Doctor of Philosophy (PhD)


Physics and Astronomy

Document Type



The Chandra Galactic Bulge Survey (GBS) undertakes to find and classify X-ray sources in the Galactic Bulge. Of these X-ray sources, there is likely a significant minority which are Low Mass X-ray Binaries: systems containing either a neutron star or black hole that is accreting matter from a roughly stellar mass companion via Roche-Lobe overflow. I use optical time-series photometry from the Mosaic-II instrument on the Blanco 4m telescope at the Cerro Tololo Inter-American Observatory to identify counterparts to new X-ray sources in the GBS. Of those that are variable in brightness, I use the morphology of the changes and the relative proportion of optical and X-ray light, to identify high inclination systems through eclipses, to determine what periodicity, if any, is present in the optical light, and use these properties to partially or fully classify X-ray sources. The GBS contains a variety of X-ray sources, including Low Mass X-ray Binaries, Cataclysmic Variables, Intermediate Polars, Active Galactic Nuclei, W Ursa Ma joris stars, RS Canum Venaticorum stars, active stars, and flare stars. Spectroscopy greatly aids the classification of the X-ray source and is used, where available, to distinguish between source types and identify promising ob jects for further study. Only a handful of sources are identified as potential new Low Mass X-ray Binaries in quiescence, which places limits on the number of such systems in the Galaxy and on their outburst duty cycle. In addition to the GBS, I have done work on echo-tomography of Scorpius X-1, the brightest extra-solar X-ray source in the sky. I have found that reprocessing is dominated by the accretion disk in all observations, and that the companion is not reliably distinguishable in reprocessing of continuum light. I also found that reprocessing mainly occurs in the Flaring Branch of the Z-diagram, turning off in other X-ray states.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Hynes, Robert