Volume 503, Number 2, August IV 2009
|Page(s)||521 - 531|
|Section||Stellar structure and evolution|
|Published online||02 July 2009|
Asteroseismology and interferometry of the red giant star ϵ Ophiuchi
Instituut voor Sterrenkunde, Katholieke Universiteit, 200D Celestijnenlaan, 3001 Leuven, Belgium e-mail: firstname.lastname@example.org
2 Astronomy Department, Yale University, PO Box 208101, New Haven CT 06520-8101, USA
3 Homi Bhabha Centre for Science Education, TIFR, V. N. Purav Marg, Mankhurd, Mumbai 400088, India
4 European Southern Observatory, Alonso de Córdova 3107, Casilla 19001, Santiago 19, Chile
5 Center for High Angular Resolution Astronomy, Georgia State University, PO Box 3965, Atlanta, Georgia 30302-3965, USA
6 LESIA, Observatoire de Paris, CNRS UMR 8109, UPMC, Université Paris Diderot, 5 Place Jules Janssen, 92195 Meudon, France
7 Institut d'Astrophysique Spatiale, CNRS/Université Paris XI UMR 8617, 91405 Orsay Cedex, France
8 GRAAL, Université Montpellier II, CNRS UMR 5024, 34095 Montpellier Cedex 05, France
9 Institut für Astronomie, Universität Wien, Türkenschanzstrasse 17, 1180 Vienna, Austria
10 Department of Physics & Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver V6T 1Z1, Canada
11 National Optical Astronomy Observatories, 950 North Cherry Avenue, Tucson, AZ 85719, USA
Accepted: 10 June 2009
The GIII red giant star ϵ Oph has been found to exhibit several modes of oscillation by the MOST mission. We interpret the observed frequencies of oscillation in terms of theoretical radial p-mode frequencies of stellar models. Evolutionary models of this star, in both shell H-burning and core He-burning phases of evolution, are constructed using as constraints a combination of measurements from classical ground-based observations (for luminosity, temperature, and chemical composition) and seismic observations from MOST. Radial frequencies of models in either evolutionary phase can reproduce the observed frequency spectrum of ϵ Oph almost equally well. The best-fit models indicate a mass in the range of 1.85 ± 0.05 with radius of 10.55 ± 0.15. We also obtain an independent estimate of the radius of ϵ Oph with highly accurate interferometric observations in the infrared K' band, using the CHARA/FLUOR instrument. The measured limb-darkened disk angular diameter of ϵ Oph is 2.961 ± 0.007 mas. Together with the Hipparcos parallax, this translates into a photospheric radius of R = 10.39 ± 0.07 . The radius obtained from the asteroseismic analysis matches the interferometric value quite closely even though the radius was not constrained during the modelling.
Key words: stars: individual: ϵ Ophiuchi / stars: oscillations / stars: interiors / stars: fundamental parameters / techniques: interferometric
© ESO, 2009
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