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

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 L_x = 10 × 10³⁰ 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.