Speaker
Description
Gamma-ray bursts are some of the most bright (energetic) X-ray and Gamma-ray flashes, very exotic events observed in the entire Universe, emitted by distant extragalactic sources. They are associated with collapsing SMBHs or the creation or merging of neutron stars. These processes are the results of an explosive outburst of materials that move incredibly near the speed of light. The initial bursts, which usually last a few seconds are followed by a long-lasting afterglow phase that can be detected for several days in the X-ray bands, and often weeks/months in optical/radio bands. It is in the afterglow emission that GRBs were first confirmed as of extragalactic origin. The afterglow emission in the X-ray band is produced by accelerated electrons that lose energy as they interact within a blast wave of the magnetic field. Such energetic photons are well described by Synchrotron models. GRB afterglows are essentially an excellent cosmic laboratory when studying the acceleration of particles in the Universe due to the simplicity of underlying physics. On the other hand, it's much more complex up to now to reveal the exact properties of the prompt phase of GRBs. Many properties of afterglow emission in X-ray/optical band are well known, however, it remains an open question to understand the correlation of X-ray and VHE emissions ($>$ 100 GeV), that's $10^6$ energetic than X-ray emission. Since 2004, H.E.S.S have been observing GRBs and since then more than 120 GRBs were observed. However, only 2 GRBs (GRB 180720B, GRB 190829A) have been detected above 5 sigma of significance, while others are upper limits. The main objective of this study is to search for the correlation between X-ray/optical and VHE emissions. I will perform modeling of mainly X-ray data and gamma-ray fluxes to predict the multi-wavelength lightcurves and SEDs of a sample of GRBs from H.E.S.S. The main focus will be on GRBs detected by Swift data and that have the redshift.
