Astrophysique à Haute Energie

Magnetar birth as engine of extreme stellar explosions

The birth of a neutron star with an extremely strong magnetic field, called a magnetar, has emerged as a promising scenario to power a variety of outstanding explosive events. This includes gamma-ray bursts, supernovae with extreme kinetic energies called hypernovae and super-luminous supernovae. The origin of these extreme magnetic fields (of the order of 10^15 Gauss) remains, however, obscure and requires an amplification over several orders of magnitude during the formation of the neutron star.

The many faces of pulsars 

Pulsars are rapidly rotating, strongly magnetised neutron stars, 
emitting flashes of non-thermal radiation covering up to eighteen decades of 
energy in the electromagnetic spectrum.
They are powerful tools used in physics, astronomy and even cosmology.
I’ll review their observational status and prospects for the future.
I’ll then present current models of high-energy processes as well as new
theoretical developments in modeling pulsars and their wind zones.

The supernova remnant pevatron population in the TeV sky

The supernova remnant hypothesis for the origin of Galactic cosmic rays has
passed several tests, but the firm identification of a supernova remnant
pevatron, considered to be a decisive step to prove the hypothesis, is still
missing.
While a lot of hope has been placed in next-generation instruments
operating in the multi-TeV range, it is possible that current gamma-ray
instruments, operating in the TeV range, could pinpoint these objects or, most
likely, identify a number of promising targets for instruments of next

The Extreme Physics of Neutron Stars — An observer’s view point

Neutron stars are fantastic cosmic laboratories to study the most extreme physics. Their intense gravitational fields can provide tests of general relativity and other theories of gravitation. Their unmatched magnetic fields permit studies of the interaction between matter and these fields. And their extreme interior densities allow us to probe matter in regimes not accessible to Earth laboratories.  
 

O2 multi-messenger campaign and future prospects with the SVOM mission

The O2 follow-up campaign of gravitational wave candidate (GW) events was intensive with the collaboration of 95 groups in astronomy and astro-particle physics.  Since the size of the localization error of GW is quite large, the follow-up strategy for finding counterpart of GW alerts is quite complex. However, the joint accomplishment was rewarded with the first multi-messenger probe of the merger of a binary neutron stars (GW170817), an associated electromagnetic counterpart as gamma-ray burst (GRB170817A) and bright multiwavelength isotropic emission.

On-ground multipoint radiation measurement discovering atmospheric photonuclear reactions triggered by lightning discharge in Japan

Energetic radiation associated with thunderstorm activities have been detected by on-ground, airborne, rocket-triggered lightning experiments, as well as in-orbit detectors as terrestrial gamma-ray flashes (TGFs). The high energy emissions, including bremsstrahlung gamma rays with energy extending up to 20 MeV, indicate powerful electron accelerations inside thunderclouds or along lightning discharge paths. We focus on unique characteristics of winter thunderstorms such as lower cloud bases and powerful activities, and started a multipoint mapping observation campaign since 2015.

Solar neutrinos: from MeV to TeV

The observation of solar neutrinos in the late sixties represents an important milestone in (astro-) particle physics. According to theoretical predictions, the Sun may turn out to be an exceptional neutrino factory producing, in addition to the already observed MeV neutrinos from fusion, neutrinos up to TeV energies. I will review the different processes that might lead to a significant signal in neutrino observatories in  the near future.

X-ray spectral index correlations vs mass accretion rate in neutron star and black hole X-ray binaries in their different spectral states. Theory vs observations

I present  details  of observations of neutron star (NS) and black hole (BH) binaries and the first principle theory of X-ray spectral formation in neutron star (NS) and black hole (BH) there.  I show that this model predicts the spectral index correlation vs mass accretion rate  as in the case of NS as well in the BH case.  In BHs the spectral index should increase and then saturate with mass accretion rate, because the index is an inverse  of Comptonization parameter Y and  Y-parameter saturates with the high mass accretion rate in the converging flow onto BH.

Simulating the interaction between non-thermal particles and the magnetic field in astrophysical shocks

Cosmic rays are charged particles that have been accelerated to high velocities as they cross astrophysical shocks. This acceleration process involves repeated interactions between the particles and the local magnetic field, which not only influence the velocity of the particles, but the morphology of the magnetic field, and therefore the shock structure, as well. 

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