The surprising X-ray emission of Oe stars

Oe stars are thought to represent an extension of the Be phenomenon to higher temperatures. Dedicated XMM observations of HD 155806 revealed a surprising X-ray spectrum: soft character, absence of overluminosity, broad X-ray lines. These properties are fully compatible with the wind-shock model, which usually explains the X-rays from ``normal', single O-type stars. In contrast, some other Oe/Be stars display a completely different behaviour at high energies.