Asteroseismology from multi-month Kepler photometry: the evolved Sun-like stars KIC 10273246 and KIC 10920273

¹ Centro de Astrofísica, DFA-Faculdade de Ciências, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
e-mail: campante@astro.up.pt
² Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C, Denmark
e-mail: campante@phys.au.dk
³ High Altitude Observatory, National Center for Atmospheric Research, Boulder, Colorado 80307, USA
⁴ Institut d’Astrophysique Spatiale, Université Paris XI – CNRS (UMR8617), Bâtiment 121, 91405 Orsay Cedex, France
⁵ Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006, Australia
⁶ School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
⁷ Laboratoire AIM, CEA/DSM-CNRS-Université Paris Diderot, IRFU/SAp, Centre de Saclay, 91191 Gif-sur-Yvette, France
⁸ LESIA, CNRS, Université Pierre et Marie Curie, Université Paris Diderot, Observatoire de Paris, 92195 Meudon Cedex, France
⁹ INAF Osservatorio Astrofisico di Catania, via S. Sofia 78, 95123 Catania, Italy
¹⁰ Materials Engineering Research Institute, Faculty of Arts, Computing, Engineering and Sciences, Sheffield Hallam University, Sheffield S1 1WB, UK
¹¹ Astronomical Institute Anton Pannekoek, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
¹² Departamento de Astrofísica, Universidad de La Laguna, 38206 La Laguna, Tenerife, Spain
¹³ Instituto de Astrofísica de Canarias, 38200 La Laguna, Tenerife, Spain
¹⁴ Astronomy Unit, Queen Mary, University of London, Mile End Road, London E1 4NS, UK
¹⁵ Australian Astronomical Observatory, PO Box 296, Epping NSW 1710, Australia
¹⁶ Institute of Astronomy, University of Vienna, 1180 Vienna, Austria
¹⁷ Astronomical Institute, University of Wrocław, ul. Kopernika 11, 51-622 Wrocław, Poland
¹⁸ SETI Institute/NASA Ames Research Center, Moffett Field, CA 94035, USA
¹⁹ Orbital Sciences Corporation/NASA Ames Research Center, Moffett Field, CA 94035, USA

Received: 1 February 2011
Accepted: 16 August 2011

Abstract

Context. The evolved main-sequence Sun-like stars KIC 10273246 (F-type) and KIC 10920273 (G-type) were observed with the NASA Kepler satellite for approximately ten months with a duty cycle in excess of 90%. Such continuous and long observations are unprecedented for solar-type stars other than the Sun.

Aims. We aimed mainly at extracting estimates of p-mode frequencies – as well as of other individual mode parameters – from the power spectra of the light curves of both stars, thus providing scope for a full seismic characterization.

Methods. The light curves were corrected for instrumental effects in a manner independent of the Kepler science pipeline. Estimation of individual mode parameters was based both on the maximization of the likelihood of a model describing the power spectrum and on a classic prewhitening method. Finally, we employed a procedure for selecting frequency lists to be used in stellar modeling.

Results. A total of 30 and 21 modes of degree l = 0,1,2 – spanning at least eight radial orders – have been identified for KIC 10273246 and KIC 10920273, respectively. Two avoided crossings (l = 1 ridge) have been identified for KIC 10273246, whereas one avoided crossing plus another likely one have been identified for KIC 10920273. Good agreement is found between observed and predicted mode amplitudes for the F-type star KIC 10273246, based on a revised scaling relation. Estimates are given of the rotational periods, the parameters describing stellar granulation and the global asteroseismic parameters Δν and ν_max.