Towards an understanding of the Ofp phenomenon

We propose to observe the peculiar Of?p star HD191612 for 3*20 ks withXMMNewton. In the visible domain, this star displays spectacular line profilevariations alternating between two different spectral states (O6O8) with aperiod of virgul540d. A monitoring of this peculiar object in the Xray domain willprovide crucial information for constraining its nature. The requested XMM dataare part of a multiwavelength observing campaign that also includes coordinatedobservations in the UV (FUSE) and visible (groundbased telescopes) ranges. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]