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Paper: Progress on Infrared Period-Luminosity Relations for RR Lyrae Stars
Volume: 529, RR Lyrae/Cepheid 2019: Frontiers of Classical Pulsators
Page: 249
Authors: Neeley, J. R.; Marengo, M.; Sarajedini, A.; Freedman, W. L.; Madore, B. F.; Beaton, R. L.; Braga, V. F.
Abstract: RR Lyrae period-luminosity relations have long been an important tool in the nearby Universe, but in recent years they have earned greater attention as constructing a Population II distance ladder that is independent of Classical Cepheids has become more critical to the measurement of the Hubble Constant. Most of this work in this area has focused on the infrared, where the relations are tighter and steeper. Furthermore, the usefulness of period-luminosity and period-Wesenheit relations extends beyond measuring distances, since they can also be used to measure the metallicity distribution and differential reddening of the old stellar population of galaxies and clusters. Here, I will summarize recent progress on infrared period-luminosity relations, with calibrations coming from Gaia DR2 parallaxes of Galactic field stars. The effect of metallicity can now be measured empirically, and it is consistent with theoretical predictions. At present, the precision of the period-luminosity relations as distance indicators is still limited by the uncertainties in parallaxes of the calibration sample.
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