Astron. Astrophys. 348, L45-L48 (1999)

Letter to the Editor

An explanation of observed trends in the X-ray emission from single Wolf-Rayet stars

R. Ignace and L.M. Oskinova

University of Glasgow, Kelvin Bldg, Department of Physics and Astronomy, Glasgow, G12 8QQ, Scotland UK

Received 10 May 1999 / Accepted 14 July 1999

Abstract

The O and early B star winds show empirical correlations between X-ray () and Bolometric ( luminosity as well as wind properties such as wind momentum and wind kinetic energy. Wolf-Rayet stars do not. We discuss scaling relations to qualitatively explain this lack of correlation among the WR winds and to quantitatively reproduce the observed ratio of X-ray luminosities between the N-rich WN types and C-rich WC types. If (a) the filling factor of hot X-ray emitting gas varies as for stars of different mass loss and terminal speed and (b) the ambient Wolf-Rayet wind component is optically thick to the hot gas X-rays, then a lack of correlation between and wind parameters is to be expected. The emergent X-ray emission then depends only on factors relating to relative abundances and ionization. The observed ratio is consistent with our scaling analysis using typical WN and WC abundances.

Key words: stars: abundances stars: early-type stars: mass-loss stars: Wolf-Rayet X-rays: stars

Send offprint requests to: rico@astro.gla.ac.uk

This article contains no SIMBAD objects.

Contents

• 1. Introduction
• 2. Simple theory of X-rays from stellar winds
• 3. Application to observations
• 4. Discussion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: July 26, 1999
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