Towards an understanding of the Of?p star HD191612: Phase-resolved multiwavelength observations

Yael Naze(1), Gregor Rauw (1), A.M.T. Pollock (2), Nolan R. Walborn (3), Ian D. Howarth (4)

1=ULg Belgium; 2=ESA; 3=STScI; 4=UCL, UK

We present the analysis of phase-resolved X-ray and optical observations of the peculiar hot star HD191612 (Of?p). This star is known to display line-profile variations that are recurrent with a period of 538d and its spectrum was found to present the signature of a magnetic field. In the X-rays, it is slightly overluminous compared to the canonical L_X/L_BOL relation and appears brighter when the optical lines are strongest. Our XMM-Newton observations further reveal that the X-ray spectrum of HD191612 exhibits rather broad lines and is dominated by a `cool' (0.2-0.6 keV) thermal component, two characteristics at odds with the proposed magnetic rotator model. We also report for the first time the low-level variability of the metallic (abs/em) lines and HeII absorptions that appear to be associated with radial-velocity shifts. Finally, we compare our results with observations of the early-type stars and discuss several possible scenarios.

Reference: MNRAS, in press
Status: Manuscript has been accepted


Comments: 10p, 10 fig