A uvbyCaHβ analysis of the old open cluster, NGC 6819

Journal Article · Mon Sep 01 04:00:00 EDT 2014 · Astronomical Journal (New York, N.Y. Online)

DOI:https://doi.org/10.1088/0004-6256/148/3/51· OSTI ID:22342264

Anthony-Twarog, Barbara J.; Twarog, Bruce A. ^[1]

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1. Department of Physics and Astronomy, University of Kansas, Lawrence, KS 66045-7582 (United States)

NGC 6819 is a richly populated, older open cluster situated within the Kepler field. A CCD survey of the cluster on the uvbyCaHβ system, coupled with proper-motion membership, has been used to isolate 382 highly probable, single-star unevolved main-sequence members over a 20' field centered on the cluster. From 278 F dwarfs with high precision photometry in all indices, a mean reddening of E(b – y) = 0.117 ± 0.005 or E(B – V) = 0.160 ± 0.007 is derived, where the standard errors of the mean include both internal errors and the photometric zero-point uncertainty. With the reddening fixed, the metallicity derived from the same 278 stars is [Fe/H] = –0.116 ± 0.101 from m {sub 1} and –0.055 ± 0.033 from hk, for a weighted average of [Fe/H] = –0.06 ± 0.04, where the quoted standard errors of the mean include the internal errors from the photometric scatter plus the uncertainty in the photometric zero points. If metallicity is derived using individual reddening values for each star to account for potential reddening variation across the face of the cluster, the analogous result is unchanged. The cluster members at the turnoff of the color-magnitude diagram are used to test and confirm the recently discovered variation in reddening across the face of the cluster, with a probable range in the variation of ΔE(B – V) = 0.045 ± 0.015. With the slightly higher reddening and lower [Fe/H] compared to commonly adopted values, isochrone fitting leads to an age of 2.3 ± 0.2 Gyr for an apparent modulus of (m – M) = 12.40 ± 0.12.

• OSTI ID: 22342264
• Journal Information: Astronomical Journal (New York, N.Y. Online), Journal Name: Astronomical Journal (New York, N.Y. Online) Journal Issue: 3 Vol. 148; ISSN 1538-3881
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
ACCURACY
CHARGE-COUPLED DEVICES
COLOR
COMPARATIVE EVALUATIONS
METALLICITY
PHOTOMETRY
PROPER MOTION
STAR CLUSTERS
STARS
WEIGHT