Measurements and Analysis of Helium-like Triplet Ratios in the X-Ray Spectra of O-Type Stars
Abstract
We discuss new methods of measuring and interpreting the forbidden-to-intercombination line ratios of helium-like triplets in the X-ray spectra of O-type stars, including accounting for the spatial distribution of the X-ray-emitting plasma and using the detailed photospheric UV spectrum. Measurements are made for four O stars using archival Chandra HETGS data. We assume an X-ray-emitting plasma spatially distributed in the wind above some minimum radius R0. We find minimum radii of formation typically in the range of 1.25<R0/R*<1.67, which is consistent with results obtained independently from line profile fits. We find no evidence for anomalously low f/i ratios, and we do not require the existence of X-ray-emitting plasmas at radii that are too small to generate sufficiently strong shocks.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- October 2006
- DOI:
- 10.1086/507147
- arXiv:
- arXiv:astro-ph/0606370
- Bibcode:
- 2006ApJ...650.1096L
- Keywords:
-
- Stars: Early-Type;
- Stars: Winds;
- Outflows;
- Techniques: Spectroscopic;
- Astrophysics
- E-Print:
- 52 pages, 24 figures. Accepted in ApJ