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

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© 2007. The American Astronomical Society. All rights reserved. Printed in U.S.A.
, , Citation Timothy R. Bedding et al 2007 ApJ 663 1315 DOI 10.1086/518593

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Author affiliations

1 School of Physics A28, University of Sydney, NSW 2006, Australia

2 Danish AsteroSeismology Centre (DASC), Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark

3 Observatoire de Genève, Ch. des Maillettes 51, CH-1290 Sauverny, Switzerland

4 Laboratoire d'Astrophysique de Marseille, Traverse du Siphon, BP 8, 13376 Marseille Cedex 12, France

5 Carnegie Institution of Washington, Department of Terrestrial Magnetism, 5241 Broad Branch Road NW, Washington, DC 20015-1305

6 European Southern Observatory, Casilla 19001, Santiago 19, Chile

7 Faculdade de Ciências and Centro deCentro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal

8 Blackett Laboratory, Imperial College London, South Kensington, London SW7 2BW, UK

9 Anglo-Australian Observatory, P.O. Box 296, Epping, NSW 1710, Australia

10 Astrophysics Research Institute, Liverpool John Moores University, Egerton Wharf, Birkenhead, CH41 1LD, UK

11 Instituut voor Sterrenkunde, Katholieke Universiteit Leuven, Celestijnenlaan 200 B, 3001 Leuven, Belgium

Dates

  1. Received 2006 December 20
  2. Accepted 2007 March 28
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0004-637X/663/2/1315

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. These 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 days. A detailed comparison of the mixed l = 1 modes with theoretical models should allow a precise estimate of the age of the star.

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10.1086/518593