Disrupting Black Hole-Neutron Star Mergers with Monte Carlo Neutrino Transport Methods: Ejecta Behavior and the Absence of Detectable Kilonova Signal

Black hole-neutron star (BHNS) mergers offer unique insights into both gravitational wave astrophysics and multi-messenger astronomy. In this talk, I present results from simulations of BHNS mergers, utilizing Monte Carlo neutrino transport methods to model the dynamics of the post-merger ejecta. These simulations provide a detailed look at the behavior of the unbound material, its composition, and thermodynamic properties. Despite expectations, our findings reveal a surprising lack of a detectable kilonova signal, which could be indicative of specific ejecta characteristics or emission mechanisms. We also investigate the composition of the ejecta, exploring implications for nucleosynthesis, particularly r-process elements, and actinide production. These results may challenge existing models of electromagnetic counterparts in such merger events and offer new directions for future theoretical and observational efforts.