One of the most important and still largely unknown events in the universe are Gamma-ray Bursts (GRB). GRB are the most luminous events in Universe and probably the signature of the birth of black holes.

Nowadays, we know that there are two types of GRBs, based on the duration (long or short), to which we have associated two different model of formation ; we have distinguished two phases, prompt and afterglow, in the emission of the GRB ; and much more that has been already discovered. However, there are still many aspects to be explored or theories to be confirmed. For example there have been several models developped for the prompt mechanism, but it still need to be studied to understand which models are the ones that describe correctly the phenomena. In particular, since we are now entering the multimessenger era, GRBs are getting more and more attention, since recent discoveries showed a connection between short GRBs and gravitational waves.

The HERMES project will have as main goal to study GRBs. This mission will use a constellation of nanosatellites in Low Earth Orbit (LEO) to explore the universe in search of these luminous events. At first they will launch a six nanosatellites, but the objective is to reach a hundred of nanosatellites.

For my PhD, I will focus on the study of one of the aspects of GRBs that are still unclear and need to be deepened, the microvariability of GRBs. The microvaribility represents the lowest timescale on which the GRB lightcurve shows an important variation. This value is important since it allows to put constraints others aspects of the GRBs. In order to study the microvariability, I will develop a method to determine this value, based on studies presented in the litterature, and apply it on future data that HERMES will provide.

Also, to have a better understanding of the HERMES nanosatellites, I’ll be working directly on the advanced detectors used on board, i.e. the GAGG scintillation crystals of recent development and the Silicon Drift Detectors (SDDs) developed on purpose for this experiment. The coupling of these two detection elements will offer new observational capabilities in two different energy windows with a high energy and timing resolution. I will focus in particular on the characterization of the coupling of GAGG and SDD.