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标题：Intriguing X-ray and optical variations of the γ Cassiopeiae analog HD 45314 ★
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作者：G. Rauw ; Y. Nazé ; M. A. Smith 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：615
DOI：10.1051/0004-6361/201731782
语种：English
出版社：EDP Sciences
摘要：Context.A growing number of Be and Oe stars, named theγCas stars, are known for their unusually hard and intense X-ray emission. This emission could either trace accretion by a compact companion or magnetic interaction between the star and its decretion disk.Aims.To test these scenarios, we carried out a detailed optical monitoring of HD 45314, the hottest member of the class ofγCas stars, along with dedicated X-ray observations on specific dates.Methods.High-resolution optical spectra were taken to monitor the emission lines formed in the disk, while X-ray spectroscopy was obtained at epochs when the optical spectrum of the Oe star was displaying peculiar properties.Results.Over the last four years, HD 45314 has entered a phase of spectacular variations. The optical emission lines have undergone important morphology and intensity changes including transitions between single- and multiple-peaked emission lines as well as shell events, and phases of (partial) disk dissipation. Photometric variations are found to be anti-correlated with the equivalent width of the Hαemission. Whilst the star preserved its hard and bright X-ray emission during the shell phase, the X-ray spectrum during the phase of (partial) disk dissipation was significantly softer and weaker.Conclusions.The observed behaviour of HD 45314 suggests a direct association between the level of X-ray emission and the amount of material simultaneously present in the Oe disk as expected in the magnetic star-disk interaction scenario.
关键词：Key wordsenstars: emission-line, Bestars: individual: HD 45314X-rays: stars