Joint study of Fermi/LAT and Swift/XRT detected gamma-ray bursts with extended afterglow emission

Abstract

The main aim of the project is to do a joint study of Fermi/LAT and Swift/XRT detected Gamma-Ray Bursts (GRBs) with extended afterglow emission. GRBs are the most energetic electromagnetic transients in Universe, spewing out intense bursts of photons from keV to TeV energies with a duration of a few milliseconds up to days. Depending on the duration, GRBs are classified into two types: short GRBs (SGRBs) and long GRBs (LGRBs) with a duration of less than 2s and more than 2s, respectively. In the case of LGRBs, the collapse of a massive star produces an ultra-relativistic jet which gives rise to a highly variable and luminous gamma-ray emission. This prompt emission is then followed by a multi-wavelength afterglow emission due to the external dissipation of the jet in the circumburst medium. In most cases, the Fermi/LAT GRBs (0.1-100GeV) emission follows a regular decay pattern as expected from the standard afterglow model. However, some of the LAT-GRBs show slower decay. In this work, we select such GRBs from the latest Fermi/LAT catalog and quantify the disagreement between the observed emission and the prediction of the afterglow emission. In addition to that, we also studied the X-ray light curves in order to evaluate these cases in multi-wavelength scenarios.