Kinematics and CMD of the globular cluster NGC 4147

Abstract

Astrometry and BVRI CCD photometry of 115 stars down to in the region of about around the globular cluster NGC 4147 was performed. In the astrometric reduction, three earlier epoch plates taken at Sheshan, Shanghai, China, in 1958 and four recent epoch B -passband CCD frames taken at Kavalur, India, were used. The data were reduced to a catalogue based on measurements of stars on seven plates with an epoch period from 1917 to 1979 taken in Bonn, Germany, and ultimately to the Hipparcos catalogue. The reduction was done with the central overlapping method. Based on the new proper motion data, the membership probabilities of 115 stars were determined. Furthermore, three colour-magnitude diagrams (CMD) of V versus , and , respectively, for HB and GB stars were constructed from CCD photometry obtained with the Vainu Bappu Telescope. An absolute proper motion of the cluster of -2.08 ± 0.48 mas/yr in right ascension and -3.07 ± 0.46 mas/yr in declination has been obtained. The space velocity and apogalactic distance of the cluster with respect to the Galactic standard of rest were calculated. In contrast to the first results given in the literature we obtain a significantly lower velocity and a smaller apogalactic distance for NGC 4147.