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标题：Wind and nebula of the M 33 variable GR 290 (WR/LBV) ⋆
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作者：Olga Maryeva ; Gloria Koenigsberger ; Oleg Egorov 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2018
卷号：617
DOI：10.1051/0004-6361/201732540
语种：English
出版社：EDP Sciences
摘要：Context.GR 290 (M 33/V532 = Romano’s Star) is a suspected post-luminous blue variable star located in M 33 galaxy that shows a rare Wolf–Rayet (WR) spectrum during its minimum light phase. In spite of many studies, its atmospheric structure, its circumstellar environment, and its place in the general context of massive stars’ evolution is poorly known.Aims.We present a detailed study of this star’s wind and mass loss, and a study of the circumstellar environment associated to the star.Methods.Long-slit spectra of GR 290 were obtained during its present minimum luminosity phase with the Gran Telescopio Canarias covering the ∼3600–7500 Å wavelength range together with contemporaneous photometry usingB,V,RandIfilters. The data were compared with non-local thermodynamical equilibrium (non-LTE) model atmosphere synthetic spectra computed with CMFGEN code and with models for ionized interstellar medium regions computed with CLOUDY code.Results.The currentmV= 18.8 mag is the faintest at which this source has ever been observed. The non-LTE models indicate effective temperatures ofTeff= 27 000–30 000 K at radiusR2/3= 27−21R⊙and mass-loss rateṀ= 1.5 × 10−5M⊙yr−1. The terminal wind speedv∞= 620 km s−1is faster than ever before recorded, while the current luminosityL*= (3.1–3.7) × 105L⊙is the lowest ever deduced. The star is overabundant in He and N and underabundant in C and O. It is surrounded by an unresolved compact H IIregion with dimensions ≤4 pc, from where H-Balmer, He Ilines, and [O III] and [N II] are detected. In addition, we find emission from a more extended interstellar medium (ISM) region, which appears to be asymmetric, with a larger extent to the east (16–40 pc) than to the west.Conclusions.In the present long lasting visual minimum, GR 290 is in a lower bolometric luminosity state with higher mass-loss rate. The nearby nebular emission seems to suggest that the star has undergone significant mass loss over the past 104–105yr and is nearing the end stages of its evolution.
关键词：enstars: Wolf–Rayetstars: variables: S Doradusstars: winds, outflowsstars: evolutionstars: individualGR 290galaxies: individual: M 33