The observational potentials of the advanced detector system of the HERMES Pathfinder mission, an assessment

HERMES (High Energy Rapid Modular Ensemble of Satellites) Pathfinder is a space-borne mission based on a constellation of 3U CubeSats, flying in a low-Earth orbit, equipped with a novel specifically designed detector obtained by the combination of silicon drift detectors and GAGG:Ce crystal scintillators, exploiting the "siswich" architecture. HERMES Pathfinder main scientific goal is the study of bright high‐energy transients, the gamma‐ray bursts, in a broad energy band (few keV to few MeV) with an unprecedented time resolution and a precise localization. The crystal scintillator chosen for the HERMES Pathfinder detector presents an intense and long lasting residual emission (afterglow) after being exposed to ionizing radiation. This phenomenon might affect the HERMES Pathfinder detectors, impairing their proper functioning. In this study the crystal afterglow has been characterized and it was verified that, in orbital conditions, the correct functioning of the detector is guaranteed. In preparation for the nanosatellites launch, the qualification performed during the assembling of the detector and the final calibration of the HERMES Pathfinder payload at several temperature have been performed. The methods and the results obtained for the first flight models are presented in this study. Finally, a tool was developed to study the lightcurve variability of a GRB and to identify its shortest variability in order to provide new insights on the central engine. It was tested on a large set of bursts observed by Fermi GBM. Finally, using a simulated data, it is demonstrated that variability of the order of microseconds could be identified with this tool.