X-ray emission from single Wolf-Rayet stars
  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. 
Lidia Oskinova
astro-ph.SR