About the p-mode frequency shifts in HD 49933

¹ Instituto de Astrofísica de Canarias, 38200, La Laguna, Tenerife, Spain
e-mail: salabert@oca.eu
² Departamento de Astrofísica, Universidad de La Laguna, 38206, La Laguna, Tenerife, Spain
³ Université de Nice Sophia-Antipolis, CNRS, Observatoire de la Côte d’Azur, BP 4229, 06304 Nice Cedex 4, France
⁴ Institut de Recherche en Astrophysique et Planétologie, CNRS, 14 Av. E. Belin, 31400 Toulouse, France
⁵ Université de Toulouse, UPS-OMP, IRAP, 31400 Toulouse, France
⁶ Laboratoire AIM, CEA/DSM-CNRS, Université Paris 7 Diderot, IRFU/SAp, Centre de Saclay, 91191 Gif-sur-Yvette, France
⁷ High Altitude Observatory, NCAR, PO Box 3000, Boulder, CO 80307, USA

Received: 2 February 2011
Accepted: 27 April 2011

Abstract

We study the frequency dependence of the frequency shifts of the low-degree p modes measured in the F5V star HD 49933, by analyzing the second run of observations collected by the CoRoT satellite. The 137-day light curve is divided into two subseries corresponding to periods of low and high stellar activity. The activity-frequency relationship is obtained independently from the analysis of the mode frequencies extracted by both a local and a global peak-fitting analyses, and from a cross-correlation technique in the frequency range between 1450 μHz and 2500 μHz. The three methods return consistent results. We show that the frequency shifts measured in HD 49933 present a frequency dependence with a clear increase with frequency, reaching a maximal shift of about 2 μHz around 2100 μHz. Similar variations are obtained between the l = 0 and l = 1 modes. At higher frequencies, the frequency shifts show indications of a downturn followed by an upturn, consistent between the l = 0 and 1 modes. We show that the frequency variation of the p-mode frequency shifts of the solar-like oscillating star HD 49933 has a comparable shape to the one observed in the Sun, which is understood to arise from changes in the outer layers due to its magnetic activity.