期刊
ASTRONOMY & ASTROPHYSICS
卷 615, 期 -, 页码 -出版社
EDP SCIENCES S A
DOI: 10.1051/0004-6361/201731782
关键词
stars: emission-line, Be; stars: individual: HD45314; X-rays: stars
资金
- ARC grant for Concerted Research Actions - French Community of Belgium (Wallonia-Brussels Federation), from the Fonds de la Recherche Scientifique (FRS/FNRS)
- XMM PRODEX contract (Belspo)
- universitiy of Hamburg
- university of Guanajuato
- university of Liege
- DGAPA/PAPIIT Project [IN100617]
Context. A growing number of Be and Oe stars, named the gamma Cas 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 of gamma Cas 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 H alpha emission. 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.
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