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WR 7a: a V Sagittae or a qWR star?
Article first published online: 2 DEC 2003
DOI: 10.1111/j.1365-2966.2003.07157.x
Issue
Monthly Notices of the Royal Astronomical Society
Volume 346, Issue 3, pages 963–967, December 2003
Additional Information
How to Cite
Oliveira, A. S., Steiner, J. E. and Cieslinski, D. (2003), WR 7a: a V Sagittae or a qWR star?. Monthly Notices of the Royal Astronomical Society, 346: 963–967. doi: 10.1111/j.1365-2966.2003.07157.x
Publication History
- Issue published online: 2 DEC 2003
- Article first published online: 2 DEC 2003
- Accepted 2003 August 26. Received 2003 June 11
- Abstract
- Article
- References
- Cited By
Keywords:
- stars: emission-line, Be;
- stars: fundamental parameters;
- stars: individual: WR 7a;
- stars: Wolf–Rayet
ABSTRACT
The star WR 7a, also known as SPH 2, has a spectrum that resembles that of V Sagittae stars although no O vi emission has been reported. The Temporal Variance Spectrum – TVS – analysis of our data shows weak but strongly variable emission of O vi lines which is below the noise level in the intensity spectrum.
Contrary to what is seen in V Sagittae stars, optical photometric monitoring shows very little, if any, flickering. We found evidence of periodic variability. The most likely photometric period is Pphot= 0.227(±14) d, while radial velocities suggest a period of Pspec= 0.204(±13) d. One-day aliases of these periods can not be ruled out. We call attention to similarities with HD 45166 and DI Cru (= WR 46), where multiple periods are present. They may be associated to the binary motion or to non-radial oscillations.
In contrast to a previous conclusion by Pereira et al., we show that WR 7a contains hydrogen. The spectrum of the primary star seems to be detectable as the N v 4604 Å absorption line is visible. If so, it means that the wind is optically thin in the continuum and that it is likely to be a helium main sequence star.
Given the similarity to HD 45166, we suggests that WR 7a may be a qWR – quasi Wolf–Rayet – star. Its classification is WN4h/CE in the Smith, Shara & Moffat three-dimensional classification system.