Context : As a planet eclipses its parent star , a dark spot on the surface of the star may be occulted , causing a detectable variation in the light curve .

Aims : Study these light curve variations during transits and infer the physical characteristics of the stellar spots .

Methods : A total of 77 consecutive transit light curves of CoRoT-2 were observed with a high temporal resolution of 32 s , corresponding to an uninterrupted period of 134 days .
By analyzing small intensity variations in the transit light curves , it was possible to detect and characterize spots at fixed positions ( latitude and longitude ) on the surface of the star .
The model used simulates planetary transits and enables the inclusion of spots on the stellar surface with different sizes , intensities ( i.e . temperatures ) , and positions .
Fitting the data by this model , it is possible to infer the spots physical characteristics .
Because what is observed is the stellar flux blocked by the spots , there is a degeneracy between the spots intensity and area .
Thus the fits were either in spot longitude and radius , with a fixed intensity , or in spots longitude and intensity , for spots of constant size .
The model allowed up to 9 spots to be present at the stellar surface within the transit band .

Results : Before the modeling of the spots were performed , the planetary radius relative to the star radius was estimated by fitting the deepest transit to minimize the effect of spots .
A slightly larger ( 3 % ) radius , 0.172 R _ { star } , resulted instead of the previously reported 0.1667 R _ { star } .
The fitting of the transits yield spots , or spot groups , with sizes of ranging from 0.2 to 0.7 planet radius , R _ { p } , with a mean of 0.41 \pm 0.13 R _ { p } ( \sim 100,000 km ) , resulting in a stellar area covered by spots within the transit latitudes of 10-20 % .
The intensity varied from 0.4 to 0.9 of the disk center intensity , I _ { c } , with a mean of 0.60 \pm 0.19 I _ { c } , which can be converted to temperature by assuming blackbody emission for both the photosphere and the spots .
Considering an effective temperature of 5625 K for the stellar photosphere , the spots temperature ranges mainly from 3600 to 5000 K .

Conclusions : The spot model used here was able to estimate the physical characteristics of the spots on CoRoT-2 , such as size and intensity .
These results are in agreement with those found for magnetic activity analysis from out of transit data of the same star .