XMM-Newton X-ray study of early type stars in the Carina OB1 association ^*,**

¹ Sternberg Astronomical Institute, Moscow University, Universitetskij Prospect 13, Moscow 119992, Russia e-mail: igor@sai.msu.ru
² Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 août, 17 Bât. B5c, 4000 Liège, Belgium
³ Department of Physics and Astronomy, University of Glasgow, Kelvin Building, Glasgow G12 8QQ, Scotland, UK
⁴ SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
⁵ Astronomical Institute Anton Pannekoek, University of Amsterdam, Kruislaan 403, 1098 SJ Amsterdam, The Netherlands

Received: 29 May 2006
Accepted: 10 October 2007

Abstract

Aims.X-ray properties of the stellar population in the Carina OB1 association are examined with special emphasis on early-type stars. Their spectral characteristics provide some clues to understanding the nature of X-ray formation mechanisms in the winds of single and binary early-type stars.

Methods.A timing and spectral analysis of five observations with XMM-Newton is performed using various statistical tests and thermal spectral models.

Results.235 point sources have been detected within the field of view. Several of these sources are probably pre-main sequence stars with characteristic short-term variability. Seven sources are possible background AGNs. Spectral analysis of twenty four sources of type OB and WR 25 was performed. We derived spectral parameters of the sources and their fluxes in three energy bands. Estimating the interstellar absorption for every source and the distance to the nebula, we derived X-ray luminosities of these stars and compared them to their bolometric luminosities. We discuss possible reasons for the fact that, on average, the observed X-ray properties of binary and single early type stars are not very different, and give several possible explanations.