Discovery of solar-like oscillations in the red giant<i>ε</i> Ophiuchi

Abstract

We present the discovery of solar-like oscillations in time-series of the G9.5 red giant ε Ophiuchi. The data were obtained with the CORALIE spectrograph at the 1.2 m Swiss telescope in La Silla and the ELODIE spectrograph at the 1.93 m telescope at the Observatoire de Haute Provence. Periodic variations can be observed in the radial velocity time series of individual nights. In the power spectrum of the radial velocity time series there is a clear power excess around 60 μHz, and several individual oscillation frequencies can be distinguished. Our auto-correlation and comb response analysis reveals a large separation of either 4.8 μHz or (its 11.57 μHz alias) 6.7 μHz. We estimate the position of ε Oph in the HR diagram, and verify whether CESAM shell hydrogen-burning stellar models exist that can reproduce the observed frequency separation.