Twenty-one new light curves of OGLE-TR-56b: New system parameters and limits on timing variations

Although OGLE-TR-56b was the second transiting exoplanet discovered, only one light curve, observed in 2006, has been published besides the discovery data. We present 21 light curves of 19 different transits observed between 2003 July and 2009 July with the Magellan Telescopes and Gemini South. The combined analysis of the new light curves confirms a slightly inflated planetary radius relative to model predictions, with R_p = 1.378 ± 0.090 R _J. However, the values found for the transit duration, semimajor axis, and inclination values differ significantly from the previous result, likely due to systematic errors. The new semimajor axis and inclination, a = 0.01942 ± 0.00015AU and i = 73°72± 0°18, are smaller than previously reported, while the total duration, T ₁₄ = 7931 ± 38s, is 18 minutes longer. The transit midtimes have errors from 23s to several minutes, and no evidence is seen for transit midtime or duration variations. Similarly, no change is seen in the orbital period, implying a nominal stellar tidal decay factor of Q _* = 10⁷, with a 3σ lower limit of 10^5.7.