Strömgren-Hβ Photometry of the Rich Open Cluster NGC 6705 (M 11)

We present CCD uvby β, photometry of 1419 stars located in the central region of the rich Galactic open cluster NGC 6705 (M11). Our study utilizes photometric data obtained with the 0.9 m WIYN telescope at the Kitt Peak National Observatory. Based on more than 330 stars in the spectral range B–A3, we derive average color excess E ( b - y ) = 0.33( ± 0.033 s.d.; 0.004 s.e.), corresponding to E ( B - V ) = 0.45, and average distance modulus 11.30( ± 0.4 s.d.; 0.04 s.e.), corresponding to 1820 ± 30 s.e. pc. Using the F-type stars of the cluster main sequence, we estimate [Fe/H] = -0.06( ± 0.59 s.d.; 0.05 s.e.). Based on PARSEC isochrones for Z = 0.0167, the age of the cluster is estimated as 250 Myr. Moderate differential reddening at the amount of A V = 0.86 is detected. No evidence of extended star formation is found for this cluster.