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WR 7a: a V Sagittae or a qWR star? | | Alexandre S. Oliveira
; J. E. Steiner
; D. Cieslinski
; | | Date: |
2 Sep 2003 | | Journal: | Mon.Not.Roy.Astron.Soc. 346 (2003) 963 | | Subject: | astro-ph | | Affiliation: | IAG-USP, Brazil), J. E. Steiner (IAG-USP, Brazil) and D. Cieslinski (INPE, Brazil | | 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 P(phot) = 0.227(14) d, while radial velocities suggest a period of P(spec) = 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. (1998), we show that WR 7a contains hydrogen. The spectrum of the primary star seems to be detectable as the N V 4604A 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 et al. (1996) three dimensional classification system. | | Source: | arXiv, astro-ph/0309043 | | Services: | Forum | Review | PDF | Favorites | |
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