Astron. J., 145, 134 (2013/May-0)
Ruprecht 147: the oldest nearby open cluster as a new benchmark for stellar astrophysics.
CURTIS J.L., WOLFGANG A., WRIGHT J.T., BREWER J.M. and JOHNSON J.A.
Abstract (from CDS):
Ruprecht 147 is a hitherto unappreciated open cluster that holds great promise as a standard in fundamental stellar astrophysics. We have conducted a radial velocity survey of astrometric candidates with Lick, Palomar, and MMT observatories and have identified over 100 members, including 5 blue stragglers, 11 red giants, and 5 double-lined spectroscopic binaries (SB2s). We estimate the cluster metallicity from spectroscopic analysis, using Spectroscopy Made Easy (SME), and find it to be [M/H] = +0.07±0.03. We have obtained deep CFHT/MegaCam g'r'i'z' photometry and fit Padova isochrones to the (g' - i') and Two Micron All Sky Survey (J - KS) color-magnitude diagrams, using the τ2 maximum-likelihood procedure of Naylor, and an alternative method using two-dimensional cross-correlations developed in this work. We find best fits for Padova isochrones at age t = 2.5±0.25 Gyr, m - M = 7.35 ±0.1, and AV= 0.25±0.05, with additional uncertainty from the unresolved binary population and possibility of differential extinction across this large cluster. The inferred age is heavily dependent on our choice of stellar evolution model: fitting Dartmouth and PARSEC models yield age parameters of 3 Gyr and 3.25 Gyr, respectively. At ∼300 pc and ∼3 Gyr, Ruprecht 147 is by far the oldest nearby star cluster.
open clusters and associations: general - open clusters and associations: individual: Ruprecht 147
VizieR on-line data:
<Available at CDS (J/AJ/145/134): table3.dat>
Table 3: [CWW2013] NNN (Nos 1-108).
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