Measurements of spectral line asymmetries for Arcturus and the sun

Spectral line asymmetries have been measured in photospheric lines of Arcturus and the sun. The asymmetries are not detectable in weak lines but increase with line strength to 3% of the continuum for Arcturus and 5% of the continuum for the sun. The direction of the asymmetry for Arcturus is opposite that for the sun, with the line cores shifted toward shorter wavelengths for Arcturus and longer wavelengths for the sun. Possible explanations of the asymmetries include granulation motions and acoustic waves.