Analytic approximations for transit light curve observables and   uncertainties
  The light curve of an exoplanetary transit can be used to estimate the planetary radius and other parameters of interest. Because accurate parameter estimation is a non-analytic and computationally intensive problem, it is often useful to have analytic approximations for the parameters as well as their uncertainties and covariances. Here we give such formulas, for the case of an exoplanet transiting a star with a uniform brightness distribution. When limb darkening is significant, our parameter sets are still useful, although our analytic formulas underpredict the covariances and uncertainties. 
Joshua A. Carter, Jennifer C. Yee, Jason Eastman, B. Scott Gaudi,   Joshua N. Winn