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Tidal Disruption of White Dwarfs from Ultra-close Encounters with Intermediate-mass Spinning Black Holes

Hass, Roland and Shcherbakov, Roman V. and Bode, Tanja and Laguna, Pablo (2012) Tidal Disruption of White Dwarfs from Ultra-close Encounters with Intermediate-mass Spinning Black Holes. Astrophysical Journal, 749 (2). Art. No. 117. ISSN 0004-637X.

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We present numerical relativity results of tidal disruptions of white dwarfs from ultra-close encounters with a spinning, intermediate-mass black hole (IMBH). These encounters require a full general relativistic treatment of gravity. We show that the disruption process and prompt accretion of the debris strongly depend on the magnitude and orientation of the black hole (BH) spin. However, the late-time accretion onto the BH follows the same decay, Ṁ ∝ t^(-5/3), estimated from Newtonian gravity disruption studies. We compute the spectrum of the disk formed from the fallback material using a slim disk model. The disk spectrum peaks in the soft X-rays and sustains Eddington luminosity for 1-3 yr after the disruption. For arbitrary BH spin orientations, the disrupted material is scattered away from the orbital plane by relativistic frame dragging, which often leads to obscuration of the inner fallback disk by the outflowing debris. The disruption events also yield bursts of gravitational radiation with characteristic frequencies of ~3.2 Hz and strain amplitudes of ~10^(–18) for galactic IMBHs. The optimistic rate of considered ultra-close disruptions is consistent with no sources found in the ROSAT all-sky survey. Future missions like Wide-Field X-ray Telescope could observe dozens of events.

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Additional Information:© 2012 The American Astronomical Society. Received 2011 October 12; accepted 2012 February 6; published 2012 March 29. The authors are thankful to Ramesh Narayan for fruitful discussions. R.V.S. is supported by NASA Hubble Fellowship grant HST-HF-51298.01. R.H. gratefully acknowledges support by the Natural Sciences and Engineering Council of Canada. This work is supported by NSF grants 0653443, 0855892, 0914553, 0941417, 0903973, and 0955825. The computations are held at Teragrid TG-MCA08X009 and the Georgia Tech FoRCE cluster.
Funding AgencyGrant Number
NASA Hubble Fellowship grantHST-HF-51298.01
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Subject Keywords: accretion, accretion disks; black hole physics; gravitational waves; hydrodynamics; relativistic processes; shock waves; X-rays: bursts
Issue or Number:2
Record Number:CaltechAUTHORS:20120515-114850932
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Official Citation: Tidal Disruptions of White Dwarfs from Ultra-close Encounters with Intermediate-mass Spinning Black Holes Roland Haas et al. 2012 ApJ 749 117
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:31472
Deposited By: Ruth Sustaita
Deposited On:15 May 2012 21:22
Last Modified:03 Oct 2019 03:52

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