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Mass and spin co-evolution during the alignment of a black hole in a warped accretion disc

Perego, A. ; Dotti, M. ; Colpi, M. ; Volonteri, M.

In: Monthly Notices of the Royal Astronomical Society, 2009, vol. 399, no. 4, p. 2249-2263

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    Title
    • Mass and spin co-evolution during the alignment of a black hole in a warped accretion disc
    Author
    • Perego, A.. Department of Physics, University of Basel, Klingelbergstr. 82, 4056 Basel, Switzerland
    • Dotti, M.. Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA
    • Colpi, M.. Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Piazza Della Scienza 3, 20126 Milano, Italy
    • Volonteri, M.. Department of Astronomy, University of Michigan, Ann Arbor, MI 48109, USA
    Document Type
    • Postprint
    OAI-PMH Identifier
    • oai:doc.rero.ch:293624
    Summary
    In this paper, we explore the gravitomagnetic interaction of a black hole (BH) with a misaligned accretion disc to study BH spin precession and alignment jointly with BH mass MBH and spin parameter a evolution, under the assumption that the disc is continually fed, in its outer region, by matter with angular momentum fixed on a given direction . We develop an iterative scheme based on the adiabatic approximation to study the BH-disc co-evolution: in this approach, the accretion disc transits through a sequence of quasi-steady warped states (Bardeen-Petterson effect) and interacts with the BH until the spin JBH aligns with . For a BH aligning with a corotating disc, the fractional increase in mass is typically less than a few per cent, while the spin modulus can increase up to a few tens of per cent. The alignment time-scale is of ∼105-106 yr for a maximally rotating BH accreting at the Eddington rate. BH-disc alignment from an initially counter-rotating disc tends to be more efficient compared to the specular corotating case due to the asymmetry seeded in the Kerr metric: counter-rotating matter carries a larger and opposite angular momentum when crossing the innermost stable orbit, so that the spin modulus decreases faster and so the relative inclination angle