Ponente
Descripción
A considerable fraction of the energy from gamma-ray burst (GRB) jets, after generating the keV-MeV emissions, results in an ultra-relativistic shock that travels through the circumburst medium. This shock accelerates particles, resulting in afterglow emissions. Recently, a few GRB afterglows have been detected in TeV gamma-rays by Cherenkov Telescopes, offering a chance to examine the broadband spectra. These spectra provide valuable insights into the microphysics of relativistic shocks and the structure of the surrounding medium. The transition from synchrotron to inverse Compton (IC) in the afterglow spectra occurs between hard X-rays and very-high-energy (VHE) gamma-rays; hence, detecting emissions in at least one of these bands is crucial to identify the origin of the spectral components. Early afterglow data in the hard X-rays and GeV energies can precisely define the spectral shape and aid in identifying the spectral turnover and differentiating the two components. We performed a multiwavelength analysis of the spectral and temporal characteristics, concentrating on the keV-GeV range of GRB~230812B, one of the brightest GRBs recorded by the Fermi Gamma Ray Burst Monitor (Fermi/GBM). Additionally, a 72 GeV photon was observed with the Large Area Telescope (Fermi/LAT) during the early afterglow phase. By thoroughly modeling the emission from the afterglow external forward shock in a wind-like environment, we predict optical to high-energy observations that extend to roughly one day. We stress the significance of pursuing observation of poorly localized GRBs by illustrating that even without immediate localization, as with GRB 230812B, the GRB can be detected using imaging atmospheric Cherenkov telescopes (IACTs), benefitting from their large field of view. Moreover, I will demonstrate the importance of a low energy threshold of the Large-Sized Telescope for discovering the VHE emission from GRBs at much higher redshifts.
