2013MNRAS.436...71V

We study the observational signatures of the relativistic slim disc of 10M_☉ black hole, in a wide range of mass accretion rate, \skew2{dot}m, dimensionless spin parameter, a*, and viewing angle, i. In general, the innermost temperature, Tin, increases with the increase of i for a fixed value of \skew2{dot}m and a*, due to the Doppler effect. However, for i > 50° and \skew2{dot}m>\skew2{dot}m_turn, Tin starts to decrease with the increase of \skew2{dot}m. This is a result of self-obscuration - the radiation from the innermost hot part of the disc is blocked by the surrounding cooler part. The value of \skew2{dot}m_turn and the corresponding luminosities depend on a* and i. Such obscuration effects cause an interesting behaviour on the disc luminosity (Ldisc)-Tin plane for high inclinations. In addition to the standard disc branch which appears below \skew2{dot}m_turn and which obeys L_disc ∝T_in^4 relation, another branch above \skew2{dot}m_turn, which is nearly horizontal, may be observed at luminosities close to the Eddington luminosity. We show that these features are likely observed in a Galactic X-ray source, GRS 1915+105. We support a high spin parameter (a* > 0.9) for GRS 1915+105 since otherwise the high value of Tin and small size of the emitting region (rin < 1rS) cannot be explained.