Spectral line detrending model for the 2021 March 24 dataset. A clear trend is visible between the stellar line contrast and the S/N at 550 nm. To characterize this relationship, we fit the out-of-transit data (filled disks) with a second-order polynomial (solid grey line). Using this best-fit model we perform a "vertical stretching" to the time series spectra to detrend the data accordingly.