Publication Date:
2013-10-29
Description:
We study the observational signatures of the relativistic slim disc of 10 M 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, T in , 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 $\skew2\dot{m} 〉 \skew2\dot{m}_{\rm turn}$ , T in 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 $\skew2\dot{m}_{\rm turn}$ and the corresponding luminosities depend on a * and i . Such obscuration effects cause an interesting behaviour on the disc luminosity ( L disc )– T in plane for high inclinations. In addition to the standard disc branch which appears below $\skew2\dot{m}_{\rm turn}$ and which obeys $L_{\rm disc} \propto T_{\rm in}^{4}$ relation, another branch above $\skew2\dot{m}_{\rm turn}$ , 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 T in and small size of the emitting region ( r in 〈 1 r S ) cannot be explained.
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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