2006/05/24 by Fabio Bresolin, Grzegorz Pietrzyński, Grzegorz Pietrzynski +5 · 8 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Blue supergiant #Galaxy #Giant star #Luminosity #Red supergiant #Scientific Research and Discoveries #Spectral line #Stars #Stellar classification #Stellar, planetary, and galactic studies #Supergiant #astro-ph
paper · pdf · doi:10.1086/506200
published as Astrophys.J.648:1007-1019,2006 · Accepted for publication in the Astrophysical Journal. 14 pages, 10 figures
arxiv created 2006/05/24 · openalex publication_date 2006/09/08 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
As part of the Araucaria Project, we present the first spectral catalog of supergiant stars in the Local Group dwarf irregular galaxy WLM. In assigning a spectral classification to these stars we accounted for the low metal content of WLM relative to the galactic standards used in the MK process, by using classification criteria developed for B and A supergiants contained in the Small Magellanic Cloud. Our spectral catalog shows that our higher signal-to-noise ratio (S/N) spectroscopic sample of 19 objects contains at least six early B (B0-B5) supergiants and six late B and early A (B8-A2) stars of luminosity class between Ia and II, as well as an O7 V star and an O9.7 Ia star. The spectra of several of these stars are of sufficiently high quality for a determination of the stellar parameters and abundances. We have also acquired a second set of lower S/N spectra for mostly BA stars; however, their quality does not allow a further analysis. We have carried out a quantitative analysis for three early B supergiants. The mean oxygen abundance we derive is 12 + log(O/H) = 7.83 ± 0.12. This value agrees very well with the measurement that is obtained from H II regions. We therefore find no additional evidence for the discrepancy between stellar and nebular oxygen abundances measured for a single A-type supergiant by Venn et al. The analysis of B- and A-type supergiants yields compatible results for nitrogen, silicon, and magnesium. We show that the photometric variability of the blue supergiants included in our spectroscopic sample is negligible for the use of these stars as distance indicators.