A New Look at Open Cluster NGC 6520

Abstract

We use CCD and photoelectric photometry with Stromgren filters along with medium resolution spectra to investigate NGC 6520, an open cluster very nearly in the direction of the galactic center. We find an age of 60 Myr, a distance of 2 kpc, and an average reddening E(b-y) = 0.295, but which increases toward the south. The average heliocentric radial velocity of the B stars is -29 km/sec, while the velocity of the nearby Barnard 86 is about 0 (heliocentric, -11 km/sec compared to the LSR). This velocity difference amounts to about 1.8 kpc since the cluster formed, implying that it is extremely doubtful NGC 6520 is related to Barnard 86.