Conveners
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- Andrea De Luca (Istituto Nazionale di Astrofisica (INAF))
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- Patrizia Caraveo (Istituto Nazionale di Astrofisica (INAF))
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- Josep Maria Paredes (Universitat de Barcelona)
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- Andrea Giuliani (Istituto Nazionale di Astrofisica (INAF))
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- Alison Mitchell (Erlangen Centre for Astroparticle Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg)
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- Josep Martí (Univesity of Jaén)
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- Julian Sitarek (University of Lodz)
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- There are no conveners in this block
Recent measurements revealed the presence of several features in the cosmic ray spectrum. In particular, the proton and helium spectra exhibit a spectral hardening at ~ 300 GV and a spectral steeping at ~ 15 TV, followed by the well known knee-like feature at ~ 3 PV. The spectra of heavier nuclei also harden at ~ 300 GV, while no claim can be currently done about the presence of the ~15 TV...
The Galactic center region is one of the richest in the Milky Way, hosting a large variety of sources such as supernova remnants, pulsar wind nebulae and stellar clusters. The supermassive black hole Sgr A* is surrounded by dense molecular cloud complexes that shape the so-called central molecular zone (CMZ). Very-high-energy gamma-ray emission has been reported towards this inner 200 pc...
Most known Galactic supernova remnants do not appear to contribute significantly to the cosmic-ray (CR) flux at PeV energies at their current evolutionary stage. However, supernovae (SNe) could still be major contributors to the “knee” of the CR spectrum if their shocks are efficient hadronic accelerators at earlier times – within days or weeks after the collapse of their progenitor's core....
Cosmic rays (CRs) interact with turbulent magnetic fields in the interstellar medium (ISM), generating non-thermal emission. After many decades of studies, the theoretical understanding of their diffusion in the ISM continues to pose a challenge. This study numerically explores a recent prediction termed "mirror diffusion” and its synergy with traditional diffusion mechanism based on ...
Cosmic rays (CRs) in the GeV-PeV range are believed to originate mainly from sources in the Milky Way (MW) disk, propagate diffusively in the interstellar medium, and eventually escape into the circumgalactic medium (CGM) that permeates the MW halo. Circumgalactic CRs (CGCRs) may play important thermal and dynamical roles for the formation and evolution of the MW, but observational evidence...
Gamma-ray observations provide important information on cosmic-ray (CR) propagation in our Galaxy.
First, we discuss detected TeV halos. We show that current gamma-ray measurements place interesting constraints on the turbulent magnetic fields around these pulsars, and we examine the implications for CR transport. Also, we suggest that extended gamma-ray sources of a hadronic origin should...
The Milky Way, with its distinctive observational features, is a unique laboratory to constrain physical parameters and test various theories of galaxy evolution ranging from star formation, to the formation of gaseous structures and galactic outflows, such as the Fermi and eRosita bubbles. A particularly important ingredient in the interstellar medium are cosmic rays (CRs), which reveal their...
The center of our Milky Way galaxy hosts a series of energetic outbursts, including the well-known Fermi and eROSITA bubbles, Galactic center chimneys, the inner 15-pc Sgr A lobes. Are they long-lasting or fast evolving explosive events? What causes these structures? Are they PeVatrons related to ultra high energy gamma ray emissions from the central molecular zone and the Galactic center? The...
The large-scale structures such as Fermi Bubbles and eROSITA Bubbles provide a unique opportunity to study our Milky Way. However, the nature and origin of these large structures are still under debate. In this talk, I will present the identification of several kpc-scale magnetised structures based on their polarized radio emission and their gamma-ray counterparts, which can be interpreted as...
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...
Our Galaxy is known to be a strong source of gamma-ray emission. Besides the active objects liable for the persistent and variable high and very-high energy photons, the interplay between the interstellar matter and cosmic rays is of crucial relevance, as it assumes the role of a passive source of gamma rays. Indeed, the collisions of extremely energetic charged particles with the gaseous...
The Galactic Centre (GC) is a complex region with several sources emitting very-high and ultra-high energy photons. It is also a unique place for Dark Matter (DM) searches under the assumption of cuspi profile in the WIMP theory. The Southern Wide field-of-view Gamma-ray Observatory (SWGO) is currently under development aiming to observe the GC region among other interesting regions in the...
Three pulsars, namely Crab, Vela and Geminga, have been detected in gamma rays above 20 GeV using Imaging Cherenkov Atmospheric Telescopes (IACT). Detecting new very-high-energy (VHE) pulsars is challenging due to the limited sensitivity of the current IACTs. The Cherenkov Telescope Array Observatory (CTAO) will be the next generation of Cherenkov telescopes, comprised of dozens of telescopes...
The Crab, Geminga and Vela pulsars are among the brightest gamma-ray pulsars detected so far. Fermi-LAT observations revealed that each of these three pulsars has its GeV pulse profile consisting of two peaks and a bridge between them. There are a number of candidate emission regions in a pulsar magnetosphere, and various leptonic mechanisms were proposed to explain pulsars’ gamma-ray...
Recent very-high energy (VHE) observational studies have indicated the presence of the so-called TeV halos around several nearby middle-aged pulsars. Follow-up theoretical studies point out the possible general existence of the TeV halos, although under debate. If they generally exist as suggested, they would contribute significantly to cosmic positrons/electrons in our Galaxy. The full...
In this talk I will present the current status of our development of an effective radiative model versatile enough to be applied to hundreds of
pulsars. The model follows the dynamics of charged particles being accelerated in the magnetosphere of a pulsar and computes their emission via synchro-curvature radiation, with only three free effective parameters involved. The model has succeeded in...
We report on the discovery of multi-TeV gamma-ray pulsationsfrom PSR J1509-5850 with the H.E.S.S. array of imaging atmospheric Cherenkov telescopes. The light curve above 500 GeV is similar to the one obtained in the multi-GeV range with Fermi-LAT with no significant evolution with increasing energy.
The pulsed spectrum, as measured in the 500 GeV-10 TeV range, displays a hard index and is...
‘Spider’ binary systems – black widow and redback compact binaries differentiated by their companion’s mass and nature – are an important type of pulsar system exhibiting a rich empirical phenomenology, including radio eclipses, optical light curves from the heated companion, as well as non-thermal X-ray and GeV light curves and spectra. Multi-wavelength observations have now resulted in the...
Pulsars are the main population of gamma-ray emitters in the Galaxy. To date, the Fermi Large Area Telescope (LAT) has detected about 300 gamma-ray pulsars, some young and energetic and others belonging to the family of older and fast-rotating millisecond pulsars. Because of their much broader gamma-ray beams, a significant number of LAT pulsars discovered in gamma rays are undetectable in...
Radio pulsars are quintessential high-energy astrophysics objects. They emit most of
their energy in gamma-rays, accelerate particles to very high energies and produce
dense relativistic plasma. Despite decades-long efforts, we still do not have a
consistent model of radio pulsars, though significant progress has been achieved in
the last two decades thanks to advances in numerical models...
We report the first observational evidence for magnetic field amplification in the north-east/south-west (NE/SW) shells of supernova remnant SN 1006. SN1006 is one of the most promising sites of the production of galactic cosmic ray (CRs) through diffusive shock acceleration (DSA), although the detailed process of DSA is not well understood. Particularly, the magnetic field strength and...
G284.3$-$1.8, also known as MSH 10-53, is a supernova remnant (SNR) with a radio shell (e.g., Milne et al. 1989) and thermal X-ray emission (e.g., Williams et al. 2015). Near the center of the SNR is the gamma-ray binary 1FGL J1018.6$-$5856, which was discovered in high-energy gamma rays by the Fermi Large Area Telescope (Fermi LAT Collaboration 2012). Follow-up observations found X-ray...
Wide field-of-view survey instruments with good sensitivity at the highest energies have recently revealed an unexpectedly large population of galactic gamma-ray sources reaching ultra-high-energies (>100 TeV). Several of these have no known counterpart accelerator. However, the highest energy cosmic rays accelerated by supernova remnants will escape from the shock region at early times in the...
In recent years the number of known sources emitting in the TeV-PeV regime has increased significantly thanks to facilities like LHAASO and HAWC. These observations could change our understanding of high-energy processes in our Galaxy. However, many of the observed sources are still unidentified or poorly constrained due to the limited angular resolution of these instruments, and most of the...
The quest for PeVatrons, sources of galactic cosmic rays accelerated up to PeV energies, has lived exciting developments in the last years, thanks to the many gamma-ray sources detected by ground array experiments at energies above 100 TeV. Among these, the supernova remnant SNR G106.3+2.7 appears to be one of the most promising hadronic PeVatron candidates, for which the ultra-high energy...
Investigating the molecular clouds surrounding a supernova remnant (SNR) is essential in understanding the acceleration and diffusion processes of cosmic rays because the clouds act as targets for cosmic-ray protons to produce gamma-rays via the hadronic processes. We present new observations of TeV gamma-ray SNR W28 with the Atacama Large Millimeter/submillimeter Array (ALMA) in $^{12}$CO(J...
Observation with an arc-minute scale resolution of dense molecular clouds located at pulsar-wind nebulae (PWNe) is important to study the interaction between the interstellar gas and PWN and the evolution of the complex morphology of PWNe, as noted in some previous literature. Our study performs the first dedicated research of the molecular clouds located at Vela X, the large PWN around the...
RS Ophiuchi is a recurrent nova which explodes on average every 15 years. These explosions result in nova shocks from which non-thermal particles and radiation are produced. In fact, the most recent outburst of RS Ophiuchi in 2021 has been observed by a few different gamma-ray instruments including FERMI-LAT, HESS and MAGIC. Interestingly, the highest TeV gamma rays are only detected about two...
Two recent classical novae, V1723 Sco (2024) and V6598 Sgr (2023), were detected by the Fermi-LAT. V1723 Sco is one of the brightest novae observed to date by the LAT, providing a two-week window for detection. The extensive Fermi observations of V1723 Sco, complemented by a rich multi-wavelength dataset including NuSTAR and VLA, enable precise constraints on various parameters of the emission...
The number of young star clusters identified as sources of gamma-ray emission has been increasing in recent years, hinting at ongoing particle acceleration within these regions. The interaction between winds from massive stars can create collective shocks and lead to the formation of superbubbles (SBs), whose interior is filled with tenuous, hot, turbulent plasma. Characterising these...
Young massive stellar clusters have recently brought attention as PeVatrons candidates, to explain the knee of the cosmic ray spectrum and how protons can be accelerated to such energy scale in galactic sources. Since direct verification is not possible because of the diffusion of cosmic rays in the interstellar medium, one can use photons that are produced when cosmic rays interact with...
PeVatrons constitute a fascinating class of astrophysical objects capable of accelerating particles up to PeV energies (1 PeV = 1015 eV). However, their nature and their acceleration mechanisms are still uncertain. The accelerated particles interact with the surrounding interstellar medium and background radiation fields to produce secondary ultra-high-energy gamma rays (>100 TeV), which are...
Young massive stellar clusters (YMSCs) have emerged as a potential
gamma-ray sources, after the recent association of several YMSCs with extended gamma-ray emission. The large size of the detected halos, comparable to that of the wind-blown bubble expected around YMSCs, makes the detection of individual YMSCs rather challenging. As a result, the gamma-ray emission from most of the Galactic...
Massive Star Clusters (SCs) have been proposed as additional contributors to Galactic Cosmic rays (CRs), to overcome the limitations of supernova remnants (SNR) to reach the highest energy end of the CR spectrum. Thanks to fast mass losses due to the collective stellar winds, the environment around SCs is potentially suitable for particle acceleration up to PeV energies and the energetics is...
The Cygnus X region has become a source of great interest since its detection in gamma-rays by Fermi, HAWC and recently LHAASO, the latter having measured photon energies above 1 PeV. This likely indicates the presence of a hadronic source of PeV cosmic rays in the region, although the accelerator has not been yet identified. The emission is coincident with the stellar association Cygnus OB2,...
We present the observational capabilities of the ASTRI mini-array, an array of nine small-sized Cherenkov telescopes deployed at the Teide Observatory (Tenerife, Spain), by focusing on the state of the art of TeV emitting sources in the Cygnus region (along the 60-80 longitudinal range of the Galactic plane). This is currently the richest known region of Galactic sources emitting above 1 TeV,...
Recent gamma-ray observations detect photons up to energies of a few PeV. These highly energetic gamma rays are emitted by the most powerful sources in our galaxy. Propagating over astrophysical distances, gamma rays might interact with background photons producing electron-positron pairs, then deflected by astrophysical magnetic fields. In turn, these charged particles might scatter through...
In high energy Gamma-Ray Astronomy with shower arrays the most discriminating signature of the photon-induced showers against hadron-induced cosmic-ray ones is the content of muons in the observed events.
In the electromagnetic $\gamma$-showers the muon production is due to the dominant channels: photo-production of pions followed by the decay $\pi\to\mu\nu$, prompt leptonic decay of charmed...
Detection of gamma rays and cosmic rays from the annihilation or decay of dark matter particles is a promising method for identifying dark matter, understanding its intrinsic properties, and mapping its distribution in the universe. I will review rthe current status and discuss the prospects for indirect searches to robustly identify or exclude a dark matter signal using upcoming experiments...
In the recent (sub-)PeV gamma-ray astronomy, we can pinpoint locations of Galactic PeV cosmic-ray accelerators, known as PeVatrons, as LHAASO has detected 43 sources with E>100 TeV. Such ultra-high-energy (UHE) photons likely originate from protons, since the Klein-Nishina effect would suppress leptonic gamma-ray emission. Some of these UHE sources are poorly explored in other wavelengths,...
The first LHAASO catalogue has provided many new VHE/UHE sources and potentially new classes of sources that are primed for exploration with IACTs. The improved sensitivity at low energies ( E < ~1 TeV) and angular resolution of IACTs make them the ideal instruments to help associate and perform spectro-morphological studies of these newly discovered sources. Most of these sources...
The unassociated population represents about 30% of the sources in the latest 4FGL-DR4 release, with about one half lying at low (|b|<10°) Galactic latitudes. Many of these low-latitude sources exhibit properties that set them apart from established classes of Galactic gamma-ray emitters, in particular very soft spectra. The latter feature earned them the denomination "soft Galactic...
Microquasars present a remarkable opportunity to study particle acceleration in astrophysical jets due to their relative proximity to Earth compared to their extra-galactic counterparts. Yet this opportunity is rather limited since TeV emission has only been firmly associated with the jets of one microquasar so far. Fortunately, this might be about to change: in this contribution we present...
Very recently, gamma-ray emission detected by Fermi-LAT was reported from a star forming region NGC 2071. The high-energy radiation was claimed to be associated with occasional mega-flares thought to occur in T Tauri stars. The source, detected at energies $E \sim 100$\,GeV, appears to be transient, and was only detectable during the first two years of observation. In this work, we...
