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Centro de Astrofísica da Universidade do Porto

Solar-like oscillations in the G2 subgiant β Hydri from dual-site observations

T. R. Bedding, H. Kjeldsen, T. Arentoft, F. Bouchy, J. Brandbyge, B. J. Brewer, R. P. Butler, J. Christensen-Dalsgaard, T. Dall, S. Frandsen, C. Karoff, L. L. Kiss, M. J. P. F. G. Monteiro, F. P. Pijpers, T. C. Teixeira, C. G. Tinney, I. K. Baldry, F. Carrier, S. J. O'Toole

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

Keywords
stars: individual (β Hyi) — stars: oscillations

The Astrophysical Journal
Volume 663, Page 1315
July 2007

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