Solar-like oscillations in β Hydri:: Confirmation of a stellar origin for the excess power

The G2 subgiant beta Hyi (HR 98) was observed with the CORALIE fiber-fed echelle spectrograph on the 1.2-m Swiss telescope at La Silla in June 2000. The resulting 971 high-accuracy radial velocities exhibit an rms scatter of 2.72 m s(-1) and a mean noise level in the amplitude spectrum of 0.122 m s(-1). These measurements show significant excess in the power spectrum between 0.7-1.4 mHz with 0.40 m s(-1) peak amplitude. Fitting the asymptotic relation to the power spectrum gives a large splitting of 58 mu Hz which is in good agreement with theoretical expectations. Our data confirm the independent detection of solar-like oscillations in beta Hyi announced by Bedding et al. (2001) which used the UCLES echelle spectrograph on the 3.9-m Anglo-Australian Telescope. Two independent instruments and calibration methods obtained very similar power excesses thus leaving little doubts on the stellar origin of the detected signal.