Seismic detection of acoustic sharp features in the CoRoT target HD 49933

¹ Homi Bhabha Centre for Science Education, TIFR, V. N. Purav Marg, Mankhurd, Mumbai 400088, India
e-mail: anwesh@tifr.res.in
² LESIA, Observatoire de Paris, UMR8109 CNRS, Université Pierre et Marie Curie, Université Denis Diderot, Place J. Janssen, 92195 Meudon, France
³ Tata Institute of Fundamental Research, Homi Bhabha Road, Mumbai 400005, India
⁴ Astronomy Department, Yale University, PO Box 208101, New Haven, CT 065208101, USA

Received: 22 November 2011
Accepted: 10 February 2012

Abstract

The technique of determining the acoustic location of layers of sharp changes in the sound speed inside a star from the oscillatory signal in its frequencies is applied to a solar-type star, the CoRoT target, HD 49933. We are able to determine the acoustic depth of the second helium ionisation zone of HD 49933 to be 794_-68⁺⁵⁵ s. The acoustic depth of the base of the convective zone is found to be 1855_-412⁺¹⁷³ s where the large error bars reflect the ambiguity in the result, which is difficult to determine with present precision on the frequencies because of the intrinsically weak nature of the signal. The positions of both these layers are consistent with those in a representative stellar model of HD 49933.