Solar‐like Oscillations in the G2 Subgiant β Hydri from Dual‐Site Observations

Abstract

We have observed oscillations in the nearby G2 subgiant star beta Hyi using\nhigh-precision velocity observations obtained over more than a week with the\nHARPS and UCLES spectrographs. The oscillation frequencies show a regular comb\nstructure, as expected for solar-like oscillations, but with several l=1 modes\nbeing strongly affected by avoided crossings. The data, combined with those we\nobtained five years earlier, allow us to identify 28 oscillation modes. By\nscaling the large frequency separation from the Sun, we measure the mean\ndensity of beta Hyi to an accuracy of 0.6%. The amplitudes of the oscillations\nare about 2.5 times solar and the mode lifetime is 2.3 d. A detailed comparison\nof the mixed l=1 modes with theoretical models should allow a precise estimate\nof the age of the star.\n