Wind-powered Ultraluminous X-ray Sources

Wiktorowicz, Grzegorz; Lasota, Jean-Pierre; Belczynski, Krzysztof; Lu, Youjun; Liu, Jifeng; Iłkiewicz, Krystian

Abstract

Although ultraluminous X-ray sources (ULX) are important for astrophysics because of their extreme apparent super-Eddington luminosities, their nature is still poorly known. Theoretical and observational studies suggest that ULXs could be a diversified group of objects that are composed of low-mass X-ray binaries, high-mass X-ray binaries and marginally also systems containing intermediate-mass black holes. Observational data on the ULX donors could significantly boost our understanding of these systems, but only a few have been detected. There are several candidates, mostly red supergiants (RSGs), but surveys are typically biased toward luminous near-infrared objects. In ULXs harbouring RSGs matter accreted onto the compact body would have to be provided by the stellar wind of the companion because a Roche-lobe overflow could be unstable for relevant mass-ratios. We present a comprehensive study of the evolution and population of wind-fed ULXs, and we provide a theoretical support for the link between RSGs and ULXs. Assuming a minimal model of stellar-wind emission, our estimated upper limit on contribution of wind-fed ULX to the overall ULX population is ∼75%–96% for young (<100 Myr) starforming environments, ∼49%–87% for prolonged constant star formation (e.g., disk of Milky Way), and 1% for environments in which star formation ceased long time (>2 Gyr) ago. We show also that some wind-fed ULXs (up to 6%) may evolve into merging double compact objects (DCOs). We demonstrate that the exclusion of wind-fed ULXs from population studies of ULXs might have lead to systematic errors in their conclusions.

Citation

Wiktorowicz, G., Lasota, J.-P., Belczynski, K., Lu, Y., Liu, J., & Iłkiewicz, K. (2021). Wind-powered Ultraluminous X-ray Sources. Astrophysical Journal, 918(2), Article 60. https://doi.org/10.3847/1538-4357/ac0cf7

• Journal Article Type: Article
• Acceptance Date: Jun 18, 2021
• Online Publication Date: Sep 8, 2021
• Publication Date: 2021
• Deposit Date: Oct 14, 2021
• Publicly Available Date: Oct 14, 2021
• Journal: Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 918
• Issue: 2
• Article Number: 60
• DOI: https://doi.org/10.3847/1538-4357/ac0cf7
• Public URL: https://durham-repository.worktribe.com/output/1227010