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This thesis presents a comprehensive investigation into the stellar populations and blue supergiant high-mass X-ray binaries (BSG-HMXBs) in the dwarf star-forming galaxy IC 10. The study is motivated by two primary objectives: firstly, to conduct a detailed analysis of the blue supergiant x-ray binary population in IC 10, and secondly, to explore the properties of IC 10 X-1, the brightest source in the galaxy, which is identified as a high mass x-ray binary containing a Wolf-Rayet and black hole. The dwarf galaxy in Cassiopeia, IC 10, located in “close” proximity of 660 kpc, captivates astronomers with its young stellar population, abundant Wolf-Rayet stars, and the presence of massive stars in general. Leveraging a series of space-based X-ray telescope (Chandra) observations, we have identified 375 X-ray point sources. Correlating our list of x-ray sources with published optical catalogs we found those having an optical counterpart. Applying an optical color-magnitude selection to isolate blue supergiant stars, we find the final list of intriguing blue supergiants in a compact-object(x-ray) binary. The ongoing starburst in IC 10 has given rise to a diverse collection of exotic compact-object binaries, including IC 10 X-1 (a Wolf-Rayet and Blackhole high mass x-ray binary) and IC 10 X-2 (a Blue supergiant fast x-ray transient). We have also used GEMINI/GMOS optical spectroscopy to enable multi-wavelength characterization of these BSG sources. Furthermore, our investigation into IC 10 X-1 reveals surprising findings regarding its X-ray emission and orbital dynamics. Through multi-wavelength analysis combining optical radial velocity (RV) curves and X-ray eclipse lightcurves, we uncover a quarter phase offset between these two observational features. IC 10 X-1 is a blackhole+Wolf-Rayet (BH+WR) high mass X-ray binary with an orbital period of 34.9 hrs. The BH mass is currently unconstrained, as the BH accretion disk irradiates the WR wind and alters the ionization structure of spectral line formation regions near the WR star. This alteration of the WR wind geometry masquerades as the classic binary RV curve. To understand the nature of this complex system, we perform a detailed multi-wavelength study using optical spectroscopy (GEMINI/GMOS), X-ray phase-resolved spectroscopy (Chandra), and x-ray lightcurve analysis (Chandra+Swift+XMM), aiming to elucidate the orbital period derivative and refine our understanding of the system’s binary parameters and physical nature. Blue SG-XRBs include a major class of progenitors of double-degenerate binaries, hence their numbers are an important factor in modeling the rate of gravitational-wave sources. Identifying the nature of individual sources is a slow and difficult process, but ultimately necessary as it paves the way toward a comprehensive census of X-ray binaries (XRBs), enabling meaningful comparisons with other galaxies, for example, the Magellanic Clouds.
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This content will become publicly available on December 1, 2026
Chandra Observations of the X-Ray Binary Population in the Field of the Dwarf Galaxy IC 10
IC 10 is a dwarf galaxy in Cassiopeia, located at a distance of 660 kpc, and hosts a young stellar population, a large number of Wolf–Rayet stars, and a large number of massive stars in general. Utilizing a series of 11 Chandra observations (spanning 2003–2021, with a total exposure of 235.1 ks), 375 point sources of X-ray emission were detected. Similar studies have been conducted earlier in the central region of IC 10. Here, we consider all regions covered by Chandra-ACIS. By comparing our catalog of X-ray sources with a published optical catalog, we found that 146 sources have optical counterparts. We also created a list of 60 blue supergiant (SG) candidates with X-ray binary (XRB) companions by using an optical color–magnitude selection criterion to isolate the blue SGs. Blue SG-XRBs form a major class of progenitors of double-degenerate binaries. Hence, their numbers are an important factor in modeling the rate of gravitational-wave sources. Identifying the nature of individual sources is necessary as it paves the way toward a comprehensive census of XRBs in IC 10, thus enabling meaningful comparisons with other Local Group galaxies exhibiting starbursts, such as the Magellanic Clouds.
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- Award ID(s):
- 2109004
- PAR ID:
- 10657605
- Publisher / Repository:
- MDPI
- Date Published:
- Journal Name:
- Astronomy
- Volume:
- 4
- Issue:
- 4
- ISSN:
- 2674-0346
- Page Range / eLocation ID:
- 26
- Subject(s) / Keyword(s):
- astrophysics
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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