Abstract

As part of our ongoing effort to measure exoplanet sizes and transit times with greater accuracy, we present I-band observations of two transits of OGLE-TR-111b. The photometry has an accuracy of 0.15%-0.20% and a cadence of 1-2 minutes. We derive a planetary radius of R-P = 1.067 +/- 0: 054R(Jup) and a stellar radius of R-S = 0.831 +/- 0.031 R-circle dot. The uncertainties are dominated by errors in the photometry rather than by systematic errors arising from uncertainties in the limb-darkening function or the stellar mass. Both the stellar radius and the planetary radius are in agreement with theoretical expectations. The transit times are accurate to within 30 s and allow us to refine the estimate of the mean orbital period: 4.0144479 +/- 0.0000041 days.