Astronomy and Astrophysics, volume 615A, 44-44 (2018/7-1)
Intriguing X-ray and optical variations of the γ Cassiopeiae analog HD 45314.
RAUW G., NAZE Y., SMITH M.A., MIROSHNICHENKO A.S., GUARRO FLO J., CAMPOS F., PRENDERGAST P., DANFORD S., GONZALEZ-PEREZ J.N., HEMPELMANN A., MITTAG M., SCHMITT J.H.M.M., SCHRODER K.-P. and ZHARIKOV S.V.
Abstract (from CDS):
Context. A growing number of Be and Oe stars, named the γ 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 γ 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 Hα 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.
© ESO 2018
stars: emission-line, Be - stars: individual: HD 45314 - X-rays: stars
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