Measuring stellar oscillations using equivalent widths of absorption lines

Kjeldsen et al. have developed a new technique for measuring stellar oscillations, and claimed a detection in the G subgiant eta Boo. The technique involves monitoring temperature fluctuations in a star via their effect on the equivalent width of Balmer lines. In this paper we use synthetic stellar spectra to investigate the temperature dependence of the Balmer lines, Ca II, Fe I, the Mg b feature and the G band. We present a list of target stars likely to show solar-like oscillations, and estimate their expected amplitudes. We also show that centre-to-limb variations in Balmer-line profiles allow one to detect oscillation modes with l less than or equal to 4, which accounts for the detection by Kjeldsen et al. of modes with degree l=3 in integrated sunlight.