Doctor of Philosophy (PhD)
Department of Physics and Astronomy
Using Rossi X-Ray Timing Explorer and Otto Struve Telescope data of low mass X-ray binaries (LMXBs) Cyg X-2 and Sco X-1, the optical regime’s relationship to the X-ray was investigated through several angles. Discrete cross correlations using the optical and X-ray data revealed evidence of reprocessing in both datasets. These were more consistently present in Sco X-1, where both small and obvious features were seen at less than 4 s of optical lag. The size of these lags makes it likely that most of the reprocessing is taking place on the accretion disk. Parameterization of the Z tracks led to distinct behaviors of the optical flux with respect to Z track location. The Sco X-1 optical flux increased in steps from the horizontal to the flaring branch, with a correlation present on the upper half of the latter. The Cyg X-2 datasets could be divided into two behaviors: a multivalued (horizontal and normal branches)/correlated state (flaring branch), and an uncorrelated state. A timed spectral study was used to examine how physical behaviors of the systems changed with optical intensity. A model consisting of a blackbody, a cutoff power law, a Gaussian, and an absorption coefficient was used. The optical correlates better with the Z track location than it does with any individual parameter in Sco X-1 and Cyg X-2.
Finally, JWST/MIRISim models were used to test a reduction pipeline designed to maximize the time resolution of incoming slitless spectroscopic data for planned observations of black hole LMXBs. Power law and custom spectral energy distributions based on WISE observations of the black hole GX 339-4 were reduced with both full integrations and with two group ramp fits. It was found that the scatter of power law index fits increased as the brightness decreased, and that when the brightness got low enough, the average fitted index began to increase (with respect to frequency). These effects were larger for the two group reductions. However, as GX 339-4 would be studied during outburst, it is likely that the latter behavior would be a small effect, as the system would be bright.
Igl, Alexander B., "Connecting the Optical Regime to the X-ray in Neutron Star Low Mass X-ray Binaries" (2023). LSU Doctoral Dissertations. 6235.