Solar-like oscillations in red giants observed with Kepler: comparison of global oscillation parameters from different methods^⋆

¹ University of Birmingham, School of Physics and Astronomy, Edgbaston, Birmingham B15 2TT, UK
e-mail: saskia@bison.ph.bham.ac.uk
² Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
³ LESIA, UMR8109, Université Pierre et Marie Curie, Université Denis Diderot, Observatoire de Paris, 92195 Meudon Cedex, France
⁴ Laboratoire AIM, CEA/DSM-CNRS, Université Paris 7 Denis Diderot, IRFU/SAp, Centre de Saclay, 91191 Gif-sur-Yvette, France
⁵ Department of Physics and Astronomy, University of British Colombia, 6224 Agricultural Road, Vancouver, BC V6T 1Z1, Canada
⁶ Institute for Astronomy, University of Vienna, Türkenschanzstrasse 17, 1180 Vienna, Austria
⁷ High Altitude Observatory, NCAR, PO Box 3000, Boulder, CO 80307, USA
⁸ Sydney Institute for Astronomy (SIfA), School of Physics, University of Sydney, NSW 2006, Australia
⁹ Eureka Scientific, 2452 Delmer Street Suite 100, Oakland, CA 94602-3017, USA
¹⁰ Department of Mathematical Sciences, University of South Africa, Box 392, UNISA 0003, South Afrika
¹¹ Laboratoire d’Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 31400 Toulouse, France
¹² Universidad de La Laguna, Dpto de Astrofísica, 38206 Tenerife, Spain
¹³ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
¹⁴ NASA Ames Research Center, MS 244-30, Moffet Field, CA 94035, USA
¹⁵ SETI Institute, NASA Ames Research Center, MS 244-30, Moffet Field, CA 94035, USA
¹⁶ Orbital Sciences Corp., NASA Ames Research Center, Moffet Field, CA 94035, USA
¹⁷ Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
¹⁸ Department of Physics and Astronomy, Building 1520, Aarhus University, 8000 Aarhus C, Denmark

Received: 9 June 2010
Accepted: 13 August 2010

Abstract

Context. The large number of stars for which uninterrupted high-precision photometric timeseries data are being collected with Kepler and CoRoT initiated the development of automated methods to analyse the stochastically excited oscillations in main-sequence, subgiant and red-giant stars.

Aims. We investigate the differences in results for global oscillation parameters of G and K red-giant stars due to different methods and definitions. We also investigate uncertainties originating from the stochastic nature of the oscillations.

Methods. For this investigation we use Kepler data obtained during the first four months of operation. These data have been analysed by different groups using already published methods and the results are compared. We also performed simulations to investigate the uncertainty on the resulting parameters due to different realizations of the stochastic signal.

Results. We obtain results for the frequency of maximum oscillation power (ν_max) and the mean large separation (⟨ Δν ⟩) from different methods for over one thousand red-giant stars. The results for these parameters agree within a few percent and seem therefore robust to the different analysis methods and definitions used here. The uncertainties for ν_max and  ⟨ Δν ⟩  due to differences in realization noise are not negligible and should be taken into account when using these results for stellar modelling.

Conclusions.