This thesis brings together the various techniques of X-ray spectral analysis in order to examine the properties of black holes that vary in mass by several orders of magnitude. In all these systems it is widely accepted that the X-ray emission is produced by Compton up-scattering of lower energy seed photons in a hot corona or accretion flow, and here these processes are examined through a study of the X-ray spectral variability of each source. A new technique is introduced, in which models are fitted to over 2 million X-ray spectra on time-scales as short as 16 ms, and subsequently it is shown that the nature of the correlation between intensity and spectral index is strongly dependent upon the spectral state of the black hole. Finally, the results of an extensive survey of nearby galactic nuclei using the Chandra X-ray telescope are presented in the form of images and spectra, and these results are used along with data from the literature to search for Compton-thick nuclei.

The one-stop general book on the whole of X-ray astronomy.

This volume extends the ISSI series on magnetic fields in the Universe into the domain of what are by far the strongest fields in the Universe, and stronger than any field that could be produced on Earth. The chapters describe the magnetic fields in non-degenerate strongly magnetized stars, in degenerate stars (such as white dwarfs and neutron stars), exotic members called magnetars, and in their environments, as well as magnetic fields in the environments of black holes. These strong fields have a profound effect on the behavior of matter, visible in particular in highly variable processes like radiation in all known wavelengths, including Gamma-Ray bursts. The generation and structure of such strong magnetic fields and effects on the environment are also described.

X-ray binaries are some of the most varied and perplexing systems known to astronomers. The compact object which accretes mass from its companion star may be a white dwarf, neutron star, or black hole, whereas the donor star can be a 'normal' star or a white dwarf. The various combinations differ widely in their behaviour, and this timely volume provides a unique reference of our knowledge to date of all of them.Fifteen specially written chapters by a team of the world's foremost researchers in the field explore all aspects of the X-ray binaries. They cover the X-ray, ultraviolet, optical and radio properties of these violent systems and address key issues such as: how were these systems formed, and what will be their fate; how can we understand X-ray bursts, and how the quasi-periodic oscillations; what is the connection between millisecond radio pulsars and low-mass X-ray binaries; and how does the magnetic field of a neutron star decay?This long awaited review provides graduate students and researchers with the standard reference on X-ray binaries for many years to come.

On May 18-21, 2004, the Max-Planck-Society’s Harnack-Haus in Dahlem, Berlin hosted the international symposium "Exploring the Cosmic Frontier: Astrophysical Instruments for the 21st Century". The symposium was dedicated to exploring the complementarity and synergies between different branches of astrophysical research, by presenting and discussing the fundamental scientific problems that will be addressed in the next few decades.

A collection of papers using the relative advantages of studying stellar mass and supermassive black holes. The topics discussed here include the state of the art in black hole observational and theoretical work-variability, spectroscopy, disk-jet connections, and multi-wavelength campaigns on black holes.