A fresh look at the seismic spectrum of HD49933: analysis of 180 days of CoRoT photometry

TL;DR

This paper analyzes 180 days of CoRoT photometry of HD49933 to characterize its solar-like oscillations, identifying modes and measuring their properties despite challenges in estimating rotational splitting.

Contribution

It provides a robust analysis of HD49933's oscillation spectrum using multiple methods, improving mode identification and parameter estimation.

Findings

Consistent mode identification across methods

Precise measurements of mode frequencies, widths, and amplitudes

Large rotational splitting estimated at several microHz

Abstract

Solar-like oscillations have now been observed in several stars, thanks to ground-based spectroscopic observations and space-borne photometry. CoRoT, which has been in orbit since December 2006, has observed the star HD49933 twice. The oscillation spectrum of this star has proven difficult to interpret. Thanks to a new timeseries provided by CoRoT, we aim to provide a robust description of the oscillations in HD49933, i.e., to identify the degrees of the observed modes, and to measure mode frequencies, widths, amplitudes and the average rotational splitting. Several methods were used to model the Fourier spectrum: Maximum Likelihood Estimators and Bayesian analysis using Markov Chain Monte-Carlo techniques. The different methods yield consistent result, and allow us to make a robust identification of the modes and to extract precise mode parameters. Only the rotational splitting remains difficult to estimate precisely, but is clearly relatively large (several microHz in size).