SIMBAD references

Water vapor emission at 22GHz from masers associated with star-forming regions is highly variable. We present a database of up to 20 years of monitoring of a sample of 43 masers within star-forming regions. The sample covers a large range of luminosities of the associated IRAS source and is representative of the entire population of H₂O masers of this type. The database forms a good starting point for any further study of H₂O maser variability. The observations were obtained with the Medicina 32-m radiotelescope, at a rate of 4-5 observations per year. To provide a database that can be easily accessed through the web, we give for each source: plots of the calibrated spectra, the velocity-time-flux density plot, the light curve of the integrated flux, the lower and upper envelopes of the maser emission, the mean spectrum, and the rate of the maser occurrence as a function of velocity. Figures for just one source are given in the text for representative purposes. Figures for all the sources are given in electronic form the appendix. A discussion of the main properties of the H₂O variability in our sample will be presented in a forthcoming paper.