A connection between macroturbulence and nonradial oscillations in late-type stars

The behavior of the mean amplitude of nonradial oscillations in late-type stellar atmospheres is considered. It is pointed out that the nonradial oscillation theory of Christy and Ando predicts larger velocity amplitudes in stars with high effective temperature and low log g. When comparing G dwarfs and K giants, the effective temperature and log g effects approximately cancel, but the lower gravities of K supergiants cause a large jump in nonradial amplitudes at bolometric magnitude of about -1. The resulting step-function dependence with luminosity closely resembles the very peculiar behavior of macroturbulence previously observed by Smith and Dominy. It is concluded that a large component of macroturbulence in the atmospheres of late-type stars is probably intimately tied to, if not directly caused by 5-minute-like nonradial oscillations.