Three-color photometry of the metal-rich globular cluster NGC 6171

Abstract

view Abstract Citations (53) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Three-color photometry of the metal-riche globular cluster NGC 6171. Sandage, A. ; Katem, B. Abstract Photometry of 293 stars shows that NGC 6171 (aiooo = 16h29w7, a1955 = - 12C57 ) is a moderately strong-lined globular cluster of Morgan's metal class V. The color-magnitude diagram is considerably different in two characteristics from the diagrams of weak-line clusters of the halo: (1) the horizontal branch in NGC 6171 is heavily populated on the red side of the variable star gap; (2) the giant stars at (B - V)0 = +1.4 rise only 2 <) above the horizontal branch in contrast to the value of A V = 3"'0. that occurs in the weak-line halo clusters. The reddening is E(B - V) (Y 30 as determined by the three-color method using foreground field stars and checked by other methods. Adopting this value gives a very small ultraviolet ezcess of a(U - B) = +(Y <)6 + 0"'06 (A.D.) for the cluster giants. Comparison with ( 0W2 to ( O 3, which applies to the weak-line clusters, shows that the metal abundance for stars in NGC 6171 is closer to that of Hyades stars than to the halo globular clusters. NGC 6171 is the only known cluster visible from the north in moderate galactic latitudes where mainsequence photometry can eventually be used to calibrate the absolute magnitudes of globular-cluster giant stars and RR Lyrae variables which have such a small abundance anomaly. Publication: The Astrophysical Journal Pub Date: May 1964 DOI: 10.1086/147850 Bibcode: 1964ApJ...139.1088S full text sources ADS | data products SIMBAD (31) GCPD (1)