Roland Haas, Roman V. Shcherbakov, Tanja Bode, Pablo Laguna
We present numerical relativity results of tidal disruptions of white dwarfs
from ultra-close encounters with a spinning, intermediate mass black hole.
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 spin. However, the
late-time accretion onto the black hole follows the same decay, $\dot{M}$ ~
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 yrs after the disruption. For arbitrary black hole 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 intermediate mass black holes. The optimistic rate of
considered ultra-close disruptions is consistent with no sources found in ROSAT
all-sky survey. The future missions like Wide-Field X-ray Telescope (WFXT)
could observe dozens of events.
View original:
http://arxiv.org/abs/1201.4389
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