EDP Sciences
The CoRoT space mission: early results
Free access
Volume 506, Number 1, October IV 2009
The CoRoT space mission: early results
Page(s) 263 - 268
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361/200911895
Published online 28 July 2009
A&A 506, 263-268 (2009)
DOI: 10.1051/0004-6361/200911895

On the differential rotation of CoRoT-2a

H.-E. Fröhlich1, M. Küker1, A. P. Hatzes2, and K. G. Strassmeier1

1  Astrophysikalisches Institut Potsdam (AIP), An der Sternwarte 16, 14482 Potsdam, Germany
    e-mail: HEFroehlich@aip.de
2  Thüringer Landessternwarte Tautenburg, Karl-Schwarzschild-Observatorium (TLS), Sternwarte 5, 07778 Tautenburg, Germany
    e-mail: artie@tls-tautenburg.de

Received 20 February 2009 / Accepted 15 July 2009

We apply a robust spot model to fit the light curve of CoRoT-2a. The spots are assumed to be long-living and each has its own rotation period. A model with three circular spots reproduces the basic features of the longitude-time spot coverage map. One of the spots exhibits a noticeably lower rotational frequency than the other two. From the rotational frequencies of the three dark features we infer a differential rotation of above 0.11 rad/d, in rough agreement with theoretical models. Mean field models of angular momentum transport by convection and meridional flow lead to an equatorial rotational frequency that exceeds that of the poles by 0.09 rad/d. The spot decay corresponds to a turbulent magnetic diffusivity of $(1.2\pm 0.1)\times 10^{13}$ cm2/s.

Key words: stars: activity -- stars: individual: CoRoT-2a -- stars: interiors -- stars: late-type -- stars: rotation -- starspots

© ESO 2009