X-ray from Wolf-Rayet Stars
Ignace, R.; Oskinova, L., Pollock, A. M., Brown, J. C., Hamann, W.-R.
AA(U of Wisconsin), AB(University of Potsdam), AC(ESA/Vilspa), AD(University of Glasgow), AE(University of Potsdam)
We describe observations of several apparently single Wolf-Rayet stars that have now been observed with the XMM-Newton instrument. Prior to this, the X-ray data of Wolf-Rayet stars consisted primarily of ROSAT passband detections (many of which were marginal). Data for the nitrogen-rich stars WR 6 (EZ CMa; HD50896) and WR 110 have been described by Skinner etal, who unexpectedly found a hard component in the spectra. We report on a third WN star, WR 1, which also shows the hint of a hard tail. In our program we also observed the carbon-rich star WR 114. Even after 19000 seconds of integration, we were unable to detect this star, which places a 1-sigma upper limit to the ratio of X-ray to Bolometric luminosity of 10-8.4, about 25 times smaller than typical O stars. (This research has been supported by NASA grant NAG5-12557.)