2024JAVSO..52...43V

Images of the Messier 13 (M13/NGC 6205) globular cluster were requested from the Las Cumbres Global Observatory's 40-centimeter telescope to investigate the chemical composition and characteristics of the cluster along with three of its RR Lyrae variable stars. Gaia Data Release 3 data were used to fit an isochrone by varying parameters such as distance, reddening, metallicity, and age. The estimates obtained for these parameters were within uncertainty of the corresponding literature values despite a large range of metallicities that gave an appropriate fit; however, a significantly different proper motion in Right Ascension was used to screen for cluster membership. In addition, the periods for three of the RR Lyrae stars – V8, V31, V54 – were confirmed using phase dispersion minimization (string length and standard deviation methods) as well as the Lomb-Scargle method. The colors of three RR Lyrae stars were also investigated through color analysis using data in the Johnson-Cousins V and Sloan Digital Sky Survey I-prime filters. ASAS-SN Sky Patrol data were used to determine if two select stars, V8 and V31, were undergoing period evolution. Because of inconclusive data, further investigation is suggested. Finally, the period-luminosity-metallicity (PLM) relationship was applied to recompute the distance to the cluster. The average derived PLM distance of 7.1 kpcs was a close match to previous distance estimates from the literature.