High Resolution X-ray Spec- tra of WR 6
As WR 6 is a putatively single WN4 star, and is relatively bright (V = 6.9), it is an ideal case for studying the wind mechanisms in these extremely luminous stars. To obtain higher resolution spectra at higher energy (above 1 keV) than previously obtained with the XMM/Newton RGS, we have observed WR 6 with the Chandra High Energy Transmission Grating Spectrometer for 450 ks. We have resolved emission lines of S, Si, Mg, Ne, and Fe, which all show a “fin”-shaped profile, characteristic of a self-absorbed uniformly expanding shell. Steep blue edges gives robust maximal expansion velocities of about 2000 km/s, somewhat larger than the 1700 km/s derived from UV lines. The He-like lines all indicate that X-ray emitting plasmas are far from the photosphere – even at the higher energies where opacity is lowest – as was also the case for the longer wavelength lines observed with XMM-Newton/RGS. Abundances determined from X-ray spectral modeling indicate enhancements consistent with nucleosynthesis. The star was also variable in X-rays and in simultaneous optical photometry obtained with Chandra aspect camera, but not coherently with the optically known period of 3.765 days.
Huenemoerder, David; Gayley, K.; Hamann, Wolf-Rainer; Ignace, Richard; Nichols, J.; Oskinova, Lidia M.; Pollock, A. M.T.; and Schulz, N.. 2015. High Resolution X-ray Spec- tra of WR 6. Proceedings of an International Workshop held in Potsdam, Germany. https://nbn-resolving.org/urn:nbn:de:kobv:517-opus4-88236