SIMBAD references

2020A&A...644A.136A - Astronomy and Astrophysics, volume 644A, 136-136 (2020/12-1)

Three open clusters containing Cepheids: NGC 6649, NGC 6664, and Berkeley 55.


Abstract (from CDS):

Classical Cepheids in open clusters play an important role in benchmarking stellar evolution models, in addition to anchoring the cosmic distance scale and invariably securing the Hubble constant. Three pertinent clusters hosting classical Cepheids and red (super)giants are: NGC 6649, NGC 6664, and Berkeley 55. These clusters form the basis of analysis to assess newly acquired spectra (≃50), archival photometry, and Gaia DR2 data. Importantly, for the first time chemical abundances were determined for the evolved members of NGC 6649 and NGC 6664. We find that they are slightly metal-poor relative to the mean Galactic gradient. Also, an overabundance of Ba is observed. These two clusters likely belong to the thin disc and the latter finding supports the "s-enhanced" scenario of D'Orazi et al. (2009ApJ...693L..31D). NGC 6664 and Berkeley 55 exhibit radial velocities consistent with Galactic rotation, while NGC 6649 displays a peculiar velocity. The resulting age estimates for the clusters (≃70Ma) imply masses of ≃6M for the (super)giant demographic. Lastly, the observed yellow-to-red (super)giant ratio is lower than expected and the overall differences that are relative to the models reflect the outstanding theoretical uncertainties.

Abstract Copyright: © ESO 2020

Journal keyword(s): open clusters and associations: individual: NGC 6649 - open clusters and associations: individual: NGC 6664 - open clusters and associations: individual: Berkeley 55 - Hertzsprung-Russell and C-M diagrams - stars: abundances - stars: variables: Cepheids

Status at CDS : Objects in title, abstract, text, figures, and all or part of small table(s) being processed in SIMBAD.

CDS comments: Table 1 Star 52 in NGC 6649, star 228 in NGC 6664 and star A in NGC 6664 are not identified.

Simbad objects: 108

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