Tidal disruption of white dwarfs by intermediate mass black holes

¹ Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332, USA
² Theoretical AstroPhysics Including Relativity, California Institute of Technology, Pasadena, CA 91125, USA
³ Department of Astronomy, University of Maryland, College Park, MD 20742-2421, USA
⁴ Hubble Fellow

Abstract

Modeling ultra-close encounters between a white dwarf and a spinning, intermediate mass black hole requires a full general relativistic treatment of gravity. This paper summarizes results from such a study. Our results show that the disruption process and prompt accretion of the debris strongly depend on the magnitude and orientation of the black hole spin. On the other hand, the late-time accretion onto the black hole follows the same decay, Ṁ ∝  t^−5/3, estimated from Newtonian gravity disruption studies. The spectrum of the fallback material peaks in the soft X-rays and sustains Eddington luminosity for 1–3 yrs after the disruption. The orientation of the black hole spin has also a profound effect on how the outflowing debris obscures the central region. The disruption produces a burst of gravitational radiation with characteristic frequencies of ∼3.2 Hz and strain amplitudes of ∼10⁻¹⁸ for galactic intermediate mass black holes.