Julian date. The priors for the parameters are similar to those defined in [@Burke2007; @Burke2010]: equivalent to uniform on $R_\star$, $R_p$ , and $i$ for $R_\star$, $r$, and $\tau$, and uniform for the other parameters. A correction for the 7 readout states is applied during the process, using the known detector state at each image as calculated section \[sec:Extraction of instrumental parameters\]. The flux offset generated by each state is calculated using the whole visit. The likelihood is modeled as independent Gaussian residuals with uncertainty adjusted from two trial runs to enforce a final reduced $\chi^2$ of 1. The value $\sigma= 380$ ppm is adopted, and remains fixed during the MCMC run. This uncertainty is treated as white noise. We adopt the median as the best estimate of the posterior probability, and the 1$\sigma$ uncertainties of the parameter estimates are determined such that they demarcate 68.3% of the MCMC samples. The first 1000 iterations are discarded as burn-in period of the MCMC procedure.

Our choice of the parameters for the instrumental model is guided by the data. In many trial parameter sets, we examine sets including $F_0$, $x$, $y$, $\alpha$, $w$, $T$, the HST orbital phase $\phi$, and quadratic and 