Period-Color and Amplitude-Color Relations at Maximum and Minimum Light for RR Lyrae Stars in the SDSS Stripe 82 Region

Abstract

Investigation of period-color (PC) and amplitude-color (AC) relations at the maximum and minimum light can be used to probe the interaction of the hydrogen ionization front (HIF) with photosphere and the radiation hydrodynamics of the outer envelopes of Cepheids and RR Lyraes. For example, theoretical calculations indicated that such interactions would occur at minimum light for RR Lyrae and result in a flatter PC relation. In the past, the PC and AC relations have been investigated by using either the $(V-R{)}_{MACHO}$ or $(V-I)$ colors. In this work, we extend previous work to other bands by analyzing the RR Lyraes in the Sloan Digital Sky Survey Stripe 82 Region. Multi-epoch data is available for RR Lyraes located within the footprint of the Stripe 82 Region in five ($ugriz$) bands. We present the PC and AC relations at maximum and minimum light in four colors: $(u-g{)}_0$, $(g-r{)}_0$, $(r-i{)}_0$ and $(i-z{)}_0$, after they are corrected for extinction. We found that the PC and AC relations for this sample of RR Lyraes show a complex nature in the form of flat, linear or quadratic relations. Furthermore, the PC relations at minimum light for fundamental mode RR Lyrae stars are separated according to the Oosterhoff type, especially in the $(g-r{)}_0$ and $(r-i{)}_0$ colors. If only considering the results from linear regressions, our results are quantitatively consistent with the theory of HIF-photosphere interaction for both fundamental and first overtone RR Lyraes.

12 pages, 3 Tables, 9 Figures. ApJ accepted

References in corpus (3)

• The Period-Luminosity Relation of RR Lyrae Stars in the SDSS Photometric System
• On the Variation of Fourier Parameters for Galactic and LMC Cepheids at Optical, Near-Infrared and Mid-Infrared Wavelengths
• Empirical Period-Color and Amplitude-Color Relations for Classical Cepheids and RR Lyrae Variables

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• The stellar photosphere-hydrogen ionization front interaction in Classical Pulsators: a theoretical explanation for observed period-colour relations
• Period-Colour and Amplitude-Colour relations for OGLE-$\delta$ Scuti stars in the Galactic Bulge and LMC
• High-cadence stellar variability studies of RR Lyrae stars with DECam: New multi-band templates
• Reconsidering The Bailey Diagrams of ab-type RR Lyrae Stars, Metallicity-Mediated Evolution as the Direct Cause of the Oosterhoff Phenomenon