Multi-periodic variability in low mass x-ray binaries

Thesis

An introduction is given to the fields of low mass X-ray binaries (LMXBs), soft X-ray transients (SXTs) and related classes of objects. Aspects such as evolution, variability and populations are reviewed.

The methods of time series analysis are listed and the new method of Bayesian spectrum analysis and parameter estimation is outlined. In particular the methods required to analyze multi-periodic variability in LMXB light curves are described, as used in subsequent chapters. Artificial datasets are used to examine the robustness of the Bayesian frequency analysis methods. An ad hoc method of deconvolving the effects of data sampling is then detailed.

The optical variability of V404 Cyg is analyzed using the methods of the preceding chapter. Orbital and short period variations are examined in several wavebands and the implications for this black-hole candidate discussed. Models for the short period variation are compared to the observed behaviour, to locate the origin of this effect. Modelling of ellipsoidal variability in V404 Cyg, J0422+32 and several faint X-ray transients allows the determination of the inclination for these systems. Other important physical parameters are also considered and compared to previous values cited in the literature.

The globular cluster LMXB AC211 is then examined to try to shed some light on the complex orbital variability observed. Several photometric and spectroscopic datasets are combined to provide an overall, relative probability for the two possible periods.

The distributions of neutron star and black-hole masses are analyzed to provide constraints on models of the neutron star equation of state. Inclinations obtained from ellipsoidal analysis and the excess noise seen in SXT light curves, are discussed.

Authors: Martin, A; Martin, Andrew

• Publication date: 1995
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Subjects: X-ray binaries