Amplitudes and lifetimes of solar-like oscillations observed by CoRoT^⋆

Red-giant versus main-sequence stars

¹ Institut d’Astrophysique Spatiale, CNRS, Université Paris XI, 91405 Orsay Cedex, France
e-mail: frederic.baudin@ias.u-psud.fr
² LESIA, Université Pierre et Marie Curie, Université Denis Diderot, Obs. de Paris, 92195 Meudon Cedex, France
³ Institut d’Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août 17, 4000 Liège, Belgium
⁴ Instituut voor Sterrenkunde, K.U. Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium
⁵ School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
⁶ Astronomical Institute “Anton Pannekoek”, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
⁷ Institut de Recherche en Astrophysique et Planétologie, CNRS, Université de Toulouse, 31400 Toulouse, France
⁸ Thüringer Landessternwarte, 07778 Tautenburg, Germany
⁹ University of Vienna, Institute for Astronomy, Türkenschanzstrasse 17, 1180 Vienna, Austria
¹⁰ Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Road, BC V6T 1Z1 Vancouver, Canada

Received: 11 January 2010
Accepted: 8 February 2011

Abstract

Context. The advent of space-borne missions such as CoRoT or Kepler providing photometric data has brought new possibilities for asteroseismology across the H-R diagram. Solar-like oscillations are now observed in many stars, including red giants and main-sequence stars.

Aims. Based on several hundred identified pulsating red giants, we aim to characterize their oscillation amplitudes and widths. These observables are compared with those of main-sequence stars in order to test trends and scaling laws for these parameters for main-sequence stars and red giants.

Methods. An automated fitting procedure is used to analyze several hundred Fourier spectra. For each star, a modeled spectrum is fitted to the observed oscillation spectrum, and mode parameters are derived.

Results. Amplitudes and widths of red-giant solar-like oscillations are estimated for several hundred modes of oscillation. Amplitudes are relatively high (several hundred ppm) and widths relatively small (very few tenths of a μHz).

Conclusions. Widths measured in main-sequence stars show a different variation with the effective temperature from red giants. A single scaling law is derived for mode amplitudes of red giants and main-sequence stars versus their luminosity to mass ratio. However, our results suggest that two regimes may also be compatible with the observations.