Journal Article

A comparative analysis of standard accretion discs spectra: an application to ultraluminous X-ray sources

A. Lorenzin and L. Zampieri

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 394, issue 3, pages 1588-1596
Published in print April 2009 | ISSN: 0035-8711
Published online April 2009 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.14435.x
A comparative analysis of standard accretion discs spectra: an application to ultraluminous X-ray sources

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We compare standard models of accretion discs around black holes (BHs) that include the appropriate zero-torque inner boundary condition and relativistic effects on the emission and propagation of radiation. The comparison is performed adopting the multicolour disc blackbody model (MCD) as reference and looking for the parameter space in which it is in statistical agreement with ‘more physical’ accretion disc models. We find simple ‘recipes’ that can be used for adjusting the estimates of the physical inner radius of the disc, the BH mass and the accretion rate inferred using the parameters of the MCD fits. We applied these results to four ultraluminous X-ray sources for which MCD spectral fits of their X-ray soft spectral components have been published and find that, in three cases (NGC 1313 X-1, X-2 and M 81 X-9), the BH masses inferred for a standard disc around a Schwarzschild BH are in the interval ∼100–200 M. Only if the BH is maximally rotating are the masses comparable to the much larger values previously derived in the literature.

Keywords: accretion, accretion discs; black hole physics; X-rays: binaries

Journal Article.  6922 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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