SIMBAD references

We present the first period-luminosity and period-radius relation of Galactic RV Tauri variable stars. We have surveyed the literature for all variable stars belonging to this class and compiled the full set of their photometric and spectroscopic measurements. We crossmatched the final list of stars with the Gaia Data Release 2 database and took the parallaxes, G-band magnitudes, and effective temperatures to calculate the distances, luminosities, and radii using a probabilistic approach. As it turned out, the sample was very contaminated, and thus we restricted our study to those objects for which the RV Tau nature was securely confirmed. We found that several stars are located outside the red edge of the classical instability strip, which implies a wider pulsational region for RV Tau stars. The period-luminosity relation of galactic RV Tauri stars is steeper than that of the shorter-period Type II Cepheids, in agreement with previous results obtained for the Magellanic Clouds and globular clusters. The median masses of RVa and RVb stars were calculated to be 0.45-0.52 M_☉ and 0.83 M_☉, respectively.