2011ApJ...731..123K

We present three transits of GJ 1214b, observed as part of the Apache Point Observatory Survey of Transit Light Curves of Exoplanets. By applying Markov Chain Monte Carlo techniques to a multi-wavelength data set which included our r-band light curves and previously gathered data of GJ 1214b, we confirm earlier estimates of system parameters. Using spectral energy distribution fitting, mass-luminosity relations, and light curve data, we derived absolute parameters for the star and planet, improving uncertainties by a factor of two for the stellar mass (M_{sstarf}= 0.153^+0.010_–0.009 M_☉), stellar radius (R_{sstarf}= 0.210^+0.005_–0.004R_☉), planetary radius (R_p= 2.74^+0.06_–0.05R_⊕), and planetary density (ρ_p= 1.68±0.23 g/cm3). Transit times derived from our study show no evidence for strong transit timing variations. We also report the detection of two features in our light curves which we believe are evidence for a low-energy stellar flare and a spot-crossing event.