CCD Washington photometry of four poorly studied open clusters in the two inner quadrants of the galactic plane

Abstract

Complementing our Washington photometric studies on Galactic open clusters (OCs), we now focus on four poorly studied OCs located in the first and fourth Galactic quadrants, namely BH84, NGC5381, BH211 and Czernik37. We have obtained CCD photometry in the Washington system C and T1 passbands down to T1∼8.5mag for these four clusters. Their positions and sizes were determined using the stellar density radial profiles. We derived reddening, distance, age and metallicity of the clusters from extracted (C-T1,T1) color-magnitude diagrams (CMDs), using theoretical isochrones computed for the Washington system. There are no previous photometric data in the optical band for BH84, NGC5381 and BH211. The CMDs of the observed clusters show relatively well defined main sequences, except for Czernik37, wherein significant differential reddening seems to be present. The red giant clump is clearly seen only in BH211. For this cluster, we estimated the age in (1000-200+260)Myr, assuming a metallicity of Z=0.019. BH84 was found to be much older than it was previously believed, while NGC5381 happened to be much younger than previously reported. The heliocentric distances to these clusters are found to range between 1.4 and 3.4kpc. BH84 appears to be located at the solar galactocentric distance, while NGC5381, BH211 and Czernik37 are situated inside the solar ring.