RUPRECHT 147: THE OLDEST NEARBY OPEN CLUSTER AS A NEW BENCHMARK FOR STELLAR ASTROPHYSICS

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 stra...

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Published inThe Astronomical journal Vol. 145; no. 5; pp. 1 - 26
Main Authors Curtis, Jason L, Wolfgang, Angie, Wright, Jason T, Brewer, John M, Johnson, John Asher
Format Journal Article
LanguageEnglish
Published United States 01.05.2013
Subjects
Age
ASTROPHYSICS
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
BENCHMARKS
Binary stars
Clusters
COLOR
CORRELATIONS
Fittings
MAXIMUM-LIKELIHOOD FIT
Open clusters
PHOTOMETRY
RADIAL VELOCITY
SKY
SPECTROSCOPY
STAR CLUSTERS
STAR EVOLUTION
TWO-DIMENSIONAL CALCULATIONS
Italy, Veneto, Padova
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Summary: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 = or - 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 - K sub(S)) color-magnitude diagrams, using the [tau] super(2) 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 + or - 0.25 Gyr, m - M - 7.35 + or - 0.1, and A sub(v) = 0.25 + or - 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.
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ISSN:0004-6256
1538-3881
1538-3881
DOI:10.1088/0004-6256/145/5/134