A Search for Stars Physically Associated with the 16 Day Cepheid X Cygni. II. Clusters in the Field

Abstract

A photometric UBV study is presented for the cluster Ruprecht 175 and the southern portion of the cluster Ruprecht 173, both of which lie in the field of the 16.38 day Cepheid X Cyg. Photoelectric observations for 81 stars and photographic observations for another 142 stars are used with spectroscopic CCD observations for bright cluster stars to investigate the reddening and distance of the Ruprecht 173s/175 complex. The reddening law is described by the relation EU - B/EB - V = 0.75, and the ratio of total to selective extinction for the dust clouds in this region of Cygnus is characterized by R ≡ AV/EB - V = 3.00 ± 0.09 s.e. The dust that obscures most cluster stars is ~700 pc distant, whereas the cluster complex Ruprecht 173s/175 is located at a distance of 1.22 ± 0.02 kpc (V0 - MV = 10.43 ± 0.04 s.e.). The cluster complex is very poorly populated and contains only 29 likely B-, A- and F-type members to our survey limit. X Cyg shares a partial spatial coincidence with cluster stars, as well as an inferred similarity in evolutionary status. Its derived luminosity as a cluster member is MV = -4.87 ± 0.07 s.e., and its derived space reddening is EB - V = 0.25 ± 0.02 [EB - V(B0) = 0.28 ± 0.02]. The case for cluster membership is not conclusive, however, and requires confirmation from radial velocity data.