CoRoT sounds the stars: p-mode parameters of Sun-like oscillations on HD 49933
Auvergne, M.; Baudin, F.; Jiménez-Reyes, S. J.; García, R. A.; Chaplin, W. J.; Michel, E.; Baglin, A.; Samadi, R.; Kjeldsen, H.; Mosser, B.; Barban, C.; Elsworth, Y.; Appourchaux, T.; Benomar, O.; Boumier, P.; Toutain, T.; Deheuvels, S.; Verner, G. A.; Hulot, J. -C.; Ballot, J.; Régulo, C.; Roxburgh, I. W.
France, United Kingdom, Germany, Spain, Denmark
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.