Simulations of neutron star-black hole ( NSBH ) binaries generally consider black holes with masses in the range ( 5 - 10 ) M _ { \odot } , where we expect to find most stellar mass black holes .
The existence of lower mass black holes , however , can not be theoretically ruled out .
Low-mass black holes in binary systems with a neutron star companion could mimic neutron star-neutron ( NSNS ) binaries , as they power similar gravitational wave ( GW ) and electromagnetic ( EM ) signals .
To understand the differences and similarities between NSNS mergers and low-mass NSBH mergers , numerical simulations are required .
Here , we perform a set of simulations of low-mass NSBH mergers , including systems compatible with GW170817 .
Our simulations use a composition and temperature dependent equation of state ( DD2 ) and approximate neutrino transport , but no magnetic fields .
We find that low-mass NSBH mergers produce remnant disks significantly less massive than previously expected , and consistent with the post-merger outflow mass inferred from GW170817 for moderately asymmetric mass ratio .
The dynamical ejecta produced by systems compatible with GW170817 is negligible except if the mass ratio and black hole spin are at the edge of the allowed parameter space .
That dynamical ejecta is cold , neutron-rich , and surprisingly slow for ejecta produced during the tidal disruption of a neutron star : v \sim ( 0.1 - 0.15 ) c .
We also find that the final mass of the remnant black hole is consistent with existing analytical predictions , while the final spin of that black hole is noticeably larger than expected – up to \chi _ { BH } = 0.84 for our equal mass case .