The combined effects of expansion and rotation on spectral line shapes

A convolving function for approximating the combined effects of stellar rotation and radial motion without a velocity gradient on spectral line shapes is developed. It is shown that the broadening function which is convolved with an intrinsic profile to write the observed profile is not simply related to the functions for pure rotation or pure radial motion. Thus if the line profile is asymmetric, the effects of rotation cannot be estimated by a convolution; mass-loss rates calculated by that method need to be revised.