TY Gruis: A metal-poor carbon and neutron-capture-rich RR Lyrae star

We have conducted a photometric and high- resolution spectroscopic analysis of the high- latitude (l = 1 degrees, b = -55 degrees) metal- poor RR Lyrae star TY Gru (= CS 22881-071). We find this star to have large overabundances of carbon and neutron- capture elements. Mass transfer from an asymptotic giant branch binary companion prior to its RR Lyrae evolutionary state is the simplest explanation of this circumstance. Unfortunately, TY Gru is afflicted by the Blazhko effect, which greatly complicates accurate measurement of the motion of its center of mass. We have not yet detected the small orbital motion that would be produced by a distant degenerate companion of TY Gru.