UBVI CCD photometry of M11 - II. New photometry and surface density profiles

Abstract

Extensive UBVI CCD photometry has been obtained for the intermediate-age open cluster M11 (NGC 6705). From this new photometry we derive the cluster parameters [V0 - Mv = 11.55 ± 0.10, E(B - V) = 0.428 ± 0.027 and radius = 16 arcmin] and age (log tage = 8.4 ± 0.1). We also derive density profiles and confirm the mass segregation in M11. The slope of the mass function increases systematically with increasing radius from the centre. We also confirm the existence of main-sequence field stars having similar photometric characteristics to M11. A large population of field red giant stars is also found in the observed fields.