Other
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aas...20913307c&link_type=abstract
2007 AAS/AAPT Joint Meeting, American Astronomical Society Meeting 209, #133.07; Bulletin of the American Astronomical Society,
Other
Scientific paper
The resolved x-ray emission line profiles of O stars carry a significant amount of information about the kinematics of the hot plasma in their massive stellar winds. They provide important clues to the x-ray production mechanism, and via the effects of continuum absorption, also place key constraints on conditions in the bulk, cool wind. Initial interpretations of the relatively symmetric form of observed profiles suggested significant mass-loss rate reductions, but recent studies argue that the profile shapes can be affected by wind clumping and the associated porosity, as well as by resonance scattering. We report here on the results of quantitative model fitting to several relatively high-resolution, high signal-to-noise Chandra and XMM-Newton spectra of O stars. We interpret the results of this analysis in light of recent adjustments to O star mass-loss rates based on the analysis of UV data and also in light of state-of-the-art 2D numerical simulations of the line-force instability. We show that reduced optical depth is statistically favored over porosity when high-quality data are quantitatively analyzed and that, in any case, porosity can only significantly affect line profile shapes when unrealistically large porosity scales are assumed. Further, we show that resonance scattering seems to be important in understanding the longer-wavelength oxygen and nitrogen lines in O stars with very dense winds, but is probably not significant for most other lines in the x-ray spectra of O stars or in hot stars with lower mass-loss rates.
We acknowledge support from grant AR5-6003X to Swarthmore College from the Chandra X-ray Center at the Smithsonian Astrophysical Observatory.
Cohen David H.
Leutenegger Maurice A.
Owocki Stanley P.
ud-Doula Asif
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