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Issue A&A
Volume 504, Number 2, September III 2009
Page(s) 561 - 564
Section Stellar atmospheres
DOI http://dx.doi.org/10.1051/0004-6361/200912329
Published online 15 July 2009

A&A 504, 561-564 (2009)
DOI: 10.1051/0004-6361/200912329

Transit mapping of a starspot on CoRoT-2

Probing a stellar surface with planetary transits
U. 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
    e-mail: [uwolter;jschmitt]@hs.uni-hamburg.de
2  Thüringer Landessternwarte Tautenburg, Sternwarte 5, 07778 Tautenburg, Germany
    e-mail: [guenther;artie]@tls-tautenburg.de

Received 14 April 2009 / Accepted 17 June 2009

Abstract
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 $4.5\degr$ and $10.5\degr$ on the stellar surface and the spot longitude with a precision of about $\pm 1$ 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

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