Evidence for solar-like oscillations in beta Hydri

Abstract

We have made a clear detection of excess power, providing strong evidence for solar-like oscillations in the G2 subgiant beta Hyi. We observed this star over five nights with the UCLES echelle spectrograph on the 3.9-m Anglo-Australian Telescope, using an iodine absorption cell as a velocity reference. The time series of 1196 velocity measurements shows an rms scatter of 3.30 m/s, and the mean noise level in the amplitude spectrum at frequencies above 0.5 mHz is 0.11 m/s. We see a clear excess of power centred at 1.0 mHz, with peak amplitudes of about 0.5 m/s, in agreement with expectations for this star. Fitting the asymptotic relation to the power spectrum indicates the most likely value for the large separation is 56.2 microHz, also in good agreement with the known properties of beta Hyi.