Classification of x-ray binary systems in selected spiral galaxies

In this thesis, the populations of X-ray binaries (XRBs) in the spiral galaxies NGC 1365 and NGC 4321 have been investigated. Candidate XRBs were identified through the analysis of archival data from the Chandra X-ray Observatory, and their potential optical and near-infrared counterparts were determined using data from the Hubble Space Telescope (HST) and the James Webb Space Telescope (JWST). In NGC 1365, a total of 63 candidate XRBs were found, with X-ray fluxes (FX) ranging from 8.61×10-16 to 7.54×10-13 erg s⁻¹ cm⁻², and X-ray luminosities (LX) ranging from 3.11×1037 to 2.72×1040 erg s⁻¹. Among these candidates, seven sources were found to have X-ray variability factor, Vf > 10. For four XRBs, the brightness of their potential counterparts in all filters used from HST and JWST observations was measured to be mF555W > 22 mag in the HST/F555W filter and mF200W > 17 mag in the JWST/F200W filter. Similarly, in NGC 4321, 101 candidate XRBs were identified, with FX ranging from 2.94×10-16 to 2.11×10-13 erg s⁻¹ cm⁻², and LX ranging from 7.22×1036 to 5.18×1039 erg s⁻¹. Additionally, 19 sources were found to have Vf >10. For 14 XRBs, the potential optical and near-infrared counterparts exhibited brightness values of mF555W > 21 mag and mF200W > 19 mag Color-magnitude diagrams (CMDs) were constructed using the HST filters F438W, F555W, and F814W. By employing Padova isochrones, the mass ranges for the optical counterparts were estimated to be 8–30 M☉ for NGC 1365 and 8–25 M☉ for NGC 4321. Based on these findings, the optical counterparts were classified as high-mass X-ray binaries (HMXBs). Keywords: X-ray Binaries, Galaxies, NGC 1365, NGC 4321.