CCD Stromgren studies in NGC 6397

Abstract

view Abstract Citations (33) References (56) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS CCD Stromgren Studies in NGC 6397 Anthony-Twarog, Barbara J. ; Twarog, Bruce A. ; Suntzeff, Nicholas B. Abstract Six fields in NGC 6397 are studied with CCD photometry in the Stromgren y, b, and v systems to expand the number of sampled photometric binaries and study their characteristics. The fiducial sequences for the cluster are determined to assess the binary population, and the fiducial CMD is analyzed to constrain the cluster age and distance. The distribution of the m(1) (b - y) diagram yields potential members, and about 7 percent of the main-sequence members are characterized as composites. An apparent distance modulus of (m - M) = 12.1 is derived from the reddening and Fe/H values, and these values lead to an age of more than 18 x 10 exp 9 yr from the luminosity of the turnoff. The standard main-sequence relations developed by McClure et al. (1987) and Sarajedini and King (1987) are compared to the present values. NGC 6397 is concluded to be one of the oldest clusters in a globular sample with an age spread of 5-6 x 10 exp 9 yr and assumed to reside in the old tail of a broad globular cluster-age distribution. Publication: The Astronomical Journal Pub Date: April 1992 DOI: 10.1086/116140 Bibcode: 1992AJ....103.1264A Keywords: Globular Clusters; Main Sequence Stars; Stellar Composition; Stellar Spectrophotometry; Ubv Spectra; Binary Stars; Charge Coupled Devices; Color-Magnitude Diagram; Metallicity; Stellar Luminosity; Stellar Parallax; Astrophysics; GLOBUALR CLUSTERS: INDIVIDUAL: NGC 6397; TECHNIQUES: PHOTOMETRY full text sources ADS | data products SIMBAD (14)