Binary black hole accretion from a circumbinary disk: Gas dynamics inside the central cavity

Brian D. Farris, Paul Duffell, Andrew I. Macfadyen, Zoltan Haiman

    Research output: Contribution to journalArticlepeer-review

    Abstract

    We present the results of two-dimensional (2D) hydrodynamical simulations of circumbinary disk accretion using the finite-volume code DISCO. This code solves the 2D viscous Navier-Stokes equations on a high-resolution moving mesh which shears with the fluid flow, greatly reducing advection errors in comparison with a fixed grid. We perform a series of simulations for binary mass ratios in the range 0.026 ≤ q ≤ 1.0, each lasting longer than a viscous time so that we reach a quasi-steady accretion state. In each case, we find that gas is efficiently stripped from the inner edge of the circumbinary disk and enters the cavity along accretion streams, which feed persistent "mini disks" surrounding each black hole. We find that for q ≳ 0.1, the binary excites eccentricity in the inner region of the circumbinary disk, creating an overdense lump which gives rise to enhanced periodicity in the accretion rate. The dependence of the periodicity on mass ratio may provide a method for observationally inferring mass ratios from measurements of the accretion rate. We also find that for all mass ratios studied, the magnitude of the accretion onto the secondary is sufficient to drive the binary toward larger mass ratio. This suggests a mechanism for biasing mass-ratio distributions toward equal mass.

    Original languageEnglish (US)
    Article number134
    JournalAstrophysical Journal
    Volume783
    Issue number2
    DOIs
    StatePublished - Mar 10 2014

    Keywords

    • accretion, accretion disks
    • black hole physics

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

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