Gamma-ray bursts at Very High Energy: Clues from their host environments
Résumé
Abstract
Gamma-ray bursts (GRBs) are beginning to be regularly detected by ground-based Cherenkov telescopes at the TeV range. Although the number of detections is still small, it is expected to grow dramatically as the new telescopes of the CTA observatories come online. It has been discussed that the local environment in which the explosion is produced may play a role in the production of these VHE photons and we are using host galaxy observations to derive conclusions on this.
We present a systematic study of the host environment of GRBs detected at VHE with Cherenkov telescopes. We observed the host galaxies using optical and IR photometry to derive their properties through spectral energy distribution fits. The results are complemented with broad-band observations of the afterglow, which are used to understand the overall emission mechanisms, to understand if further components, such as inverse Compton are required to explain the VHE photons or if a simple synchrotron spectrum is enough. Furthermore, we compare with spectoscopic observations of the afterglows that tell us about the line of sight properties of the interstellar medium within the host galaxies.
Comparing with the general sample of GRB host galaxy environments, we can identify peculiarities, such as large circumburst densities, unique absorption features, or local dust content.