New Initiatives on RR Lyrae Chemical Compositions

Chris Sneden
University of Texas

ABSTRACT

The discovery by Preston and colleagues of the neutron-capture-enhanced star TY Gru in the very metal-poor halo "HK survey" gradually awakened my interest in the chemical compositions of RR Lyrae stars. In this brief talk I discuss the main aspects of TY Gru and then spend the majority of time describing the PhD Thesis work of U. Texas graduate student BiQing For. This study considers in detail the cyclical changes in model atmosphere parameters and metallicities of 10 RRab stars, using spectroscopic data gathered in multiple observing runs with the duPont echelle at Las Campanas Observatory. Finally, I will briefly discuss the initial results in a new chemical composition study of RRc stars.