CoRoT sounds the stars: p-mode parameters of Sun-like oscillations on HD 49933^*

¹ Institut d'Astrophysique Spatiale, UMR8617, Université Paris XI, Bâtiment 121, 91405 Orsay Cedex, France e-mail: Thierry.Appourchaux@ias.u-psud.fr
² LESIA, UMR8109, Université Pierre et Marie Curie, Université Denis Diderot, Observatoire de Paris, 92195 Meudon Cedex, France
³ School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
⁴ Astronomy Unit, Queen Mary, University of London Mile End Road, London E1 4NS, UK
⁵ Laboratoire AIM, CEA/DSM-CNRS - Univ. Paris 7 Diderot - IRFU/SAp, 91191 Gif-sur-Yvette Cedex, France
⁶ Max Planck Institut für Astrophysik, Karl-Schwarzschild-Str. 1, Postfach 1317, 85741 Garching, Germany
⁷ Instituto de Astrofísica de Canarias, 38205, La Laguna, Tenerife, Spain
⁸ Danish AsteroSeismology Centre (DASC), Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C, Denmark

Received: 30 May 2008
Accepted: 7 July 2008

Abstract

Context. The first asteroseismology results from CoRoT are presented, on a star showing Sun-like oscillations. We have analyzed a 60 day lightcurve of high-quality photometric data collected by CoRoT on the F5 V star HD 49933. The data reveal a rich spectrum of overtones of low-degree p modes.

Aims. Our aim was to extract robust estimates of the key parameters of the p modes observed in the power spectrum of the lightcurve.

Methods. Estimation of the mode parameters was performed using maximum likelihood estimation of the power spectrum. A global fitting strategy was adopted whereby 15 mode orders of the mode spectrum (45 modes) were fitted simultaneously.

Results. The parameter estimates that we list include mode frequencies, peak linewidths, mode amplitudes, and a mean rotational frequency splitting. We find that the average large frequency (overtone) spacing derived from the fitted mode frequencies is 85.9 ± 0.15 μHz. The frequency of maximum amplitude of the radial modes is at 1760 μHz, where the observed rms mode amplitude is 3.75 ± 0.23 ppm. The mean rotational splitting of the non-radial modes appears to be in the range ≈2.7 μHz to ≈3.4 μHz. The angle of inclination offered by the star, as determined by fits to the amplitude ratios of the modes, appears to be in the range ≈50 degrees to ≈62 degrees.