EFFECT OF ELECTRON THERMAL MOTIONS ON THOMSON SCATTERED LINE-PROFILESFROM HOT CIRCUMSTELLAR ENVELOPES

The effect of electron thermal motions on the polarisation of light si ngle Thomson scattered in an optically thin circumstellar envelope is investigated. When the central star is a point source of continuum rad iation it is found that the scattered continuum polarisation is unaffe cted by the electron thermal motions and the familiar single scatterin g results dependent on envelope shape and stellar inclination are obta ined. However when the central star is a point source of line radiatio n the Doppler redistribution in frequency, due to the thermal motions of the isothermal envelope electrons, of scattered line radiation yiel ds a symmetrically broadened spectropolarimetric line profile (in the absence of envelope bulk motion). These effects are illustrated and di rectly compared with previous analysis of line polarisation arising th rough the Doppler redistribution of scattered radiation due to the bul k motions of the scattering material. It is shown that for early type stars, which possess slow (a few hundred km.s(-1)) winds, the ''therma l smearing'' effect cannot be ignored.