The discovery of GW170817 with gravitational waves (GWs) and electromagnetic (EM) radiation is prompting new questions in strong-gravity astrophysics. Importantly, it remains unknown whether the progenitor of the merger comprised two neutron stars (NSs), or a NS and a black hole (BH). Using new numerical-relativity simulations and incorporating modeling uncertainties we produce novel GW and EM observables for NS-BH mergers with similar masses. A joint analysis of GW and EM measurements reveals that if GW170817 is a NS-BH merger, <40% of the binary parameters consistent with the GW data are compatible with EM observations.
@article{arxiv.1808.03836,
title = {Distinguishing the nature of comparable-mass neutron star binary systems with multimessenger observations: GW170817 case study},
author = {Tanja Hinderer and Samaya Nissanke and Francois Foucart and Kenta Hotokezaka and Trevor Vincent and Mansi Kasliwal and Patricia Schmidt and Andrew R. Williamson and David Nichols and Matthew Duez and Lawrence E. Kidder and Harald P. Pfeiffer and Mark A. Scheel},
journal= {arXiv preprint arXiv:1808.03836},
year = {2020}
}