uvbyCaHβ CCD photometry of clusters. VII. The intermediate-age anticenter cluster Melotte 71.
TWAROG B.A., CORDER S. and ANTHONY-TWAROG B.J.
Abstract (from CDS):
CCD photometry on the intermediate-band uvbyCaHβ system is presented for the anticenter, intermediate-age open cluster Melotte 71. Restricting the data to probable single members of the cluster using the color-magnitude diagram and the photometric indices alone generates a sample of 48 F dwarfs on the unevolved main sequence. The average E(b-y)=0.148±0.003 (standard error of the mean [s.e.m.]) or E(B-V)=0.202±0.004 (s.e.m.), where the errors refer to internal errors alone. With this reddening, [Fe/H] is derived from both m1and hk, using Hβ and b-y as the temperature index, with excellent agreement among the four approaches and a final weighted average of [Fe/H]=-0.17±0.02 (s.e.m.) for the cluster, on a scale in which the Hyades has [Fe/H]=+0.12. When adjusted for the higher reddening estimate, the previous metallicity estimates from Washington photometry and from spectroscopy are now in agreement with the intermediate-band result. From comparisons to isochrones of appropriate metallicity, the cluster age and distance are determined as 0.9±0.1 Gyr and (m-M)=12.2±0.1 or (m-M)0=11.6±0.1. At this distance from the Sun, Mel 71 has a galactocentric distance of 10.0 kpc on a scale in which the Sun is 8.5 kpc from the Galactic center. Based on its age, distance, and elemental abundances, Mel 71 appears to be a less populous analog to NGC 3960.
open clusters and associations: individual (Melotte 71) - Stars: Fundamental Parameters