration at relativistic shocks. Kinetic simulations have improved our understanding of shock microphysics, enhancing models of particle acceleration relevant to afterglows. We explore scenarios for determining the maximum achievable energy, comparing our findings with data from GRB 190829A. This...
Ultra-relativistic plasma outflows are intrinsically connected with gamma-ray bursts. Over the years, a large number of analytical and numerical works has been devoted to understanding the intricacies of their complex dynamics, with most of these past studies performed in the ideal MHD regime. We propose a self-similar formalism, based on the expansion of the equations of resistive...
The promise of multi-messenger astrophysics was clearly shown through coordinated observation campaigns of TXS 0506+056 and GW170817 in 2017. These led to the detection of a flaring gamma-ray blazar that was potentially associated with a high-energy neutrino event, and the first detection of gravitational waves from a neutron star merger by LIGO/Virgo. The multi-messenger group in VERITAS has...
Gamma-ray bursts (GRBs) exhibit a rich variety of X-ray lightcurve behaviours, including the presence or absence of plateau/shallow decay phases. There is not yet an agreed consensus about the interpretation of these findings. In this study, we analyse the properties of GRB afterglow X-ray lightcurves, focusing on two distinct populations based on their detection at high and very high energies...
The AGILE space mission, with its unique features (two coaligned imaging X-and gamma-ray detectors, a non-imaging calorimeter, and the observing capability to cover about 80 %if the sky in 7minutes) makes it very suitable in seatch for high-energy counterpar of transient of various nature. AGILE participated in all the recent campaign to search for electromagnetic (e.m.) counterparts to...
Indirect dark matter searches with gamma rays involve looking for spectral signatures that could be associated to either annihilation or decay of dark matter particles in space. In this work we present the results of a search for line-like and box-like features in the gamma-ray spectra in five sky regions centered on the Galactic Center, optimized for different DM density profiles and...
Since the detection of the binary neutron star merger (GW170817) in coincidence with the short gamma ray burst (GRB 170817A), the search for electromagnetic emission from similar events has been an imperative part of multi-messenger astronomy. The LIGO\Virgo\Kagra Collaboration (LVK) is currently in the middle of their fourth observing run (O4), which began in May 2023. Of is the most...
X-ray flares are characterized by a sudden rebrightening of X-ray radiation during the afterglow phase of gamma-ray bursts (GRBs). While the majority of GRBs exhibit a flux temporal decay consistent with the standard afterglow model, approximately one-third of GRBs observed by the Swift X-ray Telescope (XRT) display these flares. These flares, which occur primarily within a thousand seconds...
The gamma-ray burst GRB 221009A stands out as an exceptional event for its intensity, spectral evolution, and duration. We investigate the early afterglow emission of this burst, especially focusing on the unique set of simultaneous GeV-TeV spectral and intensity data obtained by AGILE and LHAASO.
We present the results of a relativistic fireball model with a set of physical parameters that...
The measurement of the flux of cosmic rays in the past could give some important information about the sources of cosmic rays, the evolution of the neighbourhood of the Solar System in the Galaxy, and the Galaxy itself. It could also inform our understanding of key events in the Earth’s history such as mass extinctions.
The paleo-detector technique consists of looking for damages inside of...
We study the supersymmetric Q balls which decay at present and find that they create a distinctive spectrum of gamma rays at around O(10) MeV. The charge of the Q ball is lepton numbers in order for the lifetime to be as long as the present age of the universe, and the main decay products are light leptons. However, as the charge of the Q ball decreases, the decay channel into pions becomes...
Gamma-ray counterparts to astrophysical neutrino sources is a topic of big interest, being the contemporary observation of both these messengers a smoking gun for cosmic-ray production.
The Cherenkov Telescope Array Observatory (CTAO) will be the next major observatory in the Very High Energy gamma-ray band. Based on the imaging atmospheric Cherenkov technique, it will reach unprecedented...
Prompt emission of GRB is believed to be produced from electrons accelerated up to non thermal energies in the internal shocks. This emission peaks in the keV-MeV energy band, but a high energy (HE; 0.1-100 GeV) component is theoretically expected. While photons in the very high energy (VHE; E>20GeV) domain have been detected by Imaging Atmospheric Cherenkov Telescopes in recent years,...
Instruments such as the ROTSE, TORTORA, Pi of the Sky, MASTER-net, and others have recorded single-band optical flux measurements of gamma-ray bursts starting as early as ∼ 10 seconds after gamma-ray trigger. The earliest measurements of optical spectral shape have been made only much later, typically on hour time scales, never starting less than a minute after trigger, until now. We designed...
The recent detections of Very High Energy (VHE) emission from GRB afterglows by the MAGIC and H.E.S.S. telescopes has opened new prospects for observing these energetic transients. Just before these detections, the seminal event GRB170817A, associated with the gravitational wave (GW) signal from a binary neutron star (BNS) merger, marked a new era in multi-messenger astronomy, providing...
The 9.7m aperture Schwarzschild-Couder Telescope (SCT) is being developed as an alternative advanced design of the medium-sized telescope for the Cherenkov Telescope Array Observatory (CTAO), which covers the CTAO’s core energy range, from about 150 GeV to 5 TeV. The novel aplanatic dual-mirror optics of the SCT makes it possible to simultaneously achieve a wide 8-degree field of view and...
In this work, it is demonstrated the potential of modern and future air shower arrays with water-Cherenkov stations for detecting upward-going neutrino events from tens of GeV to hundreds of TeV. The detection methodology employs a novel machine learning-based analysis of the signal time traces of individual stations with multiple photosensors. This enables the reconstruction of the neutrino's...
Gamma-ray astrophysics increasingly focuses on time-domain studies of variable sources like GRBs and AGNs. As the foundation for CTAO's science analysis tools, the open Python analysis library Gammapy must adapt to support these advancements. This contribution highlights the recent expansion of Gammapy's time-domain capabilities and outlines its near-future plans, particularly regarding power...
We present preliminary results on likely associations between the latest Fermi catalogue (4FGL DR3) and all INTEGRAL surveys.
The cross correlation analysis (up to a distance of 3 arcmin) finds ~90 associations of which 5+/-2 could be by chance and thus false.
Some interesting findings emerge from the analysis:
1) on the Galactic Plane we find ~20 associations where the emission is likely...
ALPACA (Andes Large-area PArticle detector for Cosmic-ray physics and Astronomy) is a new air shower array observatory to be constructed in Mt. Chacaltaya, Bolivia in 2025. The experiment will mainly be dedicated to the search for Galactic PeVatrons in the yet-unexplored southern sky through the observation of sub-PeV gamma rays. The observatory consists of two parts: a surface air shower...
Identifying extended degree-scale $\gamma$-ray structures is a challenging task for imaging atmosperic cherenkov telescopes (IACTs). This is primarily due to their comparatively small field-of-view (FOV) of around 3.5° - 5°, and a large background induced by cosmic-rays. In order to estimate this background, many approaches depend on the existence of a $\gamma$-ray free region in each...
We developed deep learning enhancements for the real-time analysis of Cherenkov telescopes data, applicable to the context of the Cherenkov Telescope Array Observatory (CTAO). The CTAO will have a Science Alert Generation (SAG) system tasked with real-time reconstruction and analysis of data, as part of the Array Control and Data Acquisition (ACADA) system. We developed two applications of...
In addition to capturing the Cherenkov signal triggered by extensive atmospheric showers, cameras from imaging atmospheric Cherenkov telescopes are also subject to signals from the night sky background and electronic noise. Image cleaning methods are employed to eliminate noise-contaminated pixels which do not have information regarding the shower. If not effectively removed, these noisy...
The ASTRI Mini-Array is an international project led by the Italian National Institute for Astrophysics (INAF) aimed at operating an array of nine small-sized (4-m diameter) Imaging Atmospheric Cherenkov Telescopes (IACTs). This array will conduct extensive galactic and extragalactic gamma-ray sky observations in the 1–200 TeV energy band, and it will be located at the Observatorio del Teide...
The array layout design of an ultra-high-energy gamma rays water Cherenkov detector represents a big challenge at the time to reach a sensitivity in the PeV energy scale. This is the current phase where the Southern Wide-field Gamma-ray Observatory (SWGO) collaboration is. In this work we address the array layout problem building a continuous model whose parameters are the primary particle...
The small-size single mirror telescopes, SST-1Ms, are two Cherenkov telescope prototypes developed by a consortium of Czech, Polish, and Swiss institutions. Featuring a 9.42 m² multi-segment mirror and a 5.6 m focal length, the SST-1Ms offer a broad 9-degree field of view and have proven capable of detecting gamma rays with energies starting from several hundred GeV. The innovative cameras...
At the Politecnico di Milano (campus Bovisa) we are installing a facility to test various possible sensors detecting the Cherenkov light emitted in water by the charged particles of the extensive air showers produced by ultra-high energy gamma rays (> 100 GeV), within the framework of the SWGO collaboration. We realized a metallic cylindrical tank (diameter 3.36 m, height 3.12 m) containing a...
High-energy neutrinos are generated in particularly energetic astrophysical environments. However, it is not easy to identify neutrino sources, given the low spatial resolution of the most sensitive current telescopes, such as IceCube or KM3NeT. The search for electromagnetic counterparts is therefore essential to identify the source and thus to study the physical conditions that lead to...
We describe the design and the expected performances of the X/Gamma-ray Imaging Spectrometer (XGIS), a GRBs and transients monitor being developed for the THESEUS mission now in Phase A as ESA M7 candidate. XGIS is capable of covering an unprecedented wide energy band (2 keV – 10 MeV), with imaging capabilities and location accuracy <15 arcmin up to 150 keV over a Field of View of 2 sr, a few...
For detailed studies of Pulsar Wind Nebulae (PWNe), objects that show photon emission across the entire electromagnetic spectrum, multiwavelength analyses are crucial. The comparison of especially X-ray and gamma-ray emission and their angular sizes can help us to constrain the properties of PWNe, such as their particle transport mechanism or their potential for the acceleration of hadronic...
GRBs are gigantic extragalactic explosions, known to release 10$^{51}$-10$^{54}$ ergs of isotropic energy, which outshine all radiation in the sky when they occur. GRBs are thought to arise in dissipation processes in which the energy of the relativistic jet is converted into non-thermal radiation. GRBs are unpredictable events both in time and place and one needs to search for them...
Authors: T. Mineo, D. Mollica, A.Compagnino, G.Leto, P.Bruno, G.Contino, S.Crestan, S.Iovenitti
The ASTRI Mini-Array is an INAF project devoted to study gamma-ray sources emitting at very high-energy in the TeV spectral band. It consists of an array of nine innovative Imaging Atmospheric Cherenkov Telescopes, that are an evolution of the double-mirror ASTRI-Horn telescope operating at the...
The Tibet AS𝛾 experiment, which observes gamma-ray/cosmic ray air showers above a few TeV, is located 4,300 m above sea level in Tibet, China. The experiment is composed of a surface air shower array (Tibet-III) and underground water Cherenkov muon detectors (MD).
The surface air shower array is used for reconstructing the primary particle energy and direction, while the underground muon...
This presentation introduces GammaBayes, https://github.com/lpin0002/GammaBayes, a Bayesian Python package designed for dark matter detection using the Cherenkov Telescope Array Observatory (CTAO). GammaBayes processes CTAO gamma-ray measurements alongside user-defined dark matter particle models, providing the posterior distribution for dark matter parameters such as the dark matter mass and...
The First G-APD Cherenkov Telescope (FACT) is observing gamma-ray sources at TeV energies. Thanks to its unbiased observation strategy, silicon-based photosensors and remote and automatic operation, it features ideal conditions both for monitoring and target-of-opportunity observations. This results in an unprecedented data sample of more than 15000 hours of physics data including monitoring...
Lorentz Invariance Violation (LIV) effects could be spotted by Imaging Atmospheric Cherenkov Telescopes (IACTs) by searching for energy-dependent time delays in the gamma-ray photons coming from distant and highly variable astrophysical sources. As part of its scientific program, The Cherenkov Telescope Array Observatory (CTAO) will explore problems in fundamental physics, including studying...
Diffuse gamma-ray emission is thought to be primarily produced by interactions between cosmic-ray protons and interstellar protons via hadronic processes. Therefore, it provides a valuable opportunity to obtain a comprehensive understanding of cosmic-ray distribution and the interstellar gaseous medium. We present the first analysis of the spatial distributions of GeV and TeV gamma-rays, hard...
Fukui et al. quantified the hadronic and leptonic gamma-rays in the young TeV gamma-ray shell-type supernova remnant (SNR) RX J1713.7$-$3946 (RX J1713), and demonstrated that gamma rays are a combination of hadronic and leptonic gamma-ray components with a ratio of $\sim$6:4 in gamma-ray counts $N$g. This discovery, which adopted a new methodology of multi-linear gamma-ray decomposition, was...
Astrophysics, and specifically gamma-ray astronomy, are transitioning into an era characterized by vast and complex datasets. The ability to make new discoveries depends on the efficient and accurate analysis of this data, necessitating the adoption of innovative methodologies. Deep Learning has become increasingly vital in addressing astrophysical challenges, with its application expanding...
