Modeling of non-stationary accretion disks in X-ray novae A 0620–00 and GRS 1124–68 during outburst

¹ Institute for Astronomy and Astrophysics, Kepler Center for Astro and Particle Physics, Eberhard Karls University, Sand 1, 72076 Tübingen, Germany e-mail: suleimanov@astro.uni-tuebingen.de
² Kazan State University, Kremlevskaja str., 18, Kazan 420008, Russia
³ Sternberg Astronomical Institute, Moscow State University, Universitetskij pr., 13, 119992, Moscow, Russia e-mail: [galja;shakura]@sai.msu.ru

Received: 7 May 2008
Accepted: 7 September 2008

Abstract

Aims. We address the task of modeling soft X-ray and optical light curves of X-ray novae in the high/soft state.

Methods. The analytic model of viscous evolution of an externally truncated accretion α-disk is used. Relativistic effects near a Kerr black hole and self-irradiation of an accretion disk are taken into account.

Results. The model is applied to the outbursts of X-ray nova Monocerotis 1975 (A 0620-00) and X-ray nova Muscae 1991 (GRS 1124-68). Comparison of observational data with the model yields constraints on the angular momentum (the Kerr parameter) of the black holes in A 0620-00 and GRS 1124-68: and ≤0.4, and on the viscosity parameter α of the disks: and . We also conclude that the accretion disks should have an effective geometrical thickness times greater than the theoretical value of the distance between the photometric layers.