2026/02/13 by A. L. De Santis, Alessio Ludovico De Santis, S. Ronchini +5
Physics and Astronomy · #Gamma-ray bursts and supernovae #Pulsars and Gravitational Waves Research #Space Science and Extraterrestrial Life
paper · pdf · doi:10.1051/0004-6361/202659597
The landmark multi-messenger observations of the binary neutron star (BNS) merger GW170817 provided firm evidence that such mergers can produce short gamma-ray bursts (sGRBs). However, the limited number of BNS detections by current gravitational wave observatories raises the question of whether BNS mergers alone can account for the full observed sGRB population. We analysed a comprehensive set of 64 BNS population synthesis models with a Monte Carlo–based framework to reproduce the properties of sGRBs detected by Fermi -GBM over the past 16 years. We considered three jet geometry scenarios: a universal structured jet calibrated to GW170817, a universal top-hat jet, and a non-universal top-hat jet with distributions of core opening angles. Our results show that models characterised by low local BNS merger rates ( R BNS (0) ≲ 50 Gpc −3 yr −1 ) predict too few observable sGRBs to reproduce the Fermi -GBM population, effectively disfavouring them as sole progenitors. Even when relaxing the assumptions on jet geometry, low-rate models remain viable only for wide jets ( θ c ≥ 15°), in tension with the narrow jet cores ( θ c ≈ 6°) inferred from sGRB afterglow observations. In contrast, models with local merger rates of order R BNS (0) ≈ 100 Gpc −3 yr −1 successfully reproduce the observed sGRB population, assuming a plausible fraction of BNS mergers launch relativistic jets and realistic jet geometries. This analysis highlights the power of combining binary neutron star population synthesis models with sGRB observations and comparing them with current gravitational wave constraints to assess the role of BNS mergers as sGRB progenitors and to identify any emerging tensions between these populations.