Evidence for Solar-like Oscillations in β Hydri

Abstract

We have made a clear detection of excess power, providing strong evidence for solar-like oscillations in the G2 subgiant ? Hyi. We observed this star over five nights with the University College London 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-1, and the mean noise level in the amplitude spectrum at frequencies above 0.5 mHz is 0.11 m s-1. We see a clear excess of power centered at 1.0 mHz, with peak amplitudes of about 0.5 m s-1, 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 ?Hz, also in good agreement with the known properties of ? Hyi.