Abundance analyses of field RV Tauri stars. V. DS Aquarii, UY Arae, TW camelopardalis, BT librae, U monocerotis, TT ophiuchi, R scuti, and RV Tauri

Abundance analyses are presented and discussed for eight RV Tauri variables . The RVB star UY Ara shows the abundance anomalies seen in other RVB stars , namely, elements that condense into grains at high temperature are undera bundant, but elements of low condensation temperature are much less underab undant. This pattern is ascribed to a separation of dust from gas with accr etion of gas but not dust by the atmosphere. Abundances for two RVC stars w ith earlier results for other RVC stars show that these intrinsically metal -poor stars do not show effects of dust-gas separation. Analyses of five RV A stars show that these cooler stars are very largely unaffected by dust-ga s separation. It is proposed that the deeper convective envelope of cooler stars dilutes anomalies resulting from dust-gas separation. Possible sites for dust formation and dust-gas separation-the dusty wind off the RV Tauri variable or a dusty circumbinary disk-are reviewed and observational tests suggested.