Minidisks in Binary Black Hole Accretion

Geoffrey Ryan, Andrew MacFadyen

    Research output: Contribution to journalArticle

    Abstract

    Newtonian simulations have demonstrated that accretion onto binary black holes produces accretion disks around each black hole ("minidisks"), fed by gas streams flowing through the circumbinary cavity from the surrounding circumbinary disk. We study the dynamics and radiation of an individual black hole minidisk using 2D hydrodynamical simulations performed with a new general relativistic version of the moving-mesh code Disco. We introduce a comoving energy variable that enables highly accurate integration of these high Mach number flows. Tidally induced spiral shock waves are excited in the disk and propagate through the innermost stable circular orbit, providing a Reynolds stress that causes efficient accretion by purely hydrodynamic means and producing a radiative signature brighter in hard X-rays than the Novikov-Thorne model. Disk cooling is provided by a local blackbody prescription that allows the disk to evolve self-consistently to a temperature profile where hydrodynamic heating is balanced by radiative cooling. We find that the spiral shock structure is in agreement with the relativistic dispersion relation for tightly wound linear waves. We measure the shock-induced dissipation and find outward angular momentum transport corresponding to an effective alpha parameter of order 0.01. We perform ray-tracing image calculations from the simulations to produce theoretical minidisk spectra and viewing-angle-dependent images for comparison with observations.

    Original languageEnglish (US)
    Article number199
    JournalAstrophysical Journal
    Volume835
    Issue number2
    DOIs
    StatePublished - Feb 1 2017

    Fingerprint

    accretion
    hydrodynamics
    cooling
    simulation
    shock
    ray tracing
    shock wave
    angular momentum
    temperature profile
    gas streams
    dissipation
    Reynolds stress
    circular orbits
    cavity
    Mach number
    accretion disks
    temperature profiles
    heating
    shock waves
    mesh

    Keywords

    • accretion, accretion disks
    • hydrodynamics
    • shock waves
    • stars: black holes

    ASJC Scopus subject areas

    • Astronomy and Astrophysics
    • Space and Planetary Science

    Cite this

    Minidisks in Binary Black Hole Accretion. / Ryan, Geoffrey; MacFadyen, Andrew.

    In: Astrophysical Journal, Vol. 835, No. 2, 199, 01.02.2017.

    Research output: Contribution to journalArticle

    Ryan, Geoffrey ; MacFadyen, Andrew. / Minidisks in Binary Black Hole Accretion. In: Astrophysical Journal. 2017 ; Vol. 835, No. 2.
    @article{50c689341c2c40a2b3f462e18e5df899,
    title = "Minidisks in Binary Black Hole Accretion",
    abstract = "Newtonian simulations have demonstrated that accretion onto binary black holes produces accretion disks around each black hole ({"}minidisks{"}), fed by gas streams flowing through the circumbinary cavity from the surrounding circumbinary disk. We study the dynamics and radiation of an individual black hole minidisk using 2D hydrodynamical simulations performed with a new general relativistic version of the moving-mesh code Disco. We introduce a comoving energy variable that enables highly accurate integration of these high Mach number flows. Tidally induced spiral shock waves are excited in the disk and propagate through the innermost stable circular orbit, providing a Reynolds stress that causes efficient accretion by purely hydrodynamic means and producing a radiative signature brighter in hard X-rays than the Novikov-Thorne model. Disk cooling is provided by a local blackbody prescription that allows the disk to evolve self-consistently to a temperature profile where hydrodynamic heating is balanced by radiative cooling. We find that the spiral shock structure is in agreement with the relativistic dispersion relation for tightly wound linear waves. We measure the shock-induced dissipation and find outward angular momentum transport corresponding to an effective alpha parameter of order 0.01. We perform ray-tracing image calculations from the simulations to produce theoretical minidisk spectra and viewing-angle-dependent images for comparison with observations.",
    keywords = "accretion, accretion disks, hydrodynamics, shock waves, stars: black holes",
    author = "Geoffrey Ryan and Andrew MacFadyen",
    year = "2017",
    month = "2",
    day = "1",
    doi = "10.3847/1538-4357/835/2/199",
    language = "English (US)",
    volume = "835",
    journal = "Astrophysical Journal",
    issn = "0004-637X",
    publisher = "IOP Publishing Ltd.",
    number = "2",

    }

    TY - JOUR

    T1 - Minidisks in Binary Black Hole Accretion

    AU - Ryan, Geoffrey

    AU - MacFadyen, Andrew

    PY - 2017/2/1

    Y1 - 2017/2/1

    N2 - Newtonian simulations have demonstrated that accretion onto binary black holes produces accretion disks around each black hole ("minidisks"), fed by gas streams flowing through the circumbinary cavity from the surrounding circumbinary disk. We study the dynamics and radiation of an individual black hole minidisk using 2D hydrodynamical simulations performed with a new general relativistic version of the moving-mesh code Disco. We introduce a comoving energy variable that enables highly accurate integration of these high Mach number flows. Tidally induced spiral shock waves are excited in the disk and propagate through the innermost stable circular orbit, providing a Reynolds stress that causes efficient accretion by purely hydrodynamic means and producing a radiative signature brighter in hard X-rays than the Novikov-Thorne model. Disk cooling is provided by a local blackbody prescription that allows the disk to evolve self-consistently to a temperature profile where hydrodynamic heating is balanced by radiative cooling. We find that the spiral shock structure is in agreement with the relativistic dispersion relation for tightly wound linear waves. We measure the shock-induced dissipation and find outward angular momentum transport corresponding to an effective alpha parameter of order 0.01. We perform ray-tracing image calculations from the simulations to produce theoretical minidisk spectra and viewing-angle-dependent images for comparison with observations.

    AB - Newtonian simulations have demonstrated that accretion onto binary black holes produces accretion disks around each black hole ("minidisks"), fed by gas streams flowing through the circumbinary cavity from the surrounding circumbinary disk. We study the dynamics and radiation of an individual black hole minidisk using 2D hydrodynamical simulations performed with a new general relativistic version of the moving-mesh code Disco. We introduce a comoving energy variable that enables highly accurate integration of these high Mach number flows. Tidally induced spiral shock waves are excited in the disk and propagate through the innermost stable circular orbit, providing a Reynolds stress that causes efficient accretion by purely hydrodynamic means and producing a radiative signature brighter in hard X-rays than the Novikov-Thorne model. Disk cooling is provided by a local blackbody prescription that allows the disk to evolve self-consistently to a temperature profile where hydrodynamic heating is balanced by radiative cooling. We find that the spiral shock structure is in agreement with the relativistic dispersion relation for tightly wound linear waves. We measure the shock-induced dissipation and find outward angular momentum transport corresponding to an effective alpha parameter of order 0.01. We perform ray-tracing image calculations from the simulations to produce theoretical minidisk spectra and viewing-angle-dependent images for comparison with observations.

    KW - accretion, accretion disks

    KW - hydrodynamics

    KW - shock waves

    KW - stars: black holes

    UR - http://www.scopus.com/inward/record.url?scp=85011984524&partnerID=8YFLogxK

    UR - http://www.scopus.com/inward/citedby.url?scp=85011984524&partnerID=8YFLogxK

    U2 - 10.3847/1538-4357/835/2/199

    DO - 10.3847/1538-4357/835/2/199

    M3 - Article

    VL - 835

    JO - Astrophysical Journal

    JF - Astrophysical Journal

    SN - 0004-637X

    IS - 2

    M1 - 199

    ER -