Flux density vs. line-of-sight velocity V_los as a function of time (FVt-plot) for water-masers in R Cas. Each horizontal dotted line indicates an observation (spectra taken within 4 days from each other were averaged). The data were resampled to a resolution of 0.3 km s⁻¹ and only emission at levels ≥3σ is shown. The black area in the plot indicates the unobserved parts of the spectrum on these particular days. The first spectrum in this plot was taken on 10 September 1987; JD = 2447048.5, TJD = JD-2440000.5 = 7048. The last spectrum in the panel is from 21 December 2023.