AAS 195th Meeting, January 2000
Session 50. Stellar Atmospheres
Display, Thursday, January 13, 2000, 9:20am-6:30pm, Grand Hall

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[50.10] A Tailored Analysis of the WR stars WR40 and WR16 (WN8)

J.E. Herald, D.J. Hillier, R.E. Schulte-Ladbeck (University of Pittsburgh)

We present the results of tailored spectral analyses of a pair of WN8 stars - WR40 (HD 96548) and WR16 (HD 86161). Utilizing ``state-of-the-art'' stellar atmospheres code, improved stellar parameters are obtained by comparing synthetic spectra with observations over the wavelength range of 1100 to 20000\,Å. For WR40, this range is extended down to 900\,Å\ with the addition of far-UV HUT data. We apply the effects of interstellar \ion{H}{1} and H2 absorption, which strongly influence this region, to the model spectrum and deduce their respective column densities.

The optical spectra of WR40 & WR16 are dominated by hydrogen, helium and nitrogen emission lines, which previous models have been unable to reproduce simultaneously. Recent enhancements to our code, which account for wind inhomogeneities and the effects of line-blanketing, are seen to alleviate many of these discrepancies. Additionally, our detailed treatment of iron is given a rugged test in duplicating the rich Fe{\, \sc iv}-{\sc v} dominated UV region. Important line complexes of the UV are identified, and the abundances of iron as well as other metals are determined. We deduce reddening parameters towards both objects by analyzing their entire spectra, and find the reddening to be anomalous towards WR40. Our derived stellar parameters indicate the WN8 stars to be hotter than previously thought, while their winds possess a degree of inhomogeneity which leads to significantly lower mass-loss rates. We conclude by discussing the implications of our findings for the understanding of massive star evolution.

This project has been funded by NASA/\emph{Astro}-2 award NAG8-1073.

The author(s) of this abstract have provided an email address for comments about the abstract: jim@phyast.pitt.edu

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