Survey for Transiting Extrasolar Planets in Stellar Systems: I. Fundamental Parameters of the Open Cluster Ngc 1245

We derive fundamental parameters for the old, rich open cluster NGC 1245 using BV I photometry from the MDM 1.3m and 2.4m telescopes. Based on detailed isochrone fitting, we find NGC 1245 has a slightly sub-solar metallicity, [Fe/H] = −0.05 ± 0.03 (statistical) ± 0.08 (systematic), and an age of 1.04 ± 0.02 ± 0.09 Gyr. In contrast to previous studies, we find no evidence for significant differential reddening. We determine an extinction of AV = 0.68 ± 0.02 ± 0.09 mag and a distance modulus of (m−M)0 = 12.27±0.02±0.12 mag, which corresponds to a distance of 2.8±0.2 Kpc. We derive a logarithmic mass-function slope for the cluster of α = −3.12 ± 0.27, where a Salpeter slope is α = −1.35. Fits to the radial surface-density profile yield a core radius of rc = 3.10± 0.52 arcmin (2.57 ± 0.47 pc). NGC 1245 is highly relaxed and contains a strongly mass segregated population. The mass function for the inner cluster has a very shallow slope, b = −0.56± 0.28. In contrast, the outer periphery of the cluster is enriched with low mass members and devoid of high mass members out to the tidal radius, rt = 20 arcmin (16.5 pc). Based on the observed surface-density profile and an extrapolated mass function, we derive a total cluster mass, M = 1300± 90± 170M⊙. Subject headings: stars: fundamental parameters — stars: luminosity function, mass function — open clusters and associations: individual (NGC 1245)