  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. To test these scenarios, we carried out a detailed
optical monitoring of HD45314, the hottest member of the class of gamma Cas
stars, along with dedicated X-ray observations on specific dates.
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. Over the last four
years, HD45314 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. The observed behaviour of
HD45314 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.
