A quest for differential stellar rotation in A stars

Abstract

Photoelectric line-profile measurements of the Mg II line at 4481 A and the Fe II line at 4352 A in the A stars Alpha Aql, Alpha Peg, Beta Eri, Alpha Cep, Gamma Boo, and Gamma Her are subjected to Fourier analysis in order to detect differential rotation. Effects of limb darkening on a rotationally broadened line profile are considered and compared with those of differential rotation. In the analysis, a measured rotationally broadened flux profile is expressed as a convolution of the rotation profile, and the existence of differential rotation is identified by finding a line-profile transform having an anomalously small ratio of first to second sidelobe amplitudes. The results indicate that differential rotation is apparently absent in A stars