Preprint Logo P96 October
2004


To be published in:
Astronomy & Astrophysics

An XMM-Newton look at the Wolf-Rayet star WR 40 +
The star itself, its nebula and its neighbours

E. Gosset*, Y. Nazé**, J.-F. Claeskens, G. Rauw*, J.-M. Vreux and H. Sana**


Institut d'Astrophysique et de Géophysique - Université de Liège, Allée du 6 Août, Bât B5c, B-4000 Liège (Sart Tilman), Belgium

* Research Associate FNRS, Belgium
** Research Fellow FNRS, Belgium

+ Based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).


Abstract

     We present the results of an XMM-Newton observation of the field of the Wolf-Rayet star WR 40. Despite a nominal exposure of 20 ks and the high sensitivity of the satellite, the star itself is not detected: we thus derive an upper limit on its X-ray flux and luminosity. Joining this result to recent reports of a non-detection of some WC stars, we suggest that the X-ray emission from single normal Wolf-Rayet star could often be insignificant despite remarkable instabilities in the wind. On the basis of a simple modelling of the opacity of the Wolf-Rayet wind of WR 40, we show that any X-ray emission generated in the particular zone where the shocks are supposed to be numerous will indeed have little chance to emerge from the dense wind of the Wolf-Rayet star. We also report the non-detection of the ejecta nebula RCW 58 surrounding WR 40. Concerning the field around these objects, we detected 33 X-ray sources, most of them being previously unknown: we establish a catalog of these sources and cross-correlate it with catalogs of optical/infrared sources.

Key Words
stars:individual: WR 40 -- stars: early-type -- stars: Wolf-Rayet -- X-rays: stars -- ISM:individual: RCW 58 -- ISM: bubbles

Files
Article: xmmwr40.pdf (1496516 bytes): HTTP FTP (ftp://vela.astro.ulg.ac.be/preprints/)


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