Application of a relativistic accretion disc model to X-ray spectra of LMC X-1 and GRO J1655-40

Marek Gierliński (Lead / Corresponding author), Andrzej Maciołek-Niedźwiecki, Ken Ebisawa

Research output: Contribution to journalArticle

66 Citations (Scopus)

Abstract

We present a general relativistic accretion disc model and its application to the soft-state X-ray spectra of black hole binaries. The model assumes a flat, optically thick disc around a rotating Kerr black hole. The disc locally radiates away the dissipated energy as a blackbody. Special and general relativistic effects influencing photons emitted by the disc are taken into account. The emerging spectrum, as seen by a distant observer, is parametrized by the black hole mass and spin, the accretion rate, the disc inclination angle and the inner disc radius. We fit the ASCA soft-state X-ray spectra of LMC X-1 and GRO J1655-40 by this model. 

We find that, having additional limits on the black hole mass and inclination angle from optical/UV observations, we can constrain the black hole spin from X-ray data. In LMC X-1 the constraint is weak, and we can only rule out the maximally rotating black hole. In GRO J1655-40 we can limit the spin much better, and we find 0.68 ≤ a ≤ 0.88. Accretion discs in both sources are radiation-pressure dominated. We do not find Compton reflection features in the spectra of any of these objects.

Original languageEnglish
Pages (from-to)1253-1265
Number of pages13
JournalMonthly Notices of the Royal Astronomical Society
Volume325
Issue number3
DOIs
Publication statusPublished - 11 Aug 2001

Keywords

  • Accretion, accretion discs
  • Relativity
  • Stars: Individual: GRO J1655-40
  • Stars: Individual: LMC X-1
  • X-rays: Stars

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