Astro Seminar: Alessio L. De Santis

Speaker: Alessio L. De Santis (GSSI)

Title: What gamma-ray burst observations tell us about the population of binary neutron star mergers

Abstract:
The landmark multi-messenger observations of the binary neutron star (BNS) merger event GW170817 provided firm evidence that BNS mergers can serve as progenitors of short gamma-ray bursts (sGRBs). However, the limited number of BNS detections by gravitational-wave observatories to date raises questions about whether BNS mergers alone can account for the full population of observed sGRBs. Starting from a comprehensive set of BNS population synthesis models, we develop a theoretical framework based on Monte Carlo simulations to reproduce the observable properties of sGRBs. Using the sample of sGRBs detected by Fermi-GBM over the past 16 years, we calibrate both the BNS merger population and the properties of the jets produced by these mergers to match the observed Fermi data. The anti-correlation between the intrinsic BNS merger rates predicted by the models and the fraction of mergers that successfully launch relativistic jets enables us to identify and rank the BNS population models that are the most plausible progenitor candidates for sGRBs. We show that combining gravitational-wave constraints on the BNS merger rate with electromagnetic constraints from sGRBs is a powerful approach to constrain both BNS population models and sGRB jet properties.