To create the raw white light curve , we summed each spectrum over the 181 pixels in the spectral trace . The white light curve has systematic trends that are typical for WFC3 observations ( Zhou et al . 2017 ): the flux increases asymptotically over each orbit ( the " ramp " effect ) and there is a visit - long linear trend . The largest ramp occurs in the initial orbit ( orbit zero ) , so we only fit data from orbits one through four in our analysis , following common practice . We fit the light curve with the analytic model of the form F white ( t ) = S white ( t)×T white ( t ) , where S white is a systematics model and T white is a transit model . We used the same systematics model as Kreidberg et al . ( 2015 ) . We modelled the transit with the batman package ( Kreidberg 2015 ) . The model parameters are the orbital period p , time of inferior conjunction t 0 , transit depth r p /r s , ratio of semi - major axis to stellar radius a / r s , orbital inclination i , and the quadratic stellar limb darkening parameters u 1 and u 2 .