H₂O maser light curves of R Crt in 1987–2011, showing the integrated flux density, S, in different velocity intervals versus TJD (= Julian Date – 2440000.5). Spectra taken within three days were averaged before determining S. The vertical lines connect the first day of each of the years indicated at the top of the figure with the corresponding TJD on the lower axis. (a) S(tot) is the total flux of all maser emission, between 0 < V_los < 22 km s⁻¹. Observations marked with crosses are from Effelsberg, the dots mark data from Medicina. A phase of relatively weak maser activity in 5/1999–5/2002 is marked by a horizontal dotted line. (b− e) S is the integrated flux in the velocity intervals given in the individual panels.