Theoretical H-Beta Line Profiles and Related Parameters for Rotating B Stars

This paper presents a method for the calculation of Hp line profiles for rotating stars. Results are presented for a series of models spanning the B spectral class. In addition to the profiles, equivalent widths, photometric p-indices, and UB V colors are presented. Families of models are formed by using the results of recent studies of rotating stellar interiors, and variation of the line parameters due to effects of rotation are quantitatively calculated. Macroscopic effects on the star, such as shape distortion, aspect effects, gravity darkening, limb darkening, and latitude variation of atmospheric parameters, are included. Microscopic effects dealing with the line formation, such as pure absorption, non-coherent resonance scattering, and coherent electron scattering, are also included. It was found that the inclusion of resonance scattering as a source of opacity is important if accurate rotational profiles are to be obtained. Results are presented that demonstrate 50 per cent variation in Hp equivalent widths resulting from rotation for stars of the same (U - B)0. However, the effects of rotation on a color-color diagram are such as to move the model down the main sequence rather than away from it. An attempt is made to explain the observed correlation between variations in the photometric p-indices and V sin i. It is suggested that an increased number of observations of rotating B stars may enable one to determine the extent to which differential rotation is present in these stars.