Abstract

We present accurate V-band photometry for a planetary transit of OGLE-TR-111 acquired with VIMOS at the ESO Very Large Telescope. The measurement of this transit allows us to refine the planetary radius, obtaining R p = 1.01 ± 0.06 RJ. Given the mass of Mp = 0.53 MJ previously measured from radial velocities, we confirm that the density is ρp = 0.6 ± 0.2 g cm-3. We also revise the ephemeris for OGLE-TR-111-b, obtaining an accurate orbital period P = 4.014484 ± 0.000014 days and predicting that the next observable transits would occur around December 2006, and after that only in mid-2008. Even though this period is different from previously published values, we cannot yet rule out a constant period. © 2007. The American Astronomical Society. All rights reserved.