SIMBAD references

We present multi-epoch infrared photometry in the K_s-band for 74 bright RR Lyrae variable stars tied directly to the Two-Micron All-Sky Survey (2MASS) photometric system. We systematize additional K-band photometry from the literature to the 2MASS system and combine it to obtain photometry for 146 RR Lyrae stars on a consistent, modern system. A set of outlier stars in the literature photometry is identified and discussed. Reddening estimates for each star are gathered from the literature and combined to provide an estimate of the interstellar absorption affecting each star, and we find excellent agreement with another source in the literature. We utilize trigonometric parallaxes from the Second Data Release of the European Space Agency's Gaia astrometric satellite to determine the absolute magnitude, M_Ks_ for each of these stars, and analyze them using the astrometry-based luminosity prescription to obtain a parallax-based calibration of M_K(RR). Our period-luminosity-metallicity relationship is M_Ks_=(-2.8±0.2)(logP+0.27) + (0.12 ± 0.02) ([Fe/H] + 1.3) - (0.41 ± 0.03) mag. A Gaia global zero-point error of π_zp = -0.042 ± 0.013 mas is determined for this sample of RR Lyrae stars.