X-ray emission from single Wolf-Rayet stars

TL;DR

This review summarizes current knowledge on X-ray emissions from single Wolf-Rayet stars, highlighting their modest luminosities, spectral characteristics, variability, and the need for further understanding of X-ray production mechanisms.

Contribution

It compiles and summarizes existing observations and theories about X-ray emissions from single Wolf-Rayet stars, emphasizing gaps in understanding and future research directions.

Findings

Wolf-Rayet stars have modest X-ray luminosities.

X-ray spectra show thermal plasma at tens of MK.

Some WN stars exhibit X-ray variability.

Abstract

This review briefly summarizes our knowledge of the X-ray emission from single WN, WC, and WO stars. These stars have relatively modest X-ray luminosities, typically not exceeding L_sun. The analysis of X-ray spectra usually reveals thermal plasma with temperatures reaching a few 10 MK. X-ray variability is detected in some WN stars. At present we don't fully understand how X-ray radiation in produced in WR stars, albeit there are some promising research avenues, such as the presence of CIRs in the winds of some stars. To fully understand WR stars we need to unravel mechanisms of X-ray production in their winds.