Astronomy and Astrophysics – Astrophysics
Scientific paper
Nov 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005phdt.........7z&link_type=abstract
PhD dissertation. Proquest Dissertations And Theses 2005. Section 0278, Part 0606 106 pages; [Ph.D. dissertation].United State
Astronomy and Astrophysics
Astrophysics
13
Relativistic Astrophysics, Black Holes, X-Ray Astronomy, X-Ray Binaries, General Relativity
Scientific paper
Black holes and Einstein's theories of relativity (especially general relativity) are closely related. Black holes provide the ultimate laboratory for testing general relativity because the strong gravitational fields, in which the general relativistic effects dominate, only exist in the vicinity of black holes and neutron stars. The accretion to black holes is believed to be the engine for AGNs and black hole X-ray binaries (BHXBs). To study black holes and their roles in the host systems (binaries or galaxies), we need to consider relativistic effects. This dissertation is mainly on the relativistic effects on the radiation from accretion disks around black holes; the relativistic effects on the spectral/temporal properties of individual sources; and the impact on the collective characteristics.
A ray-tracing method is used to calculate the transfer function, in the form of relativistically modified line profiles from annuli on a standard thin disk around a rotating black hole. This transfer function is then used to study the relativistic modification on continuum spectra from the disk, on broadening of absorption edges, on the Quasi-Periodic Oscillations (QPOs) properties in X-ray binary systems, and on the inclination angle distribution of known BHXBs. A new method of deriving the spectral hardening factor on the disk from the data is applied to three ASCA observations for the microquasar GRO J1G55-40, and then the derived spectral hardening factor is used to estimate the angular momentum of the central black hole in this source.
We conclude that (1) a simple disk precession model with relativistic effects can account for the QPO phase-lag transition and the energy dependency of QPO amplitude, as observed in the microquasar GRS 1915+105; (2) the spectral hardening factor is not a constant, but the inner disk radius of GRO J1655-40 is consistent with being a constant; after the color correction, the multi- color-disk (MCD) model with relativistic correction can give a good estimate on the angular momentum of the black hole in GRO J1655-40, and the estimated angular momentum is in the range 0.92 to 0.9999; (3) the observed BHXB inclination angle distribution rejects the Newtonian model, which is a clear indication of the strong gravity in these systems.
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