X-ray temperatures and their radial distributions from winds of O-type supergiants: the effects of clumps

¹ National Astronomical Observatories/Yunnan Observatory, Chinese Academy of Science, PR China e-mail: guojh@ynao.ac.cn
² Key Laboratory for the Structure and Evolution of Celestial Objects, Chinese Academy of Sciences, PR China

Received: 13 July 2009
Accepted: 15 December 2009

Abstract

Context. Based on the multiphase hydrodynamical flows and the clump model, a two-fluid model of the O stars ζ Ori A and ζ Pup is investigated, in which the flow is described by a set of two components.

Aims. I investigate the influence of clumps on the production of X-ray and derive wind parameters from a comparison with the X-ray temperature distributions in the wind of O-type supergiants.

Methods. The velocity structure of the clump is assumed to be beta law, thus the transonic velocity structure of the ambient wind can be attained via the shooting method.

Results. The mass, filling factor, and velocity structure of the clump are very sensitive to the post-shock temperatures. I find that the filling factor must be about 0.01 for fitting the observed X-ray temperatures. The mass of the clump cannot be smaller than 10¹⁸ g. A clump carries about 10^-4 and 10^-5 for ζ Ori A and ζ Pup, respectively. The model with the exponent of clump velocity β = 0.5-0.6 for O-type supergiants fits the observations better than one with the exponent β = 0.8.

Conclusions. These results indicate that the forward shock scenario can explain the X-ray emission, except for the hottest X-ray lines for O-type supergiants. Theoretical and observable evidence shows that a low velocity law should be applied to O-type supergiants.