Be stars as rotating stars: observations

The classical rotational hypothesis for Be stars is reviewed and discussed. Methods of measuring rotational velocities are considered and the particular difficulties that Be stars pose in this respect are pointed out. Several tests of the rotational hypothesis are discussed and shown to support this idea. New observations of Balmer emission-line widths in the spectra of 46 Be stars show a correlation with rotational velocity, also in support of the rotational hypothesis. The very large emission widths found for some Be stars are discussed and possible reasons for the broadening are presented. (Auth.)