Transit mapping of a starspot on CoRoT-2
Probing a stellar surface with planetary transitsU. Wolter1, J. H. M. M. Schmitt1, K. F. Huber1, S. Czesla1, H. M. Müller1, E. W. Guenther 2, and A. P. Hatzes2
1 Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
2 Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
Received 14 April 2009 / Accepted 17 June 2009
We analyze variations in the transit lightcurves of CoRoT-2b, a massive hot Jupiter orbiting a highly active G star. We use one transit lightcurve to eclipse-map a photospheric spot occulted by the planet. In this case study we determine the size and longitude of the eclipsed portion of the starspot and systematically study the corresponding uncertainties. We determine a spot radius between and on the stellar surface and the spot longitude with a precision of about degree. Given the well-known transit geometry of the CoRoT-2 system, this implies a reliable detection of spots on latitudes typically covered by sunspots; the size of the modelled spot is comparable to large spot groups on the Sun. We discuss the future potential of eclipse mapping by planetary transits for the high-resolution analysis of stellar surface features.
Key words: stars: planetary systems -- stars: activity -- stars: late-type -- stars: imaging -- stars: individual: CoRoT-2
© ESO 2009