Stars, Planets, and ISM Seminar

High Resolution Spectroscopy of RR Lyrae Stars

RR Lyraes are bright low-mass members of the HR Diagram helium core-burning horizontal branch.  Their mean absolute magnitudes are all about the same, M_V ~ +0.7, making them attractive targets in Cosmic Distance Ladder studies.  But they pulsate on average every half day, changing brightness, radius, spectral appearance by large amounts in the process.  This short-term variability has made progress slow on some aspects of RR Lyraes.  In this talk I'll describe recent progress on application of high resolution spectroscopy to large samples of RR Lyraes, which has solved many open questions about these multi-population highly evolved stars. Such work is increasing the usefulness of RR Lyraes for Galactic and near-field extragalactic evolutionary studies.