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Title: Gravitational interactions of stars with supermassive black hole binaries – I. Tidal disruption events

Abstract

Stars approaching supermassive black holes (SMBHs) in the centres of galaxies can be torn apart by strong tidal forces.We study the physics of tidal disruption by a circular, binary SMBH as a function of the binary mass ratio q = M 2/M 1 and separation a, exploring a large set of points in the parameter range q ϵ [0.01, 1] and a/r t1 ϵ [10, 1000]. We simulate encounters in which field stars approach the binary from the loss cone on parabolic, low angular momentum orbits. We present the rate of disruption and the orbital properties of the disrupted stars, and examine the fallback dynamics of the post-disruption debris in the ‘frozen-in’ approximation. We conclude by calculating the time-dependent disruption rate over the lifetime of the binary. Throughout, we use a primary mass M 1 = 10 6 M as our central example. We find that the tidal disruption rate is a factor of ~2–7 times larger than the rate for an isolated BH, and is independent of q for q ≳ 0.2. In the ‘frozen-in’ model, disruptions from close, nearly equal mass binaries can produce intense tidal fallbacks: for binaries with q ≳ 0.2 and a/r t1 ~ 100, roughly ~18–40 per cent of disruptions will have short rise times (t rise ~ 1–10 d) and highly super-Eddington peak return rates ( $$\dot{M}$$ peak/ $$\dot{M}$$ Edd ~ 2 × 102–3 × 103).

Authors:
 [1];  [1];  [2];  [1]
  1. Univ. of California, Berkeley, CA (United States)
  2. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC); Univ. of California, Oakland, CA (United States)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1543985
Grant/Contract Number:  
[AC02-05CH11231]
Resource Type:
Accepted Manuscript
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
[ Journal Volume: 477; Journal Issue: 3]; Journal ID: ISSN 0035-8711
Publisher:
Royal Astronomical Society
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; Astronomy & Astrophysics

Citation Formats

Darbha, Siva, Coughlin, Eric R., Kasen, Daniel, and Quataert, Eliot. Gravitational interactions of stars with supermassive black hole binaries – I. Tidal disruption events. United States: N. p., 2018. Web. doi:10.1093/mnras/sty822.
Darbha, Siva, Coughlin, Eric R., Kasen, Daniel, & Quataert, Eliot. Gravitational interactions of stars with supermassive black hole binaries – I. Tidal disruption events. United States. doi:10.1093/mnras/sty822.
Darbha, Siva, Coughlin, Eric R., Kasen, Daniel, and Quataert, Eliot. Mon . "Gravitational interactions of stars with supermassive black hole binaries – I. Tidal disruption events". United States. doi:10.1093/mnras/sty822. https://www.osti.gov/servlets/purl/1543985.
@article{osti_1543985,
title = {Gravitational interactions of stars with supermassive black hole binaries – I. Tidal disruption events},
author = {Darbha, Siva and Coughlin, Eric R. and Kasen, Daniel and Quataert, Eliot},
abstractNote = {Stars approaching supermassive black holes (SMBHs) in the centres of galaxies can be torn apart by strong tidal forces.We study the physics of tidal disruption by a circular, binary SMBH as a function of the binary mass ratio q = M2/M1 and separation a, exploring a large set of points in the parameter range q ϵ [0.01, 1] and a/rt1 ϵ [10, 1000]. We simulate encounters in which field stars approach the binary from the loss cone on parabolic, low angular momentum orbits. We present the rate of disruption and the orbital properties of the disrupted stars, and examine the fallback dynamics of the post-disruption debris in the ‘frozen-in’ approximation. We conclude by calculating the time-dependent disruption rate over the lifetime of the binary. Throughout, we use a primary mass M1 = 106 M⊙ as our central example. We find that the tidal disruption rate is a factor of ~2–7 times larger than the rate for an isolated BH, and is independent of q for q ≳ 0.2. In the ‘frozen-in’ model, disruptions from close, nearly equal mass binaries can produce intense tidal fallbacks: for binaries with q ≳ 0.2 and a/rt1 ~ 100, roughly ~18–40 per cent of disruptions will have short rise times (trise ~ 1–10 d) and highly super-Eddington peak return rates ( $\dot{M}$peak/ $\dot{M}$Edd ~ 2 × 102–3 × 103).},
doi = {10.1093/mnras/sty822},
journal = {Monthly Notices of the Royal Astronomical Society},
number = [3],
volume = [477],
place = {United States},
year = {2018},
month = {4}
}

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