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1994PASP..106..281D - Publ. Astron. Soc. Pac., 106, 281-308 (1994/March-0)
A photometric and radial-velocity analysis of the intermediate-age open cluster NGC 752.
DANIEL S.A., LATHAM D.W., MATHIEU R.D. and TWAROG B.A.
Abstract (from CDS):
Due to its age and the comprehensive data available for the cluster, NGC 752 provides an ideal test of a variety of evolutionary phenomena. Comparison with theoretical isochrones normalized in an internally consistent manner leads to the conclusion that the morphology and distribution of stars in the cmd can best be matched using models that include convective overshoot, particularly those of Schaller et al. (1992). Despite their differences, the traditional and the overshoot isochrones both imply very similar ages, 1.9 ± 0.2 Gyr and 1.7 ± 0.1 Gyr, respectively, for the cluster. The Li abundances for the giants confirm that the giant branch is dominated by clump stars and first-ascent giants below the luminosity of the clump. The position and size of the Li dip among the main sequence stars, compared to the Hyades, is readily explained by stellar evolution with convective overshoot. It is predicted that among turnoff stars in the intermediate-age range Li will cease to be a unique function of age at a given color. Chromospheric flux is shown to be a well-defined function of color for single, unevolved stars, identical to that found for the Hyades, and the relation for NGC 752 falls within the Vaughan-Preston gap. However, the slope of the relation requires that increasing color implies increasing age for the bluer portion of hte weak-emission boundary. The combined effect of small samples, random errors, emission limits, a possible selection bias in favor of turnoff stars, and metallicity corrections is to render highly questionable any interpretation of time-variable star formation within the Galaxy based upon chromosopheric ages.
Abstract Copyright: ∼
Journal keyword(s):
VizieR on-line data: <Available at CDS (J/PASP/106/281): tables.dat>
Nomenclature: Cl* NGC 752 DLM NNNA (Nos 162A, 162B, 167A, 172A, 285A, 285B), Cl* NGC 752 DLM NNNa (No. 167a), added to 1926AN....227..193H
CDS comments: in ref list: Barry 1987ApJ.315.264 instead 315.1987
Simbad objects: 257