6.7 GHz light curve of S255IR-NIRS3 spanning ~27 yr. The integrated flux density from different observations is displayed in differently colored symbols depicted in the legend. The data from Goedhart et al. (2004) are represented by the average integrated flux density centered at the monitoring period of ~1450 days shown by the two horizontal magenta bars; the top and bottom bars correspond to the upper and lower values of the integrated flux density, respectively. The dashed violet line indicates the result of fitting three exponential functions to the data in different time intervals; the orange ellipses mark the starting points of each different fit interval. The inset panel shows the enlarged part of the light curve where an exponential rise starts.