RR Lyrae Stars: Cosmic Lighthouses With a Twist
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138
Instituut voor Sterrenkunde, University of Leuven, Celestijnenlaan 200D, B 3001 Heverlee, Belgium
Invited review paper, received May 7, 2012
Since their discovery over a century ago, RR Lyrae stars have proven to be valuable objects for the entire field of astrophysics. They are used as standard candles and witnesses of galactic evolution. Though the pulsations that cause their light variations are dominated by relatively “simple” radial modes, some aspects of RR Lyrae pulsation remain enigmatic. Besides the visual, photographic, and photometric observations of these stars that span several decades, spectroscopic data provide an in-depth view on the pulsations. In the past decade, particularly since the launch of the satellite missions with asteroseismology as part of their program (for example, MOST, CoRoT, and Kepler), several findings have helped us better understand the structure and pulsations of RR Lyrae stars. Nevertheless, ground-based observations and long-term monitoring of RR Lyrae stars, as done by the AAVSO members, remain of utmost importance.