Near-infrared Mira Period–Luminosity Relations in M33

Abstract

We analyze sparsely sampled near-infrared ( JHK s ) light curves of a sample of 1781 Mira variable candidates in M33, originally discovered using I -band time-series observations. We extend our single-band semi-parametric Gaussian process modeling of Mira light curves to a multiband version and obtain improved period determinations. We use our previous results on near-infrared properties of candidate Miras in the LMC to classify the majority of the M33 sample into oxygen- or carbon-rich subsets. We derive period–luminosity relations for O-rich Miras and determine a distance modulus for M33 of 24.80 ± 0.06 mag.