Optical and Near-infrared Pulsation Properties of RR Lyrae and Population II Cepheid Variables in the Messier 15 Globular Cluster

Messier 15 (NGC 7078) is an old and metal-poor post core-collapse globular cluster which hosts a rich population of variable stars. We report new optical ($gi$) near-infrared (NIR, $JK_s$) multi-epoch observations for 129 RR Lyrae, 4 Population II Cepheids (3 BL Herculis, 1 W Virginis), anomalous Cepheid candidate in M15 obtained using the MegaCam WIRCam instruments on 3.6-m Canada-France-Hawaii Telescope. Multi-band data are used to improve periods classification stars, determine accurate mean magnitudes pulsational amplitudes from light curves fitted with NIR templates. derive period-luminosity relations Lyrae stars best constrained $K_s$-band, $m_{K_s} = -2.333~(0.054) \log P + 13.948~(0.015)$ scatter only $0.037$ mag. Theoretical empirical calibrations period-luminosity-metallicity true distance modulus M15: $15.196~\pm~0.026$~(statistical)~$\pm~ 0.039$~(systematic) Our precise moduli based variables mutually consistent agree recent measurements literature {\it Gaia} parallaxes other independent methods.