Orateur
Description
Gamma-ray bursts (GRBs) are powerful, brief flashes of gamma-rays produced either by the merger of two compact objects (Type-I) or by the core-collapse of some kind of massive star (Type-II). While short-duration GRBs have traditionally been associated with mergers and long GRBs with collapsars, an increasing number of long-duration events, such as GRB 230307A associated with kilonovae emission, show robust evidence for a compact object merger origin. These discoveries challenge traditional classification schemes and demand new methods to reliably identify GRB progenitors from their prompt emission. In this talk, I will review existing techniques aimed at identifying GRB progenitors from their prompt emission and present a recent work in which we identified a set of distinctive temporal features in the light curve of GRB 230307A. A similar behaviour is observed in other long merger candidates, such as GRB 211211A, whereas it is not observed in any long GRBs associated with a Ic-BL SN. Extending this study to the whole Fermi/GBM catalogue, we identified 9 additional GRBs with unknown redshift, showing a similar behaviour. Using their tracks in the E_{p,i}-E_{iso} plane, we showed that at least two of these GRBs are outliers of the Amati relation for Type-II GRBs, aligning instead with Type-I GRBs, a conclusion that is also supported by their short minimum variability timescales. Finally, I will outline the usefullness of these signatures to promptly identify long Type-I GRBs directly from their light curves and the implications for their multi-wavelength follow-up campaigns.