Recently, the observational study of gamma-ray bursts (GRBs) in the very-high-energy (VHE) regime has advanced with several long-awaited detections with MAGIC and H.E.S.S. telescope systems. Currently, the list of GRBs with robustly measured VHE emissions contains GRB 180720B, GRB 190114C, and GRB 190829A. Three more bursts were reported as source candidates by the MAGIC Collaboration. This...
GRBs’ progenitors are also sources of gravitational waves. Binary neutron star mergers that are progenitors of short GRBs are the classical sources of chirping GW signals. Long GRBs arise from Collapsars. While GWs haven’t been observed yet from collapsing stars, a non-spherical collapse would be a source of a burst of GWs. In addition, both long and short GRBs involve the acceleration of...
The intense star-forming activity typical of starburst galaxies results in unique conditions for high-energy particles. The enhanced supernova rate associated with such star formation can in fact transfer a large amount of power to non-thermal particles which, in turn, can lose most of their energy in the dense and perturbed starburst environment before being able to escape it.
I will...
Massive stars blow powerful winds and eventually explode as supernovae. By doing so, they inject energy and momentum in the circumstellar medium, which is pushed away from the star and piles up to form a dense and expanding shell of gas. The effect is larger when many massive stars are grouped together in bound clusters or associations. Large cavities form around clusters as a result of the...
Binary systems are today well established gamma-ray emitters, and the variety of the processes responsible for this emission is a hard act to follow among any other high-energy source class. After years of faithful perspectives, extensive theoretical modelling and complex MHD simulations, GeV/TeV detectors have reported a too rich phenomenology to be predicted just a few years ago. I will...
Classical and recurrent nova explosions occur on top of white dwarfs accreting H-rich matter from a companion main sequence or red giant star, in a close binary system. In the recent years, since the launch of the Fermi Gamma-Ray satellite by NASA in 2008, several novae have been detected by Fermi/LAT (LAT: Large Area Telescope) in High-Energy Gamma Rays, with energies larger than 100 MeV....
On 2017 August 17, the merger of a binary neutron-star system observed through gravitational waves and multi-wavelength emission from gamma rays, X-ray, ultraviolet-optical-near infrared, to radio marked the history of multi-messenger astronomy, showing its tremendous potential probe the physics of the most energetic events of the Universe. Multi-messenger discoveries are unveiling the rich...
Current knowledge of the Universe is based on information carried by electromagnetic radiation, gravitational waves, neutrinos, and cosmic rays. For over a century, scientists have observed cosmic rays, but the understanding of their place of production is limited. As a product of cosmic ray interaction, neutrinos can shed light on the extreme part of the Universe. IceCube Neutrino Observatory...
Pulsar wind nebulae (PWNe) are multi-wavelength bright sources produced by the interaction of the relativistic, magnetized and cold plasma emanating from the neutron star with the surrounding material, either the ejecta of the supernova explosion or the interstellar medium, depending on their phase of evolution.
They will constitute the widest class of Galactic gamma-ray sources of future...
Supernova remnants (SNRs) are now established as cosmic particle accelerators through observations of non-thermal emissions from radio to gamma-ray domain in the past decades. In the context of Galactic cosmic-ray origin, one of the key questions was if they are proton accelerators. At least for some SNRs, gamma-ray emissions are solidly attributed to decay of neutral pions, providing...
In the most powerful astrophysical sources, reconnection and turbulence operate in the “relativistic” regime, where the magnetic field energy exceeds even the rest mass energy of the plasma. Here, reconnection and turbulence can lead to fast dissipation rates and efficient particle acceleration, thus being prime candidates for powering the observed fast and bright flares of high-energy...
