Millimagnitude optical photometry for the transiting extrasolar planetary candidate OGLE-TR-171

RODRIGO F. DÍAZ; JOSÉ MIGUEL FERNÁNDEZ; SEBASTIÁN RAMÍREZ; DANTE MINNITI; PABLO J. D. MAUAS

Santiago, Chile

Workshop; Observing Planetary System - An ESO Workshop; 2007

We obtained high-quality optical (V) images with VIMO S at the ESO VLT, in order to get a very precise light curve of the transit of OGLE-TR-171. The resulting light curve has an rmsof about 5.6 mmag, comparable to photon noise . We refine the ephemeris for this transit and measure accurately the eclipse depth , which agrees with the amplitude provided byOGLE. The transit presents a marked V-shape, which together with its large amplitude indicates that the system is a grazing eclipsing stellar binary. This is confirmed measuring anellipsoidal variability with an amplitude of 1.2 mmag in the OGLE data.