Predicted and empirical radii of RR Lyrae stars

Abstract

We present new theoretical Period-Radius-Metallicity (PRZ) relations for RR Lyrae stars. Current predictions are based on a large set of nonlinear, convective models that cover a broad range of chemical abundances and input parameters. We also provide new and homogeneous estimates of angular diameters for a sample of field RR Lyrae stars using a recent calibration of the Barnes-Evans surface brightness relation. Predicted and empirical radii are, within the errors, in reasonable agreement, but in the short-period range the latter present a larger scatter. As a working hypothesis we suggest that this discrepancy might be due to the occurrence either of nonlinear features such as bumps or a steep rising branch. New distance determination for RR Lyr itself is in very good agreement with HST trigonometric parallax and with pulsation parallax.

arXiv comment12 pages, 3 figures, accepted on ApJ Letters

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• On the use of field RR Lyrae as Galactic probes: I. The Oosterhoff dichotomy based on fundamental variables
• A Preliminary Calibration of the RR Lyrae Period-Luminosity Relation at Mid-Infrared Wavelengths: WISE Data
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• A DECam View of the Diffuse Dwarf Galaxy Crater II: Variable Stars
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• Pulsation period variations in the RRc Lyrae star KIC 5520878
• CCD Photometry of the globular cluster M2. RR Lyrae physical parameters and new variables
• In search of RR Lyrae type stars in eclipsing binary systems. OGLE052218.07-692827.4: an optical blend
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• High-cadence stellar variability studies of RR Lyrae stars with DECam: New multi-band templates
• RRab variables with identical light-curve shapes at different pulsation periods