On the Origins, Remnant, and Multimessenger Prospects of the Compact Binary Merger GW230529

Abstract This study investigates the origins of GW230529, delving into its formation from massive stars within isolated binary systems. Utilizing population-synthesis models, we present compelling evidence that the neutron star component forms second. However, the event’s low signal-to-noise ratio introduces complexities in identifying the underlying physical mechanisms driving its formation. Augmenting our analysis with insights from numerical relativity, we estimate the final black hole mass and spin to be approximately 5.3 M ⊙ and 0.53, respectively. Furthermore, we employ the obtained posterior samples to calculate the ejecta mass and kilonova light curves resulting from r -process nucleosynthesis. We find the ejecta mass to be within 0–0.06 M ⊙ , contingent on the neutron star equation of state. The peak brightness of the kilonova light curves indicates that targeted follow-up observations with a Rubin-like observatory may have detected this emission.