The effect of gravity darkening on spectral lines in a rotating star

Abstract

For rapidly rotating stars, the effect of gravity darkening on the equivalent width (EW) of spectral lines is very small, even when the rotation velocity is close to the critical velocity. But the effect on the full-width at half-maximum (FWHM) is relatively strong. At ω ≈ 0.99, the variation is 8%. For main-sequence stars in the range of spectral type B0 to B9, the variation of FWHM is almost independent of the spectral type when the rotation is small ( ω < 0.8); for rapidly rotators ( ω ≈ 0.99), the percentage variation of FWHM decreases with advancing spectral subclass.