Abstract
ABSTRACT Mergers of binaries comprising compact objects can give rise to explosive transient events, heralding the birth of exotic objects that cannot be formed through single-star evolution. Using a large number of direct N-body simulations, 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 an 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, adiabatic mass loss, semimajor axes and eccentricities of the triples, and stellar-mass ratios. We find rates of WD–tidal disruption events (TDEs) in the range 1.2 × 10−3 − 1.4 Gpc−3 yr−1 for z ≤ 0.1, rarer than stellar TDEs in triples by a factor of ∼3–30. The uncertainty in the TDE rates may be greatly reduced in the future using 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 that 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.
Highlights
Mergers of binaries comprising two compact objects have been the subject of numerous theoretical investigations over the past several years
Compared to the fraction of stable systems assuming kicks only, we find that the fraction of stable triples that can lead to a black hole (BH)–white dwarf (WD) merger is increased by a factor of ∼3–20 in the case that the mass loss is adiabatic only
This paper explores a new triple channel for WD–BH mergers driven by the joint effect of gravitational wave (GW) emission and the LK mechanism
Summary
Mergers of binaries comprising two compact objects have been the subject of numerous theoretical investigations over the past several years. To date, ∼20 NS–WD binaries have been confirmed in our Galaxy (van Kerkwijk et al 2005), while only one field BH–WD binary candidate is presently known (Bahramian et al 2017) In such binaries, the WD may approach the NS or BH close enough to be disrupted as a tidal disruption event (WD–TDE). Several works have characterized the possible electromagnetic (EM) signatures of the tidal disruption of a WD by an NS or a BH (Fryer et al 1999; King, Olsson & Davies 2007; Metzger 2012; Fernandez & Metzger 2013; Margalit & Metzger 2016; Bobrick, Davies & Church 2017; Toonen et al 2018a; Fernandez, Margalit & Metzger 2019; Zenati, Perets & Toonen 2019) Such events may produce a high-energy transient similar to a GRB, or thermal emission similar to a shortlived supernova (Metzger 2012; Zenati et al 2019).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
