RR Lyrae and Type II Cepheid Variables in Globular Clusters: Optical and Infrared Properties

Globular clusters are both primary fossils of galactic evolution and formation ideal laboratories for constraining the low-mass metal-poor stars. RR Lyrae type II Cepheid variables low-mass, radially pulsating stars that trace old-age stellar populations. These standard candles in globular crucial measuring their precise distances and, turn, absolute ages, calibration extragalactic distance scale. Herein, evolutionary stages Cepheids discussed, pulsation properties, including light curves, color–magnitude period–amplitude diagrams, period–luminosity relations at optical infrared wavelengths presented. The visual magnitude–metallicity relation multiband period–luminosity–metallicity covering a wide metallicity range also discussed detail application to Lyrae-based