http://arxiv.org/abs/1908.00987
Mergers of binaries comprised of two compact objects have been under recent intense scrutiny. Such mergers can give rise to explosive transient events, heralding the birth of exotic objects which cannot be formed through single star evolution. Using a large number of direct N-body simulations, in this paper we explore the possibility that a white dwarf (WD) is dynamically driven to tidal disruption by a stellar-mass black hole (BH) as a consequence of the joint effects of gravitational wave (GW) emission and Lidov-Kozai oscillations imposed by the tidal field of a outer tertiary companion orbiting the inner BH-WD binary. We explore the sensitivity of our results to the distributions of natal kick velocities imparted to the BH and WD upon formation, semi-major axes and eccentricities of the triples, and stellar mass ratios. Under the assumption of momentum-conserving natal kicks, we find rates of WD-TDEs through the triple channel in the range $1.2\times 10^{-3}-1.4$ Gpc$^{-3}$ yr$^{-1}$ for $z\leq 0.1$, rarer than stellar TDEs in triples by a factor of $\sim 3$–$30$, depending on the magnitude of the natal kicks. The uncertainty in the TDE rates may be greatly reduced in the future using gravitational wave (GW) observations of Galactic binaries and triples with LISA. WD-TDEs may give rise to high energy X-ray or gamma-ray transients of duration similar to long gamma-ray bursts but lacking the signatures of a core-collapse supernova, while being accompanied by a supernova-like optical transient which lasts for only days. WD–BH and WD–NS binaries will also emit GWs in the LISA band before the TDE. The discovery and identification of triple-induced WD-TDE events by future time domain surveys and/or GWs could enable the study of the demographics of BHs in nearby galaxies.
G. Fragione, B. Metzger, R. Perna, et. al.
Tue, 6 Aug 19
2/76
Comments: 11 pages, 7 figures, 1 table
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