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

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

Abstract

We present XMM-Newton observations of the B giant β 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  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.