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Paper: Using RR Lyrae Stars as High-Precision Distance Indicators in the Infrared
Volume: 514, Stellar Populations and the Distance Scale
Page: 129
Authors: Neeley, J. R.; Marengo, M.; Bono, G.; Braga, V. F.; Marconi, M.; Dall'Ora, M.; Magurno, D.
Abstract: RR Lyrae stars have the potential to be high-precision distance indicators, and serve as the anchor for a distance ladder composed of Population II stars. Theoretical pulsation models predict a significant contribution of metallicity on the zero point of the period–luminosity relations (Leavitt laws). Given the range of [Fe/H] values that these stars exhibit, any calibrations of the Leavitt law for RR Lyrae stars must include metallicity information. Empirically, we have characterized the Leavitt law at mid-infrared wavelengths in five Galactic globular clusters, which were observed withthe Spitzer Space Telescope as part of the Carnegie RR Lyrae Program. At this time we do not have the necessary statistics to empirically measure the metallicity component. For now, we provide a preliminary calibration of the Leavitt law at the 3.6 and 4.5 μm bands, using the average slope obtained from these five clusters combined with a zero point derived from five Galactic RR Lyrae stars with known parallax measurements.
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