The X-ray Radiation From The Magnetized Black Hole-Accretion Disc System

The fast-spinning black hole (BH) is a huge energy reservoir, which can be regarded as an important energetic source for powering some high-energy objects in the Universe. It is of great importance to research the high-energy radiation related to the spinning BH. Two mechanisms of extracting energy from a rotating BH are investigated in this dissertation, and the focus is placed on the relationship between the magnetic coupling (MC) process and the high-energy X-ray phenomena such as the steep emissivity index, high-frequency quasi periodic oscillations (HFQPO), the broad emission lines, and the non-thermal X-ray emission.In Chapter 1, we briefly introduce the three aspects involved in this dissertation, the BH, the BH accretion disk, and the X-ray astronomy. The introduction of BH includes a concise history of the BH theory, two peculiar features of the BH, three classifications of the BH in astrophysics, and four mechanisms of extracting energy from it. Then we review the theories of accretion disks and the models of disk corona. At last, we present the development of the X-ray astronomy.In Chapter 2, the theories of magnetosphere and equivalent circuit are given in detail. The model of the coexistence of the BZ and MC processes is constructed, in which the BZ and MC powers are derived. This chapter is the theoretical basis of the Dissertation, which is closely related to the application of our model.Although our model has been used to explain the energetic gamma-ray bursts and jets, we devote this paper to the application in X-ray observations: We discuss the influence of the MC process on the flux of the local thermal radiation in section 3.1. It is shown that the steep emissivity index that is too high for the standard accretion disk model can be explained by MC model. Other models that explain the steep emissivity index are compared, and it is shown that MC model is favored by the observations.Two similar analytic model of hotspot are proposed in Sec. 3.2 to explain HFQPO and HFQPO pairs observed by RXTE. There are two major contents involving the derivation of the MC power in the case of non-axisymmetric magnetic field and the calculation of the time-scale of the screw instability via inductance.Since broad emission lines are important probes in the X-ray astronomy, in Sec. 3.3, the influences of MC process on the profile of the lines are investigated after expounding the formation and calculation of the relativistic iron line profile.In order to explain the hard X-rays observed in the BH-disc systems, as well as to make our model more self-consistent, corona is introduced in Sec. 3.4. The issue of energy balances of the disc and corona are discussed, two semi-analytical formulae and the procedures of Monte Carlo simulation are presented, and the significance of the corona for our BZMC model is explained.In the last Chapter, we summarize the main results and point out the aspects that need to be improved.