X-ray binaries are among the most interesting Galactic objects. They consist of a neutron star or a black hole accreting material from a binary Companion star. They exhibit variability on timescales from milliseconds to years. Our research programme involves Low Mass X-ray Binaries, Black Hole Binaries and Galactic Jet sources. Work on LMXB includes the dipping, Z-track and Atoll classes, with the general aim of understanding the X-ray emission at a basic level. Strong variations in X-ray intensity (so called dips) are seen at the orbital period (typically a few hours), in the Low Mass X-ray Binary Dipping Sources when the X-ray source is obscured by the bulge in the outer accretiion disc where the accretion flow from the companion impacts. Strong spectral changes in the X-ray continuum are associated with this variability providing us with a powerful tool to study the nature, structure, geometry and properties of the X-ray emitting regions, particularly of the accretion disc corona: the major X-ray emitter. The aim of the work is now focussed on obtaining an understanding of the most fundamental aspects of LMXB: the reasons for the observed behaviour of the brightest, super-Eddington Z-track sources and of the majority of LMXB which are of the Atoll-type having luminosities between 10^36 erg/s and the Eddington limit. This very basic aim encompasses study of the three branches of the Z-track sources, in one of which radio observations prove the existence of jets (v/c = 0.45) and of unstable nuclear burning in these sources in comparison with the theory of unstable burning. Another important aspect is the common behaviour of many Atoll sources in X-ray bursting in which the X-ray emission increases 20 times in one second by unstable nuclear burning. Our work has led to an explanation of jet formation in Z-track and Atoll sources in which radiation pressure is an important factor. Finally we make simultaneous studies of the important QPO: quasi-periodic kHz oscillations in these sources and have proposed that the observed variations are also consistent with high radiation pressure.
PhD projects can be available in any of the above areas.
Research is actively carried out in this field using our proprietary or archival data from the observatories XTE, ASCA, SAX, XMM-Newton, Chandra and Suzaku. These provide the most advanced technology in X-ray Astronomy and high quality scientific data with full spectral and timing information. Data analysis is usually carried at the Astronomical Observatory of the Jagiellonian University.
Work abroad may be required for further analysis and in connection with our collaborations such as with the University of Palermo. For further details contact the supervisors: M. Balucinska-Church (mbc@star.sr.bham.ac.uk) or M. J. Church (mjc@star.sr.bham.ac.uk).
Last update on 19th June 2008