a1 FNRS-ULg, Dept AGO, Allée du 6 Août 17, Bât B5C, B4000-Liège, Belgium, email: firstname.lastname@example.org
a2 Penn State Worthington Scranton, 120 Ridge View Drive, Dunmore, PA 18512, USA
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.