The nature of p-modes and granulation in HD 49933

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  • 28 November 2008
Abstract
Context. Oscillations on the Procyon-like star HD 49933 (F5V) were obtained recently by CoRoT. A full reduction and analysis of the data by the CoRoT team yielded a detailed spectrum of l = 0, 1, and 2 p-modes. Aims. To provide our own independent reductions and stellar modeling of the CoRoT oscillation data for HD 49933. Methods. We used a new Bayesian Markov Chain Monte Carlo method to fit Lorentzian mode profiles to the observed power density spectrum to obtain a list of frequencies. We then searched several dense and extensive grids of stellar model oscillation spectra for models whose oscillation spectra best matches the derived frequencies. We quantified the statistical probability of the best model fits using a Bayesian approach. Results. We identify 24 frequencies. In contrast to the original CoRoT analysis we find no statistically significant evidence for l = 2 (or 3) modes. Our best fit model has solar composition and lies within the error box of the observationally derived HR-diagram location for HD 49933. We also show that lower Z models have a lower probability of matching the observations and we discuss new spectroscopic evidence for a solar metallicity of HD 49933.

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