Probing tiny convective cores with the acoustic modes of lowest degree

• Type: Article in International Scientific Journal
• Date: 2011

Authors

Cunha, MS (Author) FCUP; Brandao, IM (Author) Other

Journal

Title: Astronomy and Astrophysics

Vol. 529

Final page: A10

ISSN: 0004-6361

Publisher: EDP Sciences

Indexing

ISI Web of Knowledge - 16 Citations

Scopus - 16 Citations

Other information

Authenticus ID: P-002-S5J

DOI: 10.1051/0004-6361/201015188

Abstract (EN): Solar-like oscillations are expected to be excited in stars of up to about 1.6 solar masses. Most of these stars will have convective cores during their main-sequence evolution. At the edges of these convective cores, there is a rapid variation in the sound speed, which influences the frequencies of acoustic oscillations. In this paper we build on earlier work to investigate the impact that these rapid structural variations have on different p-mode frequency combinations, involving modes of low degree. In particular, we adopt a different expression to describe the sound speed variation at the edge of the core, which we show more closely reproduces the profiles derived from the equilibrium models. We analyse the impact of this change on the frequency perturbation derived for radial modes. Moreover, we consider three different small frequency separations involving modes of degree l = 0, 1, 2, 3, l = 0, 1, and l = 0, 2, and show that they are all significantly affected by the sharp sound speed variation at the edge of the core. In particular, we confirm that the frequency derivative of the diagnostic tool that combines modes of degree up to 3 can potentially be used to infer the amplitude of the relative sound speed variation directly at the edge of the core. We show that at high frequencies the other two diagnostic tools can be up to a few mu Hz smaller than what would be expected in the absence of the rapid structural variation at the edge of the core. Also, we show that the absolute values of their frequency derivatives are significantly increased, in a manner that strongly depends on stellar age.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 6