Wolf-Rayet wind structure and optical variability
Q. Li 1,5,
J.C. Brown 1,2,3,4,
R. Ignace * 1,
J.P. Cassinelli 1,4 and
L.M. Oskinova 1,6
Received 3 December 1999 / Accepted 8 March 2000
Results are presented on the expected variability of Wolf-Rayet (WR) stars in broad-band optical polarimetry and photometry, and in emission line profiles, due to an inhomogeneous random distribution of blobs in spherical geometry. Time dependent simulations are carried out with blob ejection random in time and direction, and the radiation properties are evaluated in the optically thin limit. In contrast with previous purely statistical analyses, inclusion in the present treatment of a velocity law and stellar occultation effects can yield results consistent with observations of the mean polarisation and the ratio of polarimetric to photometric variability. Such consistency puts constraints on model parameters. Indeed by considering combinations of the three observables , and it is possible to infer reasonably good estimates of three wind-blob parameters - the of their velocity law, the total mass loss rate in blobs and the total number of blobs emitted per wind flow time , provided the blobs are reasonably localised in angular and radial extent. It is found that typical data requires , and year. The estimate is consistent with the number of observed narrow features on emission lines. Smaller values of are excluded. This improved model shows that data do not after all demand very dense blobs as previously suggested, and offers a valuable diagnostic of WR wind structure parameters.
Key words: polarization stars: mass-loss stars: variables: general stars: Wolf-Rayet stars: winds, outflows
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© European Southern Observatory (ESO) 2000
Online publication: May 3, 2000