FORS2 spectrophotometry and residuals obtained from using a single bin for each light curve subset, as described in Sect. 3.2.1. The three subsets of 5 December 2012 are shown in the left panel and correspond to wavelength ranges of (from top to bottom) 738−788, 788−898, and 898−1020 nm. The middle and right panels show the two subsets of 14 January 2013 and 7 February 2013, respectively, and correspond to wavelength ranges of (from top to bottom) 738−788, and 788−1020 nm. The models are shown as red solid lines and contain the parametrizations of external parameters as described in Table 2. The residuals are shown below the data which are partially offset for clarity.