AbstractOur current theoretical and observational understandings of the accretion disks around Galactic black-holes are reviewed. Historically, a simple phenomenological accretion disk model has been used to interpret X-ray observations. Although such a phenomenological interpretation is still useful, high quality X-ray data from contemporary instruments allow us to test more realistic accretion disk models. In a simple and ideal case, the standard optically thick accretion disk model is successful to explain observations, such that the inner disk radius is constant at three times the Schwarzschild radius over large luminosity variations. However, when disk luminosity is close to or exceeds the Eddington luminosity, the standard disk model breaks, and we have to consider the “slim disk” solution in which radial energy advection is dominant. Recent observations of Ultra-luminous X-ray sources (ULXs), which may not be explained by the standard disk model, strongly suggest the slim disk solution. We compare theoretical X-ray spectra from the slim disk with observed X-ray spectra of ULXs. We have found that the slim disk model is successful to explain ULX spectra, in terms of the massive stellar black-holes with several tens of solar mass and the super-Eddington mass accretion rates. In order to explain the large luminosities (>1040ergss−1) of ULXs, “intermediate black-holes” (>100M⊙) are not required. Slim disks around massive stellar black-holes of up to several tens of solar mass would naturally explain the observed properties of ULXs.


    Access

    Check access

    Check availability in my library

    Order at Subito €


    Export, share and cite



    Title :

    X-ray observations of black-hole accretion disks


    Contributors:

    Published in:

    Advances in Space Research ; 38 , 12 ; 2862-2866


    Publication date :

    2006-06-26


    Size :

    5 pages




    Type of media :

    Article (Journal)


    Type of material :

    Electronic Resource


    Language :

    English




    X-ray observations of black-hole accretion disks

    Ebisawa, K. / Kawaguchi, T. / COSPAR | British Library Conference Proceedings | 2006


    X-ray observations of black-hole accretion disks

    Ebisawa, Ken | Online Contents | 2006


    Slim accretion disks around black holes

    Szuszkiewicz, E. / Czerny, B. / Abramowicz, M. A. | NTRS | 1988


    Slim accretion disks around black holes

    Szuszkiewicz, E. / Czerny, B. / Abramowicz, M.A. | Elsevier | 1988


    Relativistic emission lines from accretion disks around black holes

    Čadež, Andrej / Calvani, Massimo | Elsevier | 2005