SIMBAD references

2002AJ....124..364C - Astron. J., 124, 364-378 (2002/July-0)

M75, a globular cluster with a trimodal horizontal branch. I. Color-magnitude diagram.


Abstract (from CDS):

Deep UBVI photometry for a large field covering the distant globular cluster M75 (NGC 6864) is presented. We confirm a previous suggestion that M75 possesses a bimodal horizontal branch (HB) bearing striking resemblance to the well-known case of NGC 1851. In addition, we detect a third, smaller grouping of stars on the M75 blue tail, separated from the bulk of the blue HB stars by a gap spanning about 0.5 mag in V. Such a group of stars may correspond to the upper part of a very extended, though thinly populated, blue tail. Thus M75 appears to have a trimodal HB. The presence of the ``Grundahl jump'' is verified using the broadband U filter. We explore the color-magnitude diagram of M75 with the purpose of deriving the cluster's fundamental parameters and find a metallicity of [Fe/H]=-1.03±0.17 dex and -1.24±0.21 in the Carretta & Gratton and Zinn & West scales, respectively. We discuss earlier suggestions that the cluster has an anomalously low ratio of bright red giants to HB stars. A differential age analysis with respect to NGC 1851 suggests that the two clusters are essentially coeval.

Abstract Copyright:

Journal keyword(s): Stars: Blue Stragglers - Stars: Color-Magnitude Diagrams - Galaxy: Globular Clusters: Individual: Messier Number: M75 - Galaxy: Globular Clusters: Individual: NGC Number: NGC 6864 - Stars: Variables: RR Lyrae Variable - Stars: Horizontal-Branch

Nomenclature: Table 5: [CBF2002b] N=26.

Simbad objects: 8

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