Astrophysique à Haute Energie

Study of accretion-ejection processes in the vicinity of black holes with SVOM and Einstein Probe

Supermassive black holes (SMBHs) located at the center of galaxies, particularly those powering luminous Active Galactic Nuclei (AGNs), and stellar-mass black holes in X-ray bright binary systems (XRBs), exhibit highly variable and often transient X-ray and gamma-ray emissions. Additionally, Tidal Disruption Events (TDEs) —which occur when a star approaches a massive black hole and is tidally disrupted— produce electromagnetic ares peaking in the UV and soft X-rays. 

Constraining Cosmic-Ray Acceleration through Multi-Messenger Model Fitting and Early CTAO Science

The origin of cosmic rays represents a major missing block in our understanding of the Universe. The main challenge we face is that, being charged, they are deviated in their journey from their natural accelerator to the Earth. There is however an indirect way to study their acceleration sites: wherever a cosmic ray is accelerated to high energies, it unavoidably interacts with its environment, leading to the production of photons and neutrinos. These by-products can travel along geodesics and can thus directly point to the loci of particle acceleration in the Universe.

Testing the energy dependence of the Cosmic-Ray gradient in the Galactic Centre

The Galactic Centre (GC) is a unique astrophysical environment dominated by extreme objects such as the supermassive black hole (SMBH) Sgr A* and three of the most massive  young star clusters in the Galaxy. Gamma-ray observations of interstellar gamma-ray emission using the High Energy Stereoscopic System (HESS) have revealed that a quasi-steady source near the GC injects energetic cosmic rays (CRs) into the surrounding region. These CRs propagate through the inner 200 parsecs (pc) of the Galaxy, creating a gradient in cosmic ray density. 

Seyfert galaxies as gamma-ray and neutrino sources

The origin of cosmic-rays remains one of the most important open questions in astrophysics. A powerful tool to study their acceleration sites are multi-messenger (photons and neutrinos) observations: wherever a cosmic-ray (a proton or an atomic nucleus) is accelerated, it interacts with its environment producing pions that then decay into photons, neutrinos and electrons.  γ and ν can escape the region and travel on geodesics to Earth, pinpointing their source in the Universe. 

Systematic Search for Energy-dependent Morphologies in TeV Gamma-ray Sources

The High Energy Stereoscopic System (H.E.S.S.) detects gamma-rays in the TeV (Tera-electron Volt ≡ 1012 eV) energy range, and has contributed significantly to our understanding of the high energy universe. A complete survey of the galaxy at the TeV energies was carried out by H.E.S.S., known as the H.E.S.S. Galactic Plane Survey (HGPS). The HGPS recorded nearly one hundred objects with various source types identified, including shell-type supernova remnants, pulsar powered nebulae (PWNe), compact X-ray binary systems, etc.
 

On the 16th and 17th of September was held in Paris the kick-off meeting for the Astrophysics Centre for Multimessenger studies in Europe – ACME. This HORIZON-INFRA-2023-SERV-01 EU-funded project coordinated by Centre national de la recherche scientifique CNRS aims to realize an ambitious coordinated European-wide optimization of the accessibility and cohesion...


Les 16 et 17 septembre s'est tenue à Paris la réunion de lancement du Astrophysics Centre for Multimessenger studies in Europe - ACME. Ce projet HORIZON-INFRA-2023-SERV-01 financé par l'UE et coordonné par le Centre national de la recherche scientifique CNRS vise à réaliser une ambitieuse optimisation coordonnée à l'échelle européenne de l'accessibilité et de la cohésion entre plusieurs infrastructures de recherche de pointe en matière d'astroparticules et d'astronomie, offrant un accès aux instruments, aux données et à l’expertise, axés sur la nouvelle science de l'astrophysique...

The SVOM satellite, the fruit of collaboration between the French space agency (CNES), the Chinese space agency (CNSA) and the Chinese Academy of Sciences (CAS), was successfully launched on Saturday June 22 from the Xichang base in China.

Le satellite SVOM, fruit d’une collaboration de l'agence spatiale française (CNES), chinoise (CNSA) et de l'académie des sciences chinoise (CAS), a été lancé avec succès samedi 22 juin depuis la base de Xichang, en Chine.
 

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