Phased V -band light curve of IK Tau in 2002–2016. Red points are the observations from the AAVSO International Database and the black curve is the smoothed light curve with a Savitzky-Golay filter. The phases of relevant NH₃ observationsare labelled by vertical lines and on the top axis, with the same colour scheme as Fig. C.1. The label “VLA” represents the 2004 VLA observation. The numerals after “D”, “C”, and “B” are the ordinal numbers representingthe dates of VLA observations in 2015–2016 with the corresponding arrays (“B4” is discarded, see Tables A.1 and A.2).