Decoding RR Lyrae light curves with deep learning for accurate absolute magnitude estimation

Public summary

* RR Lyrae stars are pulsating variable stars that serve as standard candles for measuring cosmic distances.

* A deep learning model trained on 80,000 RR Lyrae light curves predicts distances without metallicity.

* It achieves 1% distance precision for Milky Way mapping and independent Hubble-constant constraints.

Abstract

RR Lyrae stars are essential standard candles for distance measurements in the Milky Way and nearby galaxies. Traditional estimates rely on the period-absolute magnitude-metallicity relation but are limited by uncertainties in metallicity determinations. We present a deep learning approach that directly predicts absolute magnitudes from RRab and RRc light curves, eliminating the need for metallicity estimates. Our model achieves validation precisions of 0.053 and 0.036 mag (approximately 2.5% and 1.7% in distance) for individual RRab and RRc stars, respectively. Tests on globular clusters yield typical distance precisions of 1.0% for RRab and 1.7% for RRc stars. For the benchmark systems, combining the RRab- and RRc-based models yields distance moduli of 18.498 ± 0.001stat ± 0.018sys mag for the Large Magellanic Cloud and 19.564 ± 0.003stat ± 0.019sys mag for the Sculptor Dwarf Spheroidal Galaxy. These measurements are in excellent agreement with previous results, achieve a distance precision of approximately 1%, and represent a 1.8-fold improvement over traditional RR Lyrae calibration relations. Our approach showcases the ability of AI to directly extract key physical parameters from complex, information-rich light curves, resolve degeneracies, and scale to broader applications.