The Nature of X-ray Sources in Nearby Starburst Galaxies




Palmore, David

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Images of nearby starburst galaxies taken with the Chandra X-ray Observatory (CXO) reveal bright X-ray sources, many of which are believed to be high mass X-ray binaries (HMXBs), formed during recent star formation. A HMXB is a star system that emits strong in the X-ray, usually a massive star and a compact object like a BH or NS. We found 49 HMXB candidates in six nearby starburst galaxies, based on 14 observations from the CXO. While the individual analyses from such galaxies lack statistical significance to produce unambiguous results on the nature and origin of HMXBs, combining the data from multiple starburst galaxies allows us to draw more solid conclusions about the HMXB population in galaxies of this type. For all X-ray sources, we determined their X-ray properties such as luminosity, X-ray counts, and hardness ratios. We utilized data from the Hubble Space Telescope to investigate the nature of these X-ray sources. We identified ~33 candidate donor stars to the HMXBs in the age range of 10-100 Myr. Six out of 49 XRBs are spatially coincident with young star clusters, and hence likely host BHs. Nearly half of the sources are located further than 100 pc from a cluster. Dynamical arguments and the results of N-body simulations suggest that these are likely NS-XRBs. The remaining sources are located less than 100 pc away from a cluster, and it is harder to assess if these are BH- or NS-binaries.





Palmore, D. C. (2022). <i>The nature of x-ray sources in nearby starburst galaxies</i> (Unpublished thesis). Texas State University, San Marcos, Texas.


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