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Properties of the WO Wolf-Rayet stars

KINGSBURGH, RL; BARLOW, MJ; STOREY, PJ; (1995) Properties of the WO Wolf-Rayet stars. Astronomy & Astrophysics , 295 (1) pp. 75-100. Green open access

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Abstract

We present optical spectrophotometry for five WO Wolf-Rayet stars, three of them in our own Galaxy and one in each of the SMC and LMC. IUE ultraviolet spectrophotometry has also been obtained for the two Magellanic Cloud WO stars, including a high resolution spectrum for one of them. Quantitative spectral typing criteria are defined for WO subtypes spanning WO1 to WO5 and, for the case of the two WO stars in spectroscopic binaries, spectral types for the O-type primaries are derived. From our spectrophotometry we derive reddenings and magnitudes for each star. Absolute visual magnitudes of -2.5 and -1.8 are derived for a WO4 star and for a WO2 star, respectively, each star lying at a known distance. Wind terminal velocities ranging from 4200km/s to 5500km/s are derived from the black absorption edge of an ultraviolet P Cygni profile and from the FWZI of strong optical emission lines. The relative abundances of helium, carbon and oxygen in the winds of each of the WO stars are derived using a recombination theory analysis of selected ultraviolet and optical emission lines to determine the ionic abundances of He^2+^, C^4+^, O^4+^, O^5+^ and O^6+^. The derived abundance ratios show relatively narrow ranges. C/He number ratios of 0.51-0.52 are derived for two Galactic WO stars and one LMC WO star, with their C/O ratios ranging between 4.6 and 5.2, and their (C+O)/He ratios equal to 0.62. The one SMC WO star has a C/He ratio of 0.81, a C/O ratio of 2.7 and a (C+O)/He number ratio of 1.10. These abundance ratios are broadly consistent with evolutionary models for the advanced stages of massive stars, and promising agreement as a function of initial metallicity is found with the most recent evolutionary models.

Type: Article
Title: Properties of the WO Wolf-Rayet stars
Open access status: An open access version is available from UCL Discovery
Publisher version: https://ui.adsabs.harvard.edu/#abs/1995A&A...295.....
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Magellanic Clouds; Metallicity; Stellar Evolution; Stellar Mass Ejection; Wolf-Rayet Stars; Abundance; Emission Spectra; Iue; Line Spectra; Spectrum Analysis; Stellar Magnitude; Stellar Spectrophotometry; Ultraviolet Astronomy; Astronomy; STARS: WOLF-RAYET; STARS: MASS-LOSS; STARS: ABUNDANCES; STARS: EVOLUTION
UCL classification: UCL
UCL > Provost and Vice Provost Offices
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/10096153
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