The Chemical Compositions of the SRd Variable Stars. I. XY Aquarii, RX Cephei, AB Leonis, and SV Ursae Majoris
Chemical compositions are derived from high-resolution spectra for four stars classed as SRd variables in the General Catalogue of Variable Stars. Two stars-XY Aquarii and RX Cephei-are of solar metallicity and most likely not variable stars. Their spectroscopic effective temperatures and surface gravities correspond to the spectral types G0 V for XY Aqr and G8 III for RX Cep. Two stars are undisputed variables and shown here to be metal-poor supergiants: AB Leonis with [Fe/H] ~=-1.6 and SV Ursae Majoris with [Fe/H] ~=-1.4. The metallicities and high radial velocities show them to be halo stars.