Mode width fitting with a simple bayesian approach. Application to CoRoT targets HD 181420 and HD 49933

TL;DR

This paper introduces a Bayesian method for fitting stellar oscillation modes in CoRoT data, improving mode identification under low SNR conditions and demonstrating the impact of priors on fit quality.

Contribution

It presents a Bayesian approach with a continuous mode height profile to enhance mode fitting in low SNR asteroseismic data, addressing convergence issues and prior influence.

Findings

Bayesian fitting improves mode identification in noisy data.

Mode width increases with frequency in the studied stars.

Using priors carefully is crucial for reliable results.

Abstract

We investigate the asteroseismology of two solar-like targets as observed with the CoRoT satellite, with particular attention paid to the mode fitting. HD 181420 and HD 49933 are typical CoRoT solar-like targets (156 and 60-day runs). The low signal-to-noise ratio (SNR) of about 3-10 prevents us from unambiguously identifying the individual oscillation modes. In particular, convergence problems appear at the edges of the oscillation spectrum. HD 181420 and HD 49933 are typical CoRoT solar-like targets (156 and 60-day runs). The low signal-to-noise ratio (SNR) of about 3-10 prevents us from unambiguously identifying the individual oscillation modes. In particular, convergence problems appear at the edges of the oscillation spectrum. We apply a Bayesian approach to the analysis of these data. We compare the global fitting of the power spectra of this time series, obtained by the classical maximum likelihood (MLE) and the maximum a posteriori (MAP) estimators. We examine the impact of the choice of the priors upon the fitted parameters. We also propose to reduce the number of free parameters in the fitting, by replacing the individual estimate of mode height associated with each overtone by a continuous function of frequency (Gaussian profile). The MAP appears as a powerful tool to constrain the global fits, but it must be used carefully and only with reliable priors. The mode width of the stars increases with the frequency over all the oscillation spectrum.