Kilonova and progenitor properties of merger-driven gamma-ray bursts

Gamma-ray burst (GRB) prompt and afterglow emission, as well as kilonova (KN) emission, are the expected electromagnetic (EM) counterparts of binary neutron star (BNS) and neutron star-black hole (NSBH) mergers. Only one BNS merger (GW170817) detected on the basis of gravitational waves (GWs) has a confirmed association with EM counterparts. Without a GW signal, the ejecta parameters from a KN can be used to infer the progenitor properties. We aim to infer the KN ejecta parameters and the progenitor properties by modeling merger-driven GRBs with a claim of KN, good data, and robust redshift measurements. We modeled the afterglow and KN, performing a Bayesian analysis, within the Nuclear physics and Multi-Messenger Astrophysics () framework. The KN emission is modeled with the radiative transfer code and for the afterglow, we used the library. In contrast to previous approaches, our methodology simultaneously models both the afterglow and KN. NMMA POSSIS afterglowpy We find that all GRBs in our sample have a KN, but we were unable to confirm or exclude its presence in GRB, 150101B. A BNS progenitor is favored for GRB, 160821B, GRB, 170817A/AT2017gfo, GRB, 211211A, and GRB, 230307A. For GRB, 150101B and GRB, 191019A, we found a slight preference for the NSBH scenario; however, a BNS is also a viable possibility. For the KN emission, we see that the median wind mass łangle ̊m wind ̊angle=0. 027^ +0. 046 _ -0. 019 M_⊙ is higher than the dynamical łangle M_ ̊m dyn ̊angle = 0. 012^ +0. 007 _ -0. 006 M_⊙. Finally, we find that M_̊m wind and the collimation-corrected energy of the jet can be expressed as log (M_ ̊m wind) =-20. 23+0. 38, log (E_ 0, J). We confirm the results of numerical simulations, demonstrating that the mass-weighted tidal deformability, tildeΛ, increases along with a decrease in the chirp mass, mathcal M _ ̊m, Chirp. Our results exemplify and reinforce that EM modeling is the only feasible pathway to investigate binary mergers in absence of GW observations. In this work, we present for the first time the binary progenitor properties of a sizable sample of merger-driven GRBs.