2020ApJ...890L...4K -
Astrophys. J., 890, L4-L4 (2020/February-2)
On the possibility of GW190425 being a black hole-neutron star binary merger.
KYUTOKU K., FUJIBAYASHI S., HAYASHI K., KAWAGUCHI K., KIUCHI K., SHIBATA M. and TANAKA M.
Abstract (from CDS):
We argue that the kilonova/macronova associated with the gravitational-wave event GW190425 could have been bright enough to be detected if it was caused by the merger of a low-mass black hole (BH) and a neutron star (NS). Although tidal disruption occurs for such a low-mass BH is generally expected, the masses of the dynamical ejecta are limited to <=10–3 M☉, which is consistent with previous work in the literature. The remnant disk could be as massive as 0.05-0.1 M☉, and the disk outflow of ∼0.01-0.03 M☉ is likely to be driven by viscous or magnetohydrodynamic effects. The disk outflow may not be neutron-rich enough to synthesize an abundance of lanthanide elements, even in the absence of strong neutrino emitter, if the ejection is driven on the viscous timescale of >=0.3 s. If this is the case, the opacity of the disk outflow is kept moderate, and a kilonova/macronova at the distance of GW190425 reaches a detectable brightness of 20-21 mag at 1 day after merger for most viewing angles. If some disk activity ejects the mass within ∼0.1 s, instead, lanthanide-rich outflows would be launched and the detection of emission becomes challenging. Future possible detections of kilonovae/macronovae from GW190425-like systems will disfavor the prompt collapse of binary NSs and a non-disruptive low-mass BH-NS binary associated with a small NS radius, whose mass ejection is negligible. The host-galaxy distance will constrain the viewing angle and deliver further information about the mass ejection.
Abstract Copyright:
© 2020. The American Astronomical Society. All rights reserved.
Journal keyword(s):
Neutron stars - Black holes - Gravitational wave sources - Compact binary stars - Time domain astronomy
Simbad objects:
2
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