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Properties of Wolf-Rayet stars from X-ray to radio data

Published online by Cambridge University Press:  25 May 2016

Allan J. Willis
Allan J. Willis*
Affiliation:
Department of Physics & Astronomy, University College London, UK

Abstract

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This review outlines the impact of observations across the spectrum (X-rays to radio) on our understanding of the basic physical, chemical, wind and mass loss properties of Wolf-Rayet stars. Optical spectropolarimetry indicates that ∼ 15% of the WR stars have anisotropic winds, whilst the majority have globally spherically symmetric outflows. All WR stars probably have winds structured (clumped) on the smaller scale as evidenced from: thermal radio spectral indices, optical-UV continuum/line/polarisation variablity and time-series spectroscopy, and the ubiquity of wind X-ray emission. ROSAT results indicate LX(WR) = 1031–33 ergs−1 with kT ≃ 0.3keV. WR mass loss rates may be lower than previously thought: mean, clumping-corrected rates from radio data yield M(WN) ≃ 3 × 10−5 M⊙ yr−1 and M(WC) ≃ 2 × 10−5 M⊙ yr−1. Analyses of UV-optical-IR spectra lead to good constraints on Teff and L/L⊙ and confirm the chemical separation of the WN and WC classes: WN stars show H-He-C-N abundances reflecting CNO-burning products, and WC(WO) stars show He-burning products. ISO data are confirming the H-deficiency of WC winds, and reveal a substantially enhanced Neon abundance in WC stars.

Type
Part 1. Basic observational properties of Wolf-Rayet stars and other hot massive stars
Information
Symposium - International Astronomical Union , Volume 193: Wolf-Rayet Phenomena in Massive Stars and Starburst Galaxies , 1999 , pp. 1 - 12
Copyright
Copyright © Astronomical Society of the Pacific 1999 

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