HD16691: an extreme O-type supergiant with magnetically confined windquestionMark

We propose to investigate the Xray properties of HD16691, an O4 supergiantbelieved to be a transition object between O and WolfRayet stars. Recentspectroscopic investigations by our team in the visible domain revealed astellar wind affected by a large scale corotating structure, perhaps related tothe interplay between the stellar magnetic field and the plasma outflow. Thisobject constitutes therefore a valuable target for investigating the role of thepotential magnetic confinement of the stellar wind. In addition, most of theOtype stars observed so far in Xrays belong to spectral types later than O5.An XMMNewton study of HD16691 will therefore contribute to complete the pictureof the Xray properties of earlytype stars. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]