RV Tauri stars
RV Tauri stars(tor -ÿ, -ee) A small group of very luminous pulsating variables, typified by RV Tauri, R Scuti, and R Sagittae, that are principally G and K stars with some F stars. They are yellow supergiants with extended atmospheres of gas that emit infrared radiation and have possibly been driven off by the pulsations. They have very characteristic light curves with alternating deep and shallow minima and periods ranging from 20 to 145 days. Because the luminosity fluctuations can be disturbed quite significantly in shape, period, etc., being most pronounced for longer-period stars, they are classified as semiregular variables. RV Tauri stars can be distinguished from other similar yellow semiregular stars by the variation in their color index, which mimics the light curve but goes through its maximum a little before the luminosity minimum. A small group have double periodicity; DF Cygni has two separate luminosity oscillations, a rapid 50 day oscillation being superimposed on a much slower 780 day oscillation with a much greater amplitude.
RV Tauri stars[¦är¦vē ′tȯr·ē ‚stärz]
A class of stars; they are long-period pulsating variable types with periods from about 50 to 150 days; otherwise they are like the shorter-period W Virginis stars; they are found in both the Milky Way Galaxy and the globular clusters.