A photometric investigation of RV Tauri and yellow semiregular variables.

Results are presented for DDO and UBV photoelectric photometry of 52 RV Tau and semiregular variables and candidates. CN abundances, effective temperatures, surface gravities, absolute visual magnitudes, and mass estimates are derived in the framework of the spectroscopic groupings proposed by Preston et al. (1963). The photometry suggests a further division of Preston's group A, and a possible physical connection is indicated between this group and the semiregular variables. The spectroscopic groups are shown to be well separated in the DDO color-color diagrams when mean colors are used for individual stars. An upper limit of about 3 solar masses is determined for stars in each group. A correlation between derived iron abundances and published IR excesses obtained from flux measurements at 3.6 and 11.3 microns is found which supports the contention that dust production in circumstellar shells increases with increasing metallicity.