APOSTLE Observations of GJ 1214b: System Parameters and Evidence for Stellar Activity

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 _sun), stellar radius (R _sstarf = 0.210^+0.005 _-0.004 R _sun), planetary radius (R_p = 2.74^+0.06 _-0.05 R _⊕), and planetary density (ρ _p = 1.68 ± 0.23 g cm^-3). 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.