Moderadores
Gamma Rays: Galactic
- Giulia Brunelli (University and INAF-OAS Bologna)
Gamma Rays: Experiments
- Julian Sitarek (University of Lodz)
Gamma Rays: Experiments
- Rubén López-Coto ()
Gamma Rays: Extragalactic
- Monica Seglar-Arroyo (IFAE)
Gamma Rays: Extragalactic
- Mireia Nievas Rosillo (Instituto de Astrofisica de Canarias (IAC))
Gamma Rays: Galactic
- Paula Kornecki (IAA-CSIC)
Gamma Rays: Galactic
- Emma de Oña Wilhelmi (Deutsches Elektronen-Synchrotron DESY)
Gamma Rays: Extragalactic
- Lea Heckmann (APC Paris CNRS)
Gamma Rays: Galactic
- Stefano Menchiari (Instituto de Astrofísica de Andalucía - CSIC)
Gamma Rays: Extragalactic
- Alberto Dominguez (UCM & IPARCOS)
Gamma Rays: Methods
- David Green (CTAO)
Gamma Rays
- Judit Pérez-Romero (Center for Astrophysics and Cosmology/ University of Nova Gorica)
W51 is one of the most massive and active star-forming complexes in the Milky Way. Multiple experiments, including Fermi-LAT, MAGIC, HESS, HAWC, and most recently LHAASO, have detected gamma-ray emission associated with this region. The complex hosts two major star-forming regions, W51A and W51B, and the middle-aged supernova remnant (SNR) W51C. The latter has been associated with the...
The Gamma-Ray and Antimatter Survey (GRAMS) project is a next-generation MeV-scale gamma-ray and antimatter experiment. The detector consists of a liquid argon time projection chamber (LArTPC), the largest of its kind in an astrophysics experiment. Surrounding the LArTPC are plastic scintillator bars for charged particle time-of-flight (TOF) measurement. The LArTPC is the main detector and...
Crystal Eye is a new concept of space-based all sky monitor for the observation of 10 keV $-$ 30 MeV photons exploiting novel detection techniques. It foresees enhanced localization capability and detection power of the astrophysical short-duration outburst phenomena in an unprecedented energy range with respect to other concurrent instruments. The instrument uses the advantage of new detector...
The first LHAASO catalogue, published in 2023, reported the detection of 90 sources above 1 TeV, with angular extensions up to 2 deg. Among the unknown sources detected above 100 TeV by KM2A, 1LHAASO J0056+6346u appears as one of the most promising PeVatron candidates.
More recently, the LHAASO collaboration performed a dedicated study on the source, confirming the detection of the source down...
LHAASO reported 43 ultra-high-energy sources that are either proton or electron PeVatrons (Cao+24), and multi-wavelength data are crucial for determining particle species and the CR energy density of the source. In this project, we study the LHAASO J1912+1014u (and HESS J1912+101) region using Fermi-LAT and FUGIN CO data to investigate the “proton PeVatron” scenario. We analyzed 15 years of...
Monitoring the sky in the MeV energy range is crucial for understanding the nature of explosive events in the Universe. Since the Universe is transparent to MeV gamma rays, we can observe the most distant transient phenomena, such as gamma-ray bursts (GRBs). In 2017, there was the first joint observation of gravitational waves (GW) events from binary neutron stars and a GRB that initiated a...
The supernova remnant (SNR) W44, one of the first sources firmly established as a hadronic accelerator in the GeV regime, has been observed for over 200 hours with the H.E.S.S. telescope array. We present the results of a deep analysis of this dataset, revealing new insights into the gamma-ray emission from W44 and its interaction with the surrounding interstellar medium. In particular, we...
The identification of gamma rays in coincidence with high-energy neutrinos plays a fundamental role in multi-messenger astronomy, as such observations are essential for constraining source localization, determining source classes, and investigating emission mechanisms. The present study evaluates the prospects of Cherenkov Telescope Array Observatory (CTAO) for detecting very-high-energy (VHE)...
The Cherenkov Telescope Array Observatory (CTAO) will be the next-generation ground-based gamma-ray observatory, with two arrays in both hemispheres offering full-sky coverage and improved sensitivity over a broad energy range, from 20 GeV to 300 TeV. The standard pointing mode, where all telescopes are aligned to observe the same sky region, provides excellent performance in terms of...
Supernova remnants are discussed as the main sources for Galactic cosmic-rays. However, observational and theoretical developments in the last decade have lead to the idea that only supernova explosions in very dense circumstellar media are able to accelerate particles to the relevant energies and only in the first decades after the explosion.
The medium around massive stars tends to be highly...
Imaging Air Cherenkov Telescopes and Ground Based Arrays are the major contributors to Gamma
Ray astronomy at ground level. The Southern Wide-Field Gamma-ray Observatory (SWGO) will be a
water Cherenkov Array located in the Atacama Desert in Chile that will monitor the VHE and UHE sky.
The Naples group has proposed a multi-photomultiplier (multiPMT) detector for SWGO, based on
KM3NeT and...
The Cygnus region is one of the richest and most complex areas on the Galactic plane, known for its intense star formation and the presence of numerous very-high-energy gamma-ray sources. Among these sources, VER J2019+368 ranks as one of the brightest, exhibiting a hard spectrum and complex morphology that suggests the presence of powerful particle accelerators. First discovered by MILAGRO...
The project Probing Extreme PeVatron Sources (PEPS) aims at measuring the most energetic gamma rays from our Galaxy in the energy range between 10¹⁵eV and 5x10¹⁶ eV, opening a new energy window for multimessenger astroparticle physics. PEPS will consist of an array of 10 km² placed in the southern hemisphere, at the location of the Pierre Auger Observatory. It will be built in two phases, with...
Relativistic jets interact with multiple obstacles as they cross their host galaxies, before interacting with the interstellar or intergalactic medium at hotspots, in powerful sources, or plumes, in low power ones. We assume the possibility that a supernova explosion happens within the jet, and this may have a strong impact not only on the jet dynamics during the evolution of the supernova...
Extreme high-synchrotron peaked blazars (EHSPs), defined by
synchrotron peak frequencies exceeding 10^{17} Hz, represent a particularly elusive and energetic subclass of blazars. Their spectral properties challenge standard emission models and offer valuable constraints on particle acceleration processes in relativistic jets. In this work, we present a systematic study of 124 gamma-ray blazars...
MAGIC is a system of two 17-m Cherenkov telescopes located at the Observatorio Roque de los Muchachos on the Canary Island of La Palma, Spain. The telescopes have been in operations for two decades and during that time, the observation program evolved, adjusting to the new discoveries and ideas in astrophysics. Every year the telescopes observe a mixture of Galactic and Extragalactic targets....
In 2019, the first Large-Sized Telescope (LST-1) of the Cherenkov Telescope Array Observatory (CTAO) for the Northern Hemisphere array site started observations next to the two MAGIC telescopes at the Roque de los Muchachos Observatory in La Palma, Canary Islands. Since 2020 an increasing number of joint observations involving all three telescopes have been carried out. Joint MAGIC+LST-1...
Blazars are a sub-class of Active Galactic Nuclei (AGN) and constitute the most populous class of sources in the extragalactic very-high-energy (VHE) sky. They are characterized by stochastic variability that spans from radio to VHE gamma rays (E > 100 GeV), whose origins are still being debated. Detecting more VHE blazars at different energies and distances is crucial for a better...
The ASTRI Mini-Array is an international project led by the Italian National Institute for Astrophysics (INAF) to develop, build, and operate nine Cherenkov telescopes at the Observatorio del Teide, on the island of Tenerife. The array is planned to operate for at least 8 years, performing deep observations of Galactic and extragalactic sources in the energy range from 1 to 200 TeV. These...
Flat Spectrum Radio Quasars (FSRQs) are rarely detected at very-high-energy (VHE, E > 100 GeV) gamma rays due to their distance, soft spectra, and strong absorption from the Extragalactic Background Light (EBL). In December 2023, the Large-Sized Telescope prototype (LST-1) of the Cherenkov Telescope Array Observatory (CTAO) and the Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC)...
The discovery of radio galaxies as very high-energy (VHE, E > 100 GeV) gamma-ray emitters is one of the most significant legacy results from the current generation of Cherenkov telescopes. Contrary to the majority of TeV-detected active galactic nuclei, radio galaxies have misaligned jets (θ >10°). Thus, they offer unique views across multiple wavelengths to explore particle acceleration...
The LHAASO detection of the very high-energy (VHE) emission component from gamma-ray bursts (GRBs) up to the multi-TeV regime proved the importance of ground-based gamma-ray facilities in exploring the physics of these enigmatic objects up to the extreme energies. In recent years, significant efforts in improving the strategies for follow-up of transient events have been performed within the...
Recent Fermi-LAT observations have revealed GeV gamma-ray emission from several radio-quiet Seyfert galaxies, challenging the traditional view that powerful jets are required to produce high-energy gamma rays in active galactic nuclei (AGNs). One such object, GRS 1734-292, is a nearby Seyfert galaxy with empirically weak starburst and jet activity, yet it exhibits a significant gamma-ray...
The Southern Wide-field Gamma-ray Observatory (SWGO) will be a next generation ground array experiment probing the Southern sky in search of gamma-ray sources from the Galactic plane. The collaboration has chosen as primary site Pampa la Bola in the Atacama Astronomical Park (Chile) at 4770 m above the sea level. SWGO will detect the secondary particles through Water Cherenkov Detectors (WCD)....
Key extragalactic sources of very-high-energy (VHE) gamma rays include blazars, gamma-ray bursts (GRBs), and transient phenomena. Studying these targets provides critical insights into astrophysical processes such as black hole accretion, particle acceleration, and explosion dynamics. The Large High Altitude Air Shower Observatory (LHAASO), located in China, is a multi-purpose facility...
ALPACA is a new air shower array experiment under construction in Bolivia. Surface array with 401 scintillating counters covers an area of 82,800 m^2. Together with the underground water-Cherenkov muon detectors covering 3600 m^2 established by the Tibet ASgamma group, a high CR/gamma separation power is achieved. ALPACA realizes a wide-field gamma-ray survey at 10-1000TeV energy range for the...
To explore the largely uncharted dark matter mass range between 10 TeV and several PeV, the Dark100 experiment aims to deploy an array of six Imaging Air Cherenkov Telescopes (IACTs) optimized for detecting gamma rays at these extreme energies. These telescopes, originally developed for the Panoramic Search for Extraterrestrial Intelligence (PANOSETI), provide a scalable and cost-effective...
Blazars are among the most powerful objects in the Universe and are prime candidates for producing ultra-high-energy cosmic rays and astrophysical neutrinos. Yet, despite decades of observations across the full electromagnetic spectrum, their emission mechanisms remain elusive. In today’s multi-messenger era, combining data from different cosmic messengers with advanced modeling tools is key...
A complete understanding of compact binary coalescences requires combining gravitational wave (GW) observations with broadband electromagnetic data. The detection of GeV-TeV gamma rays will be crucial for probing the acceleration processes and environments near compact object mergers. The binary neutron star (BNS) merger GW170817 provided the first direct evidence that BNS mergers are...
We present gamma-ray observations by Major Atmospheric Gamma-Ray Imaging Cherenkov Telescope (MAGIC) and Large Sized Telescope (LST-1) of two of the most compelling gravitational-wave events detected by LIGO-Virgo-KAGRA (LVK) during Observing Run 4 (O4b). Conducted with MAGIC and LST-1 in a multi-telescope configuration, the campaign enabled a sensitive search for very-high-energy...
The prompt and early afterglow phases of gamma-ray bursts (GRBs) remain elusive, especially in the very-high-energy (VHE, E > 100 GeV) domain. While space-based instruments like Fermi/LAT have extended our view of GRB emission up to 100 GeV, the detection of the early TeV emission from GRBs remains challenging. Limitations including poor sky localization from Fermi/GBM detected GRBs,...
Gamma-ray bursts (GRBs) of long duration arise from ultra-relativistic jets that appear shortly after the collapse of massive stars. The highly variable prompt emission, lasting only a few minutes, results from internal dissipation within the jet and is followed by an afterglow that can last several days. This afterglow emission, observable at energies ranging from radio to TeV, is primarily...
The detection of Gamma-Ray Bursts (GRBs) at Very High Energy (E > 100 GeV) was a long-awaited result, and many observations were needed before achieving this goal. The study presented here is based on a complete re-analysis of 15 years of GRB observations with the High-Energy Stereoscopic System (H.E.S.S.) providing the most extensive set of VHE upper limits to date.
This study contributes to...
Gamma-ray bursts (GRBs) are among the most powerful transients in the Universe and a key science target for the MAGIC Collaboration. Despite the observational challenges inherent to Imaging Atmospheric Cherenkov Telescopes (IACTs), MAGIC has implemented a dedicated strategy for rapid follow-up of GRBs, enabling observations at a rate of ~10 GRBs per year since 2013. While two GRBs have been...
Accurate modeling of the early X-ray emission in short GRBs is essential for probing the GRB engine, understanding jet physics, and improving electromagnetic follow-up of gravitational wave signals from binary neutron star mergers in the context of multi-messenger astronomy.
Thanks to the operation of the Swift satellite over the last 20 years, we now have access to an extensive archive of...
Space-based gamma-ray observations have established sharp cutoffs at a few GeV as a common feature of pulsar emission, with the Crab pulsar until recently the only source detected above 100 GeV. Observations with imaging atmospheric Cherenkov telescopes (IACTs), such as H.E.S.S., now reveal pulsar spectra extending up to tens of TeV. For the Vela pulsar, we detect a distinct radiation...
Over the past two decades, the discovery of pulsed very-high-energy (VHE) emission of the Crab pulsar, along with the expansion of the gamma-ray pulsar catalogue driven by the Fermi-LAT satellite, has led to a paradigm shift in the understanding of the gamma-ray emission of pulsars. Once believed to originate near the neutron star’s surface, particle acceleration and radiative processes are...
Pulsar wind nebulae (PWNe) are bubbles of relativistic particle outflows, primarily composed of electrons and positrons, which are continuously injected from pulsars and often exhibit broadband non-thermal radiation originating from synchrotron and inverse Compton scattering emission. Recently, LHAASO and HAWC observations have detected Ultra-High-Energy (UHE, E>100 TeV) gamma-ray sources...
A point-like gamma-ray source (HESS J1745–290) has been detected in the inner Galactic Center, spatially coincident with Sagittarius A (Sgr A). However, the currently quiescent state of Sgr A* challenges its interpretation as the origin of the emission. An alternative explanation is that a single pulsar wind nebula (PWN) accounts for the observed signal. However, X-ray observations have...
There has been ongoing debate about the potential unconfirmed asymmetric structure of the diffuse $\gamma$-ray emission of the Geminga halo. In this work, we adhere to first principles, injecting and propagating individual cosmic ray (CR) electrons in 3D realizations of turbulent magnetic fields characterized by Kolmogorov turbulence and Bohm turbulence. The particle motion is governed by the...
Pulsar halos—extended regions of relativistic electrons surrounding middle-aged pulsars—offer critical insight into cosmic-ray acceleration and transport in the interstellar medium. These sources are often bright in the TeV gamma-ray band due to inverse Compton scattering by the most energetic electrons, which are also expected to emit synchrotron radiation in the X-ray band. A multiwavelength...
TeV “halos” discovered around Geminga and Monogem by HAWC expose pockets of severely quenched particle diffusion close to middle-aged pulsars. Resolving the properties of these slow-diffusion zones, such as the size of the slow-diffusion zone, and local magnetic field strength, is pivotal for modelling lepton transport and for assessing the pulsars’ contribution to the local positron excess....
Cygnus X-3 is a microquasar consisting of a compact object of unknown nature and a Wolf-Rayet star, which orbit each other with a very short period of 4.8 hours. The compact object launches powerful jets that are an excellent site for particle acceleration up to relativistic energies. The presence of these relativistic particles, combined with the proximity to the star and its high luminosity,...
VERITAS is one of the world’s most sensitive very-high-energy (VHE; E > 100 GeV) gamma-ray observatories. Around half of its good-weather observations were targeted on active galactic nuclei (AGN). We present the recent efforts to reprocess the historical archive of VERITAS and produce a standardized, first VERITAS TeV AGN Catalog, and announce several new detections by VERITAS of AGNs at TeV energies.
Blazars are a subclass of active galactic nuclei in which the relativistic jet-component aligns closely with the observer’s line of sight. Due to this viewing geometry, the observed emission is dominated by the highly Doppler boosted non-thermal jet emission which originates from the jet. At optical/UV wavelengths the emission is produced by leptonic synchrotron emission from relativistic...
Gamma-ray binaries are rare stellar systems where a compact object interacts with a massive companion star, producing high-energy emission in the MeV–TeV range. Leveraging the sensitivity of LHAASO’s WCDA and KM2A detectors, we analyze multiple key systems, including HESS J0632+057, PSR J2032+4127, GRS 1915+105, SS 433, LS 5039, and LS I +61 303. These sources display diverse behaviors such as...
We explore the high-energy emission of cosmic messengers from galaxy clusters hosting active galactic nuclei (AGNs) such as Perseus. The main objective is to distinguish the emission from the central source, such as NGC $1275$, from the diffuse emission. Due to high magnetic field and large size of clusters, CRs with energy $\leq 10^{18}$ eV can be confined within these structures over...
Gamma-ray binaries are among the most extreme accelerators in the Galaxy, capable of producing photons at TeV energies. LS 5039, a well-studied high-mass X-ray binary, is one of the few systems known to emit modulated TeV gamma rays. We report the detection of orbital modulation in gamma rays from LS 5039 up to 100 TeV using over 2800 days of observations with the High-Altitude Water Cherenkov...
The binary system Eta Carinae is a unique laboratory to study particle acceleration processes under a wide range of conditions. Particles are thought to be accelerated at shocks forming in the wind collision region. Eta Carinae has been firmly established as a source of high-energy (HE) and very-high-energy (VHE) gamma-rays in Fermi-LAT and H.E.S.S. data in the last decade. With its highly...
Active galactic nuclei (AGNs) are powered by accretion onto supermassive black holes (SMBHs), yet the mechanisms governing their energy output and the growth of SMBHs, particularly at high redshift, remain incompletely understood. Blazars, a subclass of AGNs with relativistic jets oriented close to our line of sight, are detectable across the electromagnetic spectrum, from radio to gamma rays,...
Gamma-ray binaries produce the majority of their multi-wavelength non-thermal emission at energies >1 MeV. These systems consist of an O/Be star and a compact object, which has been detected as a neutron star in 3 of the 9 systems. It is largely understood, then, that the VHE non-thermal emission in these systems originates in a stand-off shock that is produced when the stellar wind and/or...
Blazars show variability across the entire electromagnetic spectrum and over a wide range of timescales. In some cases, characteristic emission patterns have been observed, such as the multi-year modulation detected in PG 1553+113. Quasi-periodic oscillations (QPOs) can arise from various astrophysical mechanisms, including jet precession, accretion disk instabilities, and supermassive binary...
At the edge of the Galactic supernova remnant (SNR) Vela Junior lies the pulsar PSR J0855-4644. Pulsars are among the most efficient particle accelerators in our Galaxy, making the study of this region of interest. PSR J0855-4644 has remarkable X-ray and radio features, revealing a pulsar wind nebula (PWN) structure along with a bow shock nebula. PSR J0855–4644 stands out as one of the highest...
Spinning super-massive black holes at the centers of galaxies can launch powerful magnetized jets. 3C 279 is an archetypal blazar with a prominent radio jet that undergoes broadband emission variability. In April 2017 and April 2018, the Event Horizon Telescope (EHT) observed 3C 279 with an unprecedented angular resolution of 20 micro-arcseconds. In parallel, an extensive quasi-simultaneous...
Radio-loud Active Galactic Nuclei (AGN) produce relativistic jets that are among the most energetic structures in the universe. These jets emit radiation across most of the electromagnetic spectrum, with their Spectral Energy Distribution (SED) typically exhibiting a double hump structure. The lower energy part of the SED is dominated by synchrotron emission from non-thermal electrons in the...
Majority of supernova remnants expand into a complex environment of the stellar wind bubble blown up either by their progenitor or their companion star, where forward shock might interact with various density inhomogeneities. Such interactions would cause formation of fast reflected shocks propagating back and forth between the forward shock, the contact discontinuity in the interior of the...
On 2 July 2025, the Gamma-ray Burst Monitor (GBM) onboard the Fermi Gamma-ray Space Telescope detected three short-duration MeV transients with overlapping sky locations. These events, named GRB 250702D/B/E (DBE), were triggered within approximately 1-2 hours of one another. Follow-up observations of this unusually long MeV transient (lasting longer than 3 hours) by the Neil Gehrels Swift...
PG 1553+113 is a BL Lac object located at redshift z = 0.433. It is one of the most luminous extragalactic sources in the very-high-energy (VHE, E > 100 GeV) gamma-ray band, and it has been detected by all currently operating Imaging Air Cherenkov Telescopes (IACTs). A key feature of this source is the evidence of quasi-periodic modulation in high-energy (HE, E > 100 MeV) gamma rays detected...
PG 1553+113 is a high-frequency peaked BL Lac object with a redshift of 0.433, detected by the current generation of Imaging Atmospheric Cherenkov Telescopes up to approximately 1 TeV. Interestingly, the continuous gamma-ray light curve recorded by Fermi-LAT since 2008 has shown a periodic modulation of 2.18 ± 0.08 years at energies above 100 MeV and 1 GeV. Additionally, the source shows clear...
Cygnus is a vast star-forming complex harbouring a population of powerful objects, including massive star clusters and associations, Wolf-Rayet stars, pulsars, and supernova remnants. The multi-wavelength picture is far from understood, in particular the recent LHAASO detection of multi-degree scale diffuse γ-ray emission up to PeV energies. In this talk, I demonstrate that hadronic emission...
Massive young stellar objects (MYSOs) can drive high-speed, collimated outflows capable of propagating at hundreds of kilometers per second through the circumstellar medium. The strong shocks produced in the internal regions of these jets, as well as the powerful termination shocks, can create favorable conditions for particle acceleration. In this study, that has been published in the...
We present the first gamma-ray study of X-ray selected AGN in dwarf galaxies, using 15 years of Fermi-LAT data. These low-mass systems likely host intermediate-mass black holes and offer a unique view into accretion and feedback in the faintest galactic nuclei, as well as a new window into the properties of dark matter. While no individual source is detected, a joint likelihood analysis of 74...
Markarian 501 is a well know close by (redshift = 0.034) BL Lac object. It is categorized as a high-synchrotron peaked blazar (HSP; νpeak> 10^{16} Hz) with temporarily extremely high-synchrotron peaked behavior (EHSP; νpeak> 10^{17} Hz). The proximity of the source allows for the observations in the Very High Energy range (VHE; E> 100 GeV) by IACTs, such as the MAGIC telescopes. In 2014, the...
In recent years, massive star cluster environments have emerged as a new class of gamma-ray sources capable of accelerating particles to very-high energies, to such extent that they could complement the supernova model for the origin of galactic cosmic rays. The environment sculpted by the interaction of powerful stellar winds is complex, highly structured from small (pc) to large (100 pc)...
M87* is a particularly well-studied black-hole system, thanks to the wealth of spectral data and the ability to image its central region using VLBI techniques. We present a model of the broadband emission of this object, in which radiation from the millimetre to TeV range is explained by leptonic emission from the innermost accretion flow. The model is based on GRMHD simulations and takes into...
Star-forming galaxies (SFGs) provide a unique laboratory to investigate cosmic-ray (CR) acceleration and transport in environments shaped by massive stellar populations. Their non-thermal emission, including γ-rays, is primarily associated with star formation rather than active galactic nuclei, as evidenced by the well-established correlation between star formation rate (SFR) and both radio...
LHAASO has recently detected ultra-high-energy (UHE, >100 TeV) γ-rays from various Galactic sources, including supernova remnants, pulsar wind nebulae, microquasars, and young massive clusters. The presence of these UHE γ-rays indicates the potential acceleration of cosmic rays to PeV energies. A leading explanation for this emission involves CRs from sources interacting with nearby molecular...
Galaxy clusters are the most massive gravitationally bound structures in the Universe. Even if clusters are nearly virialized structures, they undergo merging processes, creating merging shocks, and suffer from feedback from galaxies and AGNs; causing complex turbulent motions and amplifying their magnetic fields. These processes act as acceleration mechanisms for the plasma of the...
In 2010, the Fermi Gamma-ray Space Telescope observed two gamma-ray emitting structures, the Fermi Bubbles (FBs), that extend up to 55° above and below the Galactic plane and that seem to emanate from the Galactic center region. Although the spectrum at latitudes |b| > 10° has a softening or a cutoff around 100 GeV, the one at the base of the FBs, |b| <10°, extends up to about 1 TeV without a...
NGC 4278 is a low-luminosity active galactic nucleus (AGN) in the local Universe. The detection of very-high-energy (VHE) gamma rays from NGC 4278 by the Large High Altitude Air Shower Observatory (LHAASO) has identified it as a newly discovered extragalactic TeV gamma-ray source. However, the physical origin of the VHE gamma-ray emission from NGC 4278 remains unclear.
In this study, we...
The extragalactic background (EGB) observed by Fermi-LAT provides a detailed map of the non-thermal universe. We construct a simulation-based inference framework with the goal of characterizing the full information contained in the EGB. Using a convolutional neural network method, we provide the first simultaneous inference of the energy spectrum and source-count distribution (SCD) for the...
About half of the Fermi-LAT gamma-ray sources within plus or minus 10 degrees in latitude from the Galactic plane are unassociated. Interestingly, the distribution of the Galactic unassociated sources as a function of spectral parameters is different from the distributions of known classes of Galactic sources, such as pulsars, supernova remnants, and pulsar wind nebulae. This difference in...
Galactic cosmic-ray accelerators are identified efficiently by gamma-ray observations of space-borne and ground-based instruments. The gamma-ray sources observed so far, however, represent only the tip of the iceberg, a highly biased sample of the brightest and closest sources. Studying the population as a whole requires careful evaluation of the available data and their biases, stemming from...
The analysis generally applied to Imaging Atmospheric Cherenkov Telescopes data optimizes quality selection cuts, selecting a sub-sample of high-quality events, and computes a set of Instrument Response Functions (IRFs) for these events. All surviving events are treated as equal in quality, and are assumed to be well represented by a single set of IRFs, while the rest of the events are...
The Cherenkov Telescope Array Observatory (CTAO) will be the next generation of very high energy (VHE) gamma-ray observatories, using Imaging Atmospheric Cherenkov Telescopes (IACTs) such as the LST-1 (Large-Sized-Telescope-1). In this contribution, we present a successful application of deep learning techniques for event reconstruction in real LST-1 data, using the CTLearn framework. The...
The Cherenkov Telescope Array Observatory (CTAO) marks the next generation of Imaging Atmospheric Cherenkov Telescopes (IACTs), offering a sensitivity increase of up to five to ten times over current instruments. Its first prototype, the Large-Sized Telescope (LST-1), is already in operation at the Roque de los Muchachos Observatory in La Palma, Spain. Deep learning methods have shown...
Graph Neural Networks (GNNs) have emerged as a robust architectural choice for deep learning across scientific disciplines, and are particularly suited for datasets with irregular topology. The MAGIC Telescope, comprising a pair of 17 m Imaging Atmospheric Cherenkov Telescopes (IACTs) located at Roque de Los Muchachos Observatory in La Palma, Spain, is designed to detect gamma rays from around...
The Cherenkov Telescope Array Observatory (CTAO) will be the world's first gamma-ray observatory with majority of observation time in the first 10 years driven by open proposals. Designed to operate for 30 years, with two sites, the Northern site at the Observatorio Roque de los Muchachos and the Southern site at the ESO Observatorio Paranal, CTAO will cover the entire sky with unprecedented...
Core-collapse supernovae (CCSNe) are explosive astrophysical events that emit radiation across the entire electromagnetic spectrum, extending up to soft gamma rays. Very high-energy (VHE; E > 100 GeV) gamma-ray emission is expected to arise from shock interactions between dense circumstellar material and the supernova ejecta. However, no unambiguous detection has yet been achieved by past or...
Models predict that the Sun can produce bright gamma-ray emission through two separate mechanisms. First, ambient cosmic-ray protons can undergo hadronic interactions with the solar atmosphere producing a bright flux across the solar disk. Second, cosmic-ray electrons can inverse-Compton scatter ambient sunlight to gamma-ray energies.
Observations by the Fermi-LAT and HAWC telescope have...
Relativistic pair beams formed in the intergalactic medium (IGM) by TeV gamma rays from blazars are expected to generate a detectable electromagnetic cascade in the GeV range. However, this cascade is notably absent in the spectra of many hard-spectrum TeV blazars. One common explanation is that weak intergalactic magnetic fields deflect the resulting electron-positron pairs out of our line of...
We investigate the effects of Lorentz invariance violation (LIV) on photon interactions, considering both intergalactic propagation (Breit-Wheeler process) and atmospheric interactions (Bethe-Heitler process). By incorporating LIV into the theoretical framework, we analyze how it modifies key quantities such as the cross section, threshold energy, and mean free path of photons traveling...
Lorentz invariance violation (LIV) is a speculated consequence of some models of quantum gravity. It is modelled as a modified dispersion relation of massless particles. One direct effect of LIV is energy-dependent photon group velocity. This hypothesis is tested by measuring time delays in the arrival of high-energy photons from astrophysical sources. Suitable targets are variable, distant...
The Large Magellanic Cloud (LMC) is a satellite galaxy, orbiting the Milky Way at a distance of approximately $50 \text{kpc}$. This galactic neighbour contains some of the most luminous TeV gamma-ray sources; namely N$~$157B, the first extra-galactic pulsar wind nebula detected, the supernova remnant N$~$132D, the young massive stellar clusters 30$~$Dor$~$C and R$~$136, and the gamma-ray...
