TY  - JOUR
A1  - Oskinova, Lida
A1  - Feldmeier, Achim
A1  - Hamann, Wolf-Rainer
T1  - High-resolution X-ray spectroscopy of bright O-type stars
JF  - Monthly notices of the Royal Astronomical Society
N2  - Archival X-ray spectra of the four prominent single, non-magnetic O stars zeta Pup, zeta Ori, xi Per and zeta Oph, obtained in high resolution with Chandra HETGS/MEG have been studied. The resolved X-ray emission line profiles provide information about the shocked, hot gas which emits the X-radiation, and about the bulk of comparably cool stellar wind material which partly absorbs this radiation. In this paper, we synthesize X-ray line profiles with a model of a clumpy stellar wind. We find that the geometrical shape of the wind inhomogeneities is important: better agreement with the observations can be achieved with radially compressed clumps than with spherical clumps. The parameters of the model, i.e. chemical abundances, stellar radius, mass-loss rate and terminal wind velocity, are taken from existing analyses of UV and optical spectra of the programme stars. On this basis, we also calculate the continuum-absorption coefficient of the cool-wind material, using the Potsdam Wolf-Rayet (POWR) model atmosphere code. The radial location of X-ray emitting gas is restricted from analysing the FIR line ratios of helium-like ions. The only remaining free parameter of our model is the typical distance between the clumps; here, we assume that at any point in the wind there is one clump passing by per one dynamical time-scale of the wind. The total emission in a model line is scaled to the observation. There is a good agreement between synthetic and observed line profiles. We conclude that the X-ray emission line profiles in O stars can be explained by hot plasma embedded in a cool wind which is highly clumped in the form of radially compressed shell fragments.
KW  - stars : individual : zeta Pup
KW  - stars : individual : zeta Ori
KW  - stars : individual : xi Per
KW  - stars : individual : zeta Oph
KW  - X-rays : stars
Y1  - 2006
U6  - https://doi.org/10.1111/j.1365-2966.2006.10858.x
SN  - 0035-8711
VL  - 372
SP  - 313
EP  - 326
PB  - Oxford University Press
CY  - Oxford
ER  -