Letter to the Editor

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

¹ Institut d'Astrophysique Spatiale, CNRS, Université Paris XI, 91405 Orsay, France e-mail: othman.benomar@ias.u-psud.fr
² Danish AsteroSeismology Centre (DASC), Department of Physics and Astronomy, University of Aarhus, 8000 Aarhus C, Denmark
³ Centro de Astrofísica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal
⁴ School of Physics and Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
⁵ Laboratoire AIM, CEA/DSM-CNRS, Université Paris Diderot, IRFU/SAp, Centre de Saclay, 91191 Gif-sur-Yvette, France
⁶ Center for Information Technology, University of Oslo, PO Box 1059 Blindern, 0316 Oslo, Norway
⁷ Astronomy Unit, Queen Mary, University of London Mile End Road, London E1 4NS, UK
⁸ Laboratoire d'Astrophysique de Toulouse-Tarbes, Université de Toulouse, CNRS, 31400 Toulouse, France
⁹ LESIA, UMR8109, Université Pierre et Marie Curie, Université Denis Diderot, Observatoire de Paris, 92195 Meudon, France
¹⁰ Indian Institute of Astrophysics, Koramangala, Bangalore 560034, India
¹¹ Instituto de Astrofísica de Canarias, 38205 La Laguna, Tenerife, Spain
¹² Universidad de La Laguna, Dpto de Astrofísica, 38206 La Laguna, Tenerife, Spain

Received: 12 August 2009
Accepted: 15 October 2009

Abstract

Context. 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.

Aims. 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.

Methods. Several methods were used to model the Fourier spectrum: Maximum Likelihood Estimators and Bayesian analysis using Markov Chain Monte-Carlo techniques.

Results. 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 μHz in size).