Towards an understanding of the Of?p star HD191612: phase-resolved multiwavelength observations
Walborn, Nolan R.; Nazé, Yaël; Howarth, Ian D.; Pollock, A. M. T.; Rauw, Gregor
Belgium, Spain, United States, United Kingdom
Abstract
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 LX/LBOL) 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' (0.2-0.6keV) 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 (absorption/emission) 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.
Based on observations collected at the Haute-Provence Observatory (France) and with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA). E-mail: naze@astro.ulg.ac.be ‡ Post-doctoral Researcher FNRS (Belgium). § Research Associate FNRS (Belgium). ¶ Operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555.