WIYN Open Cluster Study LXXX: HDI CCD UBVRI Photometry of the Old Open Cluster NGC 7142 and Comparison to M67

We present UBVRI photometry of 8702 stars in a 0°5 × 0°5 field in the direction of NGC 7142, taken with the Half Degree Imager at the WIYN 0.9 m telescope, to improve knowledge of this cluster's basic parameters. Our photometry spans the ranges 10.6-20.4 mag in U, 10.6-22.0 mag in B, 10.0-21.8 mag in V, 9.2-20.7 mag in R, and 8.5-19.9 mag in I. Using color-color diagrams that employ all four color combinations that include U, versus B - V, we derive a reddening-metallicity relation for the cluster, with preferred values E(B - V) = 0.338 ± 0.031 mag for the left-edge fiducial of the main sequence and [Fe/H] = 0.0 ± 0.1 dex, where the Hyades cluster has been used as an unreddened reference cluster, the extinction relations of Cardelli have been employed, and the metallicity dependence of the Yonsei-Yale (Y²) isochrones has been assumed. Comparison of our data to the Y² isochrones in multiple color-magnitude diagrams (CMDs) yields distance-metallicity and age-metallicity relations, with preferred values of $m-M=12.65\pm 0.23$ mag and age = ${4.0}_{+1.3}^{-0.7}$ Gyr. Re-evaluation of the parameters of M67 using Stetson's UBVI photometry yields [Fe/H] = -0.02 ± 0.05 dex, E(B - V) = 0.04 ± 0.01 mag, m - M = 9.75 ± 0.03 mag, and age = 3.85 ± 0.17 Gyr; we thus find the metallicity and age of the two clusters to be indistinguishable. A semi-independent analysis adopting the parameters of M67 and shifting the fiducials of the two clusters in six CMDs until they match strongly corroborates the values listed above. The differences between our inferred parallaxes and the Gaia DR2 values are 87 ± 60 μas for NGC 7142 and 48 ± 15 μas for M67, consistent with previous studies. ^* The WIYN Observatory is a joint facility of the University of Wisconsin-Madison, Indiana University, the National Optical Astronomy Observatory and the University of Missouri.