Date of Award
Winter 3-21-2025
Degree Type
Thesis
Degree Name
Master of Science (MS)
Department
Physics
First Advisor
Anuj Sarma, PhD
Second Advisor
Jesus Pando, PhD
Abstract
X-ray binaries function as sources of potential energy that keep globular clusters from collapsing in on themselves, and therefore, understanding X-ray binaries is crucial to understanding globular clusters, and our galaxy as a whole. The dense cores of globular clusters can prevent both optical photometry and infrared photometry from adequately measuring the brightness of individual stars. However, the cores of globular clusters are much less crowded in the ultraviolet, which allows for the identification of individual stars within the core. By identifying ultraviolet counterparts to each X-ray source within a globular cluster, the type of X-ray emitter can be determined. I report the positions, magnitudes, X-ray luminosities, and object types of 69 candidate ultraviolet counterparts, including 4 low-mass X-ray binaries (LMXBs), 31 cataclysmic variables (CVs), 26 active binaries (ABs), 4 pulsars, and 2 X-asymptotic giant branch stars (X-AGBs), to Chandra X-ray Observatory sources, taken from the CSCView application, for 14 different globular clusters. Photometry was performed on UV275 and NUV336 HST UVIS data from MAST using DOLPHOT. Drizzled images created with the Astrodrizzle Python package were used as reference images and finding charts. After calculating the magnitudes, the positions of the ultraviolet detections were compared with the positions of Chandra X-ray sources. The colors of any ultraviolet detections that fell within the error circle of an X-ray detection were compared to the main sequence on a color magnitude diagram. Ultraviolet detections that fall above the main sequence were marked as ABs. Ultraviolet detections bluer than the main sequence were further analyzed using an X-ray hardness-luminosity diagram to determine if they were LMXBs, CVs, or pulsars. By setting a lower limit on X-ray luminosity, the relationship between the number of X-ray sources within a cluster and the stellar encounter rate of that cluster can be analyzed. The relationship shows that active binaries form primordially within globular clusters, whereas cataclysmic variables and low-mass X-ray binaries form dynamically, which confirms the findings of previous studies.
Recommended Citation
Schuster, William, "IDENTIFICATION OF CANDIDATE ULTRAVIOLET COUNTERPARTS TO GLOBULAR CLUSTER X-RAY BINARIES" (2025). College of Science and Health Theses and Dissertations. 613.
https://via.library.depaul.edu/csh_etd/613
SLP Collection
no