Release 11.12 ("Hergest Ridge")

Gclusters :: Bibliographic item "gc537"

Article ID: gc537
AuthorAlcaino, G.
TitleThe metal-poor globular cluster NGC 6656
JournalAstronomy and Astrophysics Supplement Series, vol. 29, p. 383-395.
Year of publication1977 (on gclusters from 2017-05-25 12:35:27 )
AbstractColor-magnitude (CM) diagrams for the nearby southern globular cluster NGC 6656 are derived from photographic measurements of 374 stars calibrated against a UBV photoelectric sequence of 16 stars with V magnitudes of 8.61 to 16.18. The main features of a composite CM diagram for three rings of stars are shown to be typical of metal-poorness and to include a rather steep well-defined giant branch, a large sample of blue horizontal-branch stars with (B-V) colors of 0.15 to 0.45 magnitude, and a lack of red horizontal-branch stars. The periods of two long-period red giants and one RR Lyrae variable are measured, a true distance modulus of 12.67 magnitudes (equivalent to a distance of 3.42 kpc) is determined, and the cluster is estimated to be 0.45 kpc from the galactic plane and 5.73 kpc from the galactic center. Metallicity parameters are obtained which confirm the cluster's low metallicity.
TagsNGC 6656

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