Seven-Color Photometry of the Open Cluster NGC 1647 Area

The area of the open cluster NGC 1647 in Taurus is investigated by CCD photometry in the Vilnius seven-color system. Magnitudes and color indices are determined for 433 stars down to V = 15.0 mag in the 45 arcmin diameter area. For 252 of them photometric spectral and luminosity classes, interstellar reddenings, extinctions and distances are obtained. According to the CDS WEBDA database, 89 of them have a high cluster membership probability. Their mean distance from the Sun is 555±74 pc, excluding four stars which seem to be field stars. The main sequence starts at spectral class B7 V which corresponds to a cluster age of about 150 million years. Cluster members show a differential interstellar extinction ranging from 0.8 to 1.8 mag. The mean extinction of the cluster stars is 1.12±0.25 mag. Interstellar extinction in the area is dominated by the Taurus dark cloud complex at 160 pc. Color excesses of individual stars correlate well with the 100 μm dust thermal emission intensity. The cluster shape is investigated by counting stars down to K=15.6 mag and is found to be elongated in the direction roughly perpendicular to the Milky Way, with the flattening ∼0.4.