The origin of very- and ultra-high-energy cosmic rays remains one fundamental question in astroparticle physics. High-energy neutrinos would provide a distinct signature for acceleration processes in galactic and extragalactic sources.
Les systèmes binaires X sont constitués d’un objet compact, étoile à neutrons ou trou noir, en interaction avec une étoile compagnon. Sous l’effet du fort potentiel gravitationnel de l’objet compact, une partie de la matière de l’étoile compagnon est accrétée par l’objet compact. Cette matière forme un disque d’accrétion qui, en se réchauffant par friction, émet un rayonnement intense dans le domaine des rayons X.
The Astroparticle physics groups hosted at the Centre for Cosmology, Particle Physics and Phenomenology (CP3) at UCLouvain (Belgium) and at the Laboratoire Astroparticule et Cosmologie (APC) at Université Paris Cité (UPCité) are welcoming applications for a joint PhD student position in multi-messenger astronomy, to work on the joint detection of neutrinos and gravitational waves.
Tremendous advances in our knowledge of the origin of Galactic cosmic-rays (CR) have been made during the last decades. In particular, shock acceleration theory and observations with X-ray and gamma-ray have confirmed that the remnants of supernova explosions do accelerate particles. But so far, no evidence supports their ability to produce particles up to the knee energy of CRs around the PeV range. Gamma-rays in the very high energy (VHE, around the TeV) and ultra-high energy (UHE, beyond 100 TeV) domains are the key observables to search for extreme Galactic accelerators.
Pulsars are extremely magnetised spinning cosmic objets which emit beams of electromagnetic radiation from the radio band up to high-energy (HE; <100 GeV) and very-high-energy (VHE; >100 GeV) gamma-ray domain. While about 10% of the ~3000 radio pulsars are known to emit gamma-rays in the HE range, only three pulsars have up to now been detected in the VHE domain.
There is a general consensus that every galaxy harbors a supermassive black hole (SMBH) at its nucleus. While we cannot easily study these exotic objects directly, we can investigate how they interact with their surroundings. When an SMBH accretes matter, it becomes active and starts radiating, primarily emitting thermal photons from the accretion disk that feeds it. These accreting SMBHs, known as Active Galactic Nuclei (AGNs), are among the brightest sources of photons in the Universe.
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.
