EDP Sciences
Free access
Volume 372, Number 3, June IV 2001
Page(s) 963 - 980
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20010534

A&A 372, 963-980 (2001)
DOI: 10.1051/0004-6361:20010534

On the Baldwin effect of He II emission lines in WR (WN) stars

J. I. van Gent1, H. J. G. L. M. Lamers1, 2, A. de Koter3 and P. W. Morris4

1  Astronomical Institute, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands
2  SRON Laboratory for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
    e-mail: lamers@astro.uu.nl
3  Astronomical Institute "Anton Pannekoek" , University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
    e-mail: dekoter@astro.uva.nl
4  California Institute of Technology, SIRTF Science Center, M/C 100-22, Pasadena CA 91125, USA
    e-mail: pmorris@ipac.caltech.edu

(Received 24 July 2000 / Accepted 6 April 2001)

We investigate the relation between the equivalent width of He II emission lines and the monochromatic continuum luminosity at the line wavelength in the spectra of Wolf-Rayet stars. Model stellar atmospheres and spectra are used to show that the equivalent width inversely correlates with the monochromatic continuum luminosity. We find the effect in Wolf-Rayet star models over a large range of stellar parameters. The effect is shown to be connected to density differences among Wolf-Rayet star winds. The conclusion is drawn that the Baldwin effect may provide a new method for the determination of Wolf-Rayet star distances.

Key words: stars: atmospheres -- stars: emission line -- stars: Wolf-Rayet

Offprint request: J. van Gent, gent@astro.uu.nl

© ESO 2001