http://arxiv.org/abs/2205.15040
The third observing run of the LIGO/Virgo/KARGA collaboration reported a few neutron star – black hole (NSBH) merger events. While NSBH mergers have yet to receive extensive theoretical attention, they may have a promising electromagnetic signature in the form of short gamma – ray bursts. Here we show that NSBH dynamical mergers can naturally form from ultra – wide binaries in the field. Flyby gravitational interactions with other neighbors in the galaxy in these ultra – wide systems may result in high eccentricity that drives the binary into a merger. We show that this process can result in a merger rate at the order of $\sim 10$~Gpc$^{-3}$~yr$^{-1}$ ($\sim 5$~Gpc$^{-3}$~yr$^{-1}$) for elliptical (spiral) galaxies. This channel predicts higher merger rate with higher velocity dispersion of the host – galaxy, delay time distribution which shallower than uniform but steeper that $1/t$, higher merger rate for lower BH to NS mass ratio.
E. Michaely and S. Naoz
Tue, 31 May 22
17/89
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