Testing slim-disk models on the thermal spectra of LMC X-3

• Published in: Astronomy and astrophysics (Berlin) Vol. 533; p. A67
• Main Authors: Straub, O., Bursa, M., Sa¸dowski, A., Steiner, J. F., Abramowicz, M. A., Kluźniak, W., McClintock, J. E., Narayan, R., Remillard, R. A.
• Format: Journal Article
• Language: English
• Published: Les Ulis EDP Sciences 01.09.2011
• Subjects: accretion; accretion disks; Astronomi, astrofysik och kosmologi; Astronomy; Astronomy, Astrophysics and Cosmology; black hole physics; Earth, ocean, space; Exact sciences and technology; X-rays: binaries; Accretion; X-rays: binaries; Black holes; Intensity; Accretion rate; Consistency; Binary X ray source; Cosmic x-ray sources; Luminosity; Spectral model; Accretion disks; Continuum; Advection; black hole physics; X-ray binary stars; Cosmology; Large Magellanic Cloud
• DOI: 10.1051/0004-6361/201117385
• ISSN: 0004-6361

Slim-disk models describe advective accretion flows at high luminosities, while reducing to the standard thin disk form in the low luminosity limit. We have developed a new spectral model, slimbb, within the framework of XSPEC, which describes fully relativistic slim-disk accretion and includes photon ray-tracing that starts from the disk photosphere, rather than the equatorial plane. We demonstrate the features of this model by applying it to RXTE spectra of the persistent black-hole X-ray binary LMC X-3. LMC X-3 has the virtues of exhibiting large intensity variations while maintaining itself in soft spectral states which are well described using accretion-disk models, making it an ideal candidate to test the aptness of slimbb. Our results demonstrate consistency between the low-luminosity (thin-disk) and high luminosity (slim-disk) regimes. The results also illustrate that advection alone does not solve the problem of the origin of the surprisingly soft high-luminosity spectra in LMC X-3. We show that X-ray continuum-fitting in the high accretion rate regime can powerfully test black-hole accretion disk models.