VR CCD Photometry of Variable Stars in the Globular Cluster NGC 4147

Abstract

Abstract We present results of a search for variable stars in a region of the globular cluster NGC 4147 based on photometric observations with a 4K × 4K CCD imager mounted at the axial port of the recently installed 3.6 m Devasthal optical telescope at Aryabhatta Research Institute of Observational Sciences, Nainital, India. We performed time series photometry of NGC 4147 in the V and R bands, and identified 42 periodic variables in the region of NGC 4147, 28 of which have been detected for the first time. Seventeen variable stars are located within the half-light radius ≲0.′48, of which 10 stars are newly identified variables. Two of the 10 variables are located within the core radius ≲0.′09. Based on their location in the V/(V − R) color–magnitude diagram and variability characteristics, seven, eight, five, and one newly identified probable member variables are classified as RRc, EA/E, EW, and SX Phe, respectively. The metallicity of NGC 4147 estimated from the light curves of RRab and RRc stars with the help of Fourier decomposition is found to be characteristic of Oosterhoff II. The distance derived using the light curves of RRab stars is consistent with that obtained from the observed V/(V − R) color–magnitude diagram.