The first X-ray survey of Galactic luminous blue variables⋆
GAPHE, Département AGO, Université de Liège,
Allée du 6 Août 17, Bât. B5C, 4000 -
Received: 7 September 2011
Accepted: 23 November 2011
Aims. The X-ray emission of massive stars has been studied when these objects are in their main-sequence phase, as well as when they are in their Wolf-Rayet phase. However, the X-ray properties of the transitional luminous blue variable (LBV) phase remain unknown.
Methods. Using a dedicated but limited XMM-Newton survey and archival XMM-Newton and Chandra observations, we performed the first X-ray survey of LBVs: about half of the known LBVs or candidate LBVs were studied.
Results. Apart from the well known X-ray sources eta Car and Cyg OB2 #12, four additional LBVs are detected in this survey, though some doubt remains on the association with the X-ray source for two of these. For the other LBVs, upper limits on the flux were derived, down to log [LX/LBOL] − 9.4 for P Cyg. This variety in the strength of the X-ray emission is discussed, with particular emphasis on the potential influence of binarity.
Key words: X-rays: stars / stars : mass-loss / stars: early-type / stars: variables: S Doradus
© ESO, 2012