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Title: Using the Hills Mechanism to Generate Repeating Partial Tidal Disruption Events and ASASSN-14ko
Abstract Periodic nuclear transients have been detected with increasing frequency, with one such system—ASASSN-14ko—exhibiting highly regular outbursts on a timescale of 114 ± 1 days. It has been postulated that the outbursts from this source are generated by the repeated partial disruption of a star, but how the star was placed onto such a tightly bound orbit about the supermassive black hole remains unclear. Here we use analytic arguments and three-body integrations to demonstrate that the Hills mechanism, where a binary system is destroyed by the tides of the black hole, can lead to the capture of a star on a ∼114 days orbit and with a pericenter distance that is comparable to the tidal radius of one of the stars within the binary. Thus, Hills capture can produce stars on tightly bound orbits that undergo repeated partial disruption, leading to a viable mechanism for generating not only the outbursts detected from ASASSN-14ko but periodic nuclear transients in general. We also show that the rate of change of the period of the captured star due to gravitational-wave emission is likely too small to produce the observed value for ASASSN-14ko, indicating that in this system there must be additional effects that more » contribute to the decay of the orbit. In general, however, gravitational-wave emission can be important for limiting the lifetimes of these systems and could produce observable period decay rates in future events. « less
Authors:
; ;
Award ID(s):
2006684
Publication Date:
NSF-PAR ID:
10350422
Journal Name:
The Astrophysical Journal Letters
Volume:
929
Issue:
2
Page Range or eLocation-ID:
L20
ISSN:
2041-8205
Sponsoring Org:
National Science Foundation
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