The MACHO Project LMC Variable Star Inventory. VII. The Discovery of RV Tauri Stars and New Type II Cepheids in the Large Magellanic Cloud

We report the discovery of RV Tauri stars in the Large Magellanic Cloud (LMC). In light- and color-curve behavior, the RV Tauri stars appear to be a direct extension of the type II Cepheids to longer periods. A single period-luminosity-color relationship is seen to describe both the type II Cepheids and the RV Tauri stars in the LMC. We derive the relation V_0 = 17.89(+/-0.20)-2.95(+/-0.12) log P + 5.49(+/-0.35)<(V - R)_0>, which is valid for type II Cepheids and RV Tauri stars in the period range 0.9 < log P < 1.75. Assuming a distance modulus to the LMC of 18.5, the relation in terms of the absolute luminosities becomes M_V = -0.61(+/-0.20)-2.95(+/-0.12) log P + 5.49(+/-0.35)<(V - R)_0>.