Nonradial p-modes in the G9.5 giant ϵ Ophiuchi? Pulsation model fits to MOST photometry^*

¹ Institute for Astronomy (IfA), University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria e-mail: kallinger@astro.univie.ac.at
² Institute for Computational Astrophysics, Department of Astronomy and Physics, Saint Marys University, Halifax, NS B3H 3C3, Canada
³ Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
⁴ Observatoire Astronomique du Mont Mégantic, Département de Physique, Université de Montréal, C. P. 6128, Succursale: Centre-Ville, Montréal, QC H3C 3J7 and Observatoire du mont Mégantic, Canada
⁵ Department of Astronomy and Astrophysics, David Dunlap Observatory, University of Toronto, PO Box 360, Richmond Hill, ON L4C 4Y6, Canada
⁶ Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA

Received: 27 June 2007
Accepted: 31 October 2007

Abstract

The G9.5 giant ϵ Oph shows evidence of radial p-mode pulsations in both radial velocity and luminosity. We re-examine the observed frequencies in the photometry and radial velocities and find a best model fit to 18 of the 21 most significant photometric frequencies. The observed frequencies are matched to both radial and nonradial modes in the best model fit. The small scatter of the frequencies about the model predicted frequencies indicate that the average lifetimes of the modes could be as long as 10–20 d. The best fit model itself, constrained only by the observed frequencies, lies within ± of ϵ Oph's position in the HR-diagram and the interferometrically determined radius.