EDP Sciences
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Volume 437, Number 2, July II 2005
Page(s) 599 - 609
Section Stellar structure and evolution
DOI http://dx.doi.org/10.1051/0004-6361:20052650

A&A 437, 599-609 (2005)
DOI: 10.1051/0004-6361:20052650

XMM-Newton observations of $\beta$ Centauri (B1 III): The temperature structure in the hot plasma and the photosphere-wind connection

A. J. J. Raassen1, 2, J. P. Cassinelli3, N. A. Miller4, R. Mewe1 and E. Tepedelenlioglu5

1  SRON National Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
    e-mail: a.j.j.raassen@sron.nl
2  Astronomical Institute "Anton Pannekoek", Kruislaan 403, 1098 SJ Amsterdam, The Netherlands
3  Dept. of Astronomy, University of Wisconsin at Madison, 6251 Sterling Hall, North Charter Str., Madison, WI 53706, USA
4  Dept. of Physics & Astronomy, University of Wisconsin-Eau Claire, 105 Garfield Avenue, Eau Claire WI 54702, USA
5  Physics Deparment, University of Wisconsin-Madison, 1150 University Ave., Madison, WI 53706, USA

(Received 6 January 2005 / Accepted 16 March 2005)

We present XMM-Newton observations of the B giant $\beta$ Centauri (B1 III). The spectra are rich of spectral lines from a wide range of ionization stages which indicate temperatures in the range ~0.1-0.6 keV. Simultaneous fits to the RGS, EPIC-MOS, and EPIC-pn spectra yield three plasma temperatures (0.1, 0.2, and 0.6 keV), emission measures, and elemental abundances which are quite close to solar values. These temperatures are confirmed by DEM modeling. According to the derived models the intrinsic source X-ray luminosity in the energy range 0.3-10 keV is $L_{\rm
x} = 10 \times 10^{30}$ erg s-1 at a distance of 161 pc. An analysis of the X-ray light curve suggests that the photospheric variability does not have much of an effect on the properties of the X-ray luminosity. The sensitivity of the He-like forbidden and intercombination lines to a strong ultraviolet stellar radiation field is used to constrain the radial distances at which the lines of Ne IX, O VII, and N VI originate.

Key words: stars: early-type -- stars: winds, outflows -- stars: variables: $\beta$ Cephei

SIMBAD Objects

© ESO 2005