A comprehensive look at RR Lyrae stars through high-precision photometry and astrometry
Abstract
The TESS and Gaia missions are both collecting data of exquisite quality for RR Lyrae-type pulsating stars. We combine light curve shape information from TESS with distances and brightnesses from Gaia to build a detailed classification scheme that is able to filter out intrinsically fainter binaries and rotational variables as well as short-period Cepheids that otherwise have light curves very similar to that of RR Lyrae stars, while preserving targets with unusual light curve shapes. We build a clean sample from the RR Lyrae stars in the vicinity of the Sun, out to 5-10 kpc distances. Based on the TESS light curves we find that a large fraction of RR Lyrae stars exhibit various additional low-amplitude modes. The distribution of extra modes in period is markedly different from that of stars within the bulge and globular clusters, signaling a metallicity dependence in the mode periods and excitation mechanisms. We also detect a possible dependence of extra modes from color and hence effective temperatures in overtone RRc stars. While these new results have brought us closer to true asteroseismic analysis of RR Lyrae stars, we show through new échelle-type diagrams that mode identification is still hindered by the strong influence of the radial mode(s) dominating the pulsation.