Observational and evolutionary studies of neutron star X-ray binaries

Abstract

In this thesis, we present our observational and evolutionary studies of neutron stars in X-ray binary systems. A variety of topics are discussed, which are all related by a single scientific theme, namely, helping to set constraints on the mass-radius relation of neutron stars, and hence on their equations of state (EOS). In Chapter 1 we review the current neutron star masses M and radii R measurement techniques utilizing the X-ray observation of neutron stars in binaries. These techniques fall into two categories: timing and spectral analysis. In Chapter 2 we present our spectral and timing analysis of 4U 2129+47. We show that 4U 2129+47 might be in a hierarchical triple system. The source has been dropping into deeper quiescence during the last decade. The absence of the power-law hard tail in its X-ray spectrum make it a good candidate for measuring neutron star radius. In Chapter 3 we present our analysis of EXO 0748-676. We show that the previously reported narrow absorption lines are inconsistent with the detected high amplitude of the 552 Hz burst oscillations. In Chapter 4 we present our semi-numerical method of evaluating the significance of burst oscillations. With this method, we searched 1187 archived RXTE Type-I X-ray bursts for high frequency oscillation modes. In Chapter 5, we present our evolutionary study of the most massive neutron star that has been recently found: PSR J1614-2230. The study has been carried out with the recently developed star evolution code "MESA". We We have computed an extensive grid of binary evolution tracks to represent low- and intermediate-mass X-ray binaries (LMXBs and IMXBs). The general results will be presented in Chapter 6.