Near-Infrared Observations of RR Lyrae Variables in Galactic Globular Clusters. I. The Case of M92

Abstract

We present near-infrared (NIR) J-, H-, and K-band time series observations of the Galactic globular cluster (GGC) M92. On the basis of these data, we derive well-sampled light curves for 11 out of the 17 cluster RR Lyrae variables and, in turn, accurate mean NIR magnitudes. The comparison between the predicted and empirical slopes of the NIR period-luminosity (PL) relations indicates a very good agreement. Cluster distance determinations based on independent theoretical NIR PL relations present uncertainties smaller than 5% and agree quite well with recent distance estimates based on different distance indicators. We also obtain accurate and deep NIR color-magnitude diagrams ranging from the tip of the red giant branch (RGB) down to the main-sequence turnoff. We detect the RGB bump, and the NIR luminosities of this evolutionary feature are, within theoretical and empirical uncertainties, in good agreement with each other.