2003A&A...402..653R

We report the analysis of the first high-resolution X-ray spectra of the Wolf-Rayet (WR) object WR25 (HD 93162, WN6ha+O4f) obtained with the reflection grating spectrometers (rgs) and the european photon imaging cameras (EPIC-MOS and PN) ccd spectrometers on board the XMM-Newton satellite. The spectrum exhibits bright emission lines of the H- and He-like ions of Ne, Mg, Si and S, as well as FeXVIII to FeXX and FeXXV lines. Line fluxes have been measured. The RGS and EPIC spectra have been simultaneously fitted to obtain self-consistent temperatures, emission measures, and elemental abundances. Strong absorption by the dense WR stellar wind and the interstellar medium (ISM) is observed equivalent to N_H=7x10²¹.cm^–2. Multi-temperature (dem) fitting yields two dominant components around temperatures of 7.0 and 32MK, respectively. The XMM intrinsic (i.e. unabsorbed, corrected for the stellar wind absorption and the absorption of ISM) X-ray luminosity of WR25 is L_x(0.5-10keV)=1.3x10³⁴erg/s, and L_x(0.5-10keV)=0.85x10³⁴erg/s, (when correcting for the ISM only) assuming d=3.24kpc. The obtained chemical abundances are subsolar, except for S. This may be real, but could equally well be due to a weak coupling to the continuum, which is strongly influenced by the absorption column density and the subtracted background. The expected high N-abundance, as observed in the optical wavelength region, could not be confirmed due to the strong wind absorption, blocking out its spectral signature. The presence of the FeXXV emission-line complex at ∼6.7keV is argued as being indicative for colliding winds inside a WR+O binary system.