the same color code as in Figure \[fig:get7phases\]. Measurements at each state are systematically offset from the mean flux during the orbit. Here, the correction lowers the RMS from 532 to 307 ppm.[]{data-label="fig:cor7phases"}](fig8.png){width="8cm"}

Monte-Carlo analysis {#sec:Monte Carlo analysis}
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The star and planet parameters are derived through a Markov Chain Monte-Carlo (MCMC) minimization process [@Burke2007]. We simultaneously fit the lightcurve with a transit model and an instrumental model. We adopt a quadratic limb-darkened transit model from @Mandel2002. The model parameters, some of which are degenerate, are the period $P$, the stellar mass $M_\star$, the stellar radius $R_\star$, the planet radius $R_p$, the inclination $i$, the mid-transit time for each visit $t_1$, $t_2$, $t_3$, and the limb-darkening coefficients $u_1$, $u_2$. For an efficient MCMC calculation, we remove degeneracy between parameters by using $R_\star$, $r=R_p/R_\star$, and the transit duration from first to fourth contact $\tau_{14}$, instead of $R_\star$, $R_p$, and $i$. For similar reasons, we use $a_1=u_1+2u_2$ and $a_2=2u_1-u_2$, instead of $u_1$ and $u_2$ (Holman et al. 2006). We fix $P$ and $M_\star$, the other parameters are free. We assume zero eccentricity, as indicated by radial velocity measurements [@Burke2007]. Initial values are taken from @Sing2011 and @Fernandez2009, except for the limb-darkening coefficients. 