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Wolf-Rayet Stars

Wolf-Rayet Stars Wolf-Rayet (W-R) stars are hot, luminous objects with strong, broad ( '" 103 km s -I ) emission lines in the optical region ( 189) due to a substantial stellar wind. The W-R phase is a normal stage of evolution for all stars initially more massive than ",40 M0' and these extreme Population I stars are the topic of this review. A W-R phase is also present in some central stars of planetary nebulae, which we do not discuss here. Some 160 indi­ vidual stars of this class are known in our own Galaxy, and many others have been identified among galaxies of the Local Group. W-R stars come in two major subtypes (22): the WN, in which lines of helium and nitrogen ions are seen; and the we, which contain lines of carbon and oxygen along with the helium ions. An additional minor subtype (WO) with strong 0 VI lines has also recently been identified ( 19). The main characteristic of the optical spectrum of W-R stars is the dominance of emission lines. In a few WN stars, hydrogen appears to be present (52, 159), but generally the spectra of W-R stars are notable for the absence http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Annual Review of Astronomy and Astrophysics Annual Reviews

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References (2)

Publisher
Annual Reviews
Copyright
Copyright 1987 Annual Reviews. All rights reserved
Subject
Review Articles
ISSN
0066-4146
eISSN
1545-4282
DOI
10.1146/annurev.aa.25.090187.000553
Publisher site
See Article on Publisher Site

Abstract

Wolf-Rayet (W-R) stars are hot, luminous objects with strong, broad ( '" 103 km s -I ) emission lines in the optical region ( 189) due to a substantial stellar wind. The W-R phase is a normal stage of evolution for all stars initially more massive than ",40 M0' and these extreme Population I stars are the topic of this review. A W-R phase is also present in some central stars of planetary nebulae, which we do not discuss here. Some 160 indi­ vidual stars of this class are known in our own Galaxy, and many others have been identified among galaxies of the Local Group. W-R stars come in two major subtypes (22): the WN, in which lines of helium and nitrogen ions are seen; and the we, which contain lines of carbon and oxygen along with the helium ions. An additional minor subtype (WO) with strong 0 VI lines has also recently been identified ( 19). The main characteristic of the optical spectrum of W-R stars is the dominance of emission lines. In a few WN stars, hydrogen appears to be present (52, 159), but generally the spectra of W-R stars are notable for the absence

Journal

Annual Review of Astronomy and AstrophysicsAnnual Reviews

Published: Sep 1, 1987

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