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

Abstract

Classical Cepheids in open clusters play an important role in benchmarking stellar evolution models, anchoring the cosmic distance scale, and invariably securing the Hubble constant. NGC 6649, NGC 6664 and Berkeley 55 are three pertinent clusters that host classical Cepheids and red (super)giants, and an analysis was consequently initiated to assess newly acquired spectra ($\approx$50), archival photometry, and $Gaia$ DR2 data. Importantly, for the first time chemical abundances are 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, and an overabundance of Ba is observed. Those clusters likely belong to the thin disc, and the latter finding supports D'Orazi et al. (2009) "$s$-enhanced" scenario. 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 ($\approx$70 Ma) imply masses for the (super)giant demographic of $\approx$6 M${}_{sun}$. Lastly, the observed yellow-to-red (super)giant ratio is lower than expected, and the overall differences relative to models reflect outstanding theoretical uncertainties.

arXiv comment24 pages, 15 tables and 13 figures. Accepted for publication in A&A

References in corpus (64)

• emcee: The MCMC Hammer
• Gaia Data Release 2. Summary of the contents and survey properties
• On the variation of the Initial Mass Function
• PARSEC: stellar tracks and isochrones with the PAdova and TRieste Stellar Evolution Code
• A grid of MARCS model atmospheres for late-type stars I. Methods and general properties
• Gaia Data Release 2: The astrometric solution
• Large Magellanic Cloud Cepheid Standards Provide a 1% Foundation for the Determination of the Hubble Constant and Stronger Evidence for Physics Beyond LambdaCDM
• Grids of stellar models with rotation - I. Models from 0.8 to 120 Msun at solar metallicity (Z = 0.014)
• Trigonometric Parallaxes of High Mass Star Forming Regions: the Structure and Kinematics of the Milky Way
• Astrophysics Source Code Library
• Tensions between the Early and the Late Universe
• Global survey of star clusters in the Milky Way II. The catalogue of basic parameters
• A Gaia DR2 view of the Open Cluster population in the Milky Way
• Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program.Galactic stellar populations and planets
• New physics in light of the $H_0$ tension: an alternative view
• HERMES: a high-resolution fibre-fed spectrograph for the Mercator telescope
• Determining stellar atmospheric parameters and chemical abundances of FGK stars with iSpec
• The Expansion of the Universe is Faster than Expected
• Atmospheric NLTE-Models for the Spectroscopic Analysis of Blue Stars with Winds. II. Line-Blanketed Models
• Calibration of the Tip of the Red Giant Branch (TRGB)
• Improved spectroscopic parameters for transiting planet hosts
• The IACOB project: I. Rotational velocities in Northern Galactic O and early B-type stars revisited. The impact of other sources of line-broadening
• On the triple origin of blue stragglers
• On the metallicity of open clusters. III. Homogenised sample
• Chemical abundances of 1111 FGK stars from the HARPS GTO planet search program II: Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd and Eu
• On the fine structure of the Cepheid metallicity gradient in the Galactic thin disk
• The Evolutionary Status of Be Stars: Results from a Photometric Study of Southern Open Clusters
• On the Effect of Rotation on Populations of Classical Cepheids II. Pulsation Analysis for Metallicities 0.014, 0.006, and 0.002
• Classical Cepheid Pulsation Models. X. The Period-Age Relation
• Rate of Period Change as a Diagnostic of Cepheid Properties
• Enhanced production of barium in low-mass stars: evidence from open clusters
• Lithium and zirconium abundances in massive Galactic O-rich AGB stars
• GAIA Cepheid parallaxes and 'Local Hole' relieve $H_0$ tension
• CCD BV survey of 42 open clusters
• Oxygen abundances in G- and F-type stars from HARPS
• On the effect of rotation on populations of classical Cepheids I. Predictions at solar metallicity
• The Cepheid period -- luminosity -- metallicity relation based on Gaia DR2 data
• A Multi-Membership Catalogue for 1876 Open Clusters using UCAC4 data
• Consistent metallicity scale for cool dwarfs and giants. A benchmark test using the Hyades
• On the alpha-element gradients of the Galactic thin disk using Cepheids
• The ARAUCARIA project: Grid-Based Quantitative Spectroscopic Study of Massive Blue Stars in NGC55
• The IACOB project: A grid-based automatic tool for the quantitative spectroscopic analysis of O-stars
• An LTE effective temperature scale for red supergiants in the Magellanic clouds
• Be phenomenon in open clusters: Results from a survey of emission-line stars in young open clusters
• On the metallicity distribution of classical Cepheids in the Galactic inner disk
• The Accuracy of the Hubble Constant Measurement Verified through Cepheid Amplitudes
• On the Blue Loops of Intermediate-Mass Stars
• On the Application of Wesenheit Function in Deriving Distance to Galactic Cepheids
• NGC 6067: a young and massive open cluster with high metallicity
• Variability of Be Stars in Southern Open Clusters
• Distances to Cepheid Open Clusters Via Optical and K-Band Imaging
• Tool for Automatic Measurement of Equivalent width (TAME)
• Barium and Yttrium abundance in intermediate-age and old open clusters
• Line profile variations in classical Cepheids. Evidence for non-radial pulsations?
• A comprehensive study of NGC 2345, a young open cluster with a low metallicity
• New Evidence Supporting Cluster Membership for the Keystone Calibrator Delta Cephei
• Rubidium abundances in the globular clusters NGC 6752, NGC 1904 and NGC 104 (47 Tuc)
• Anchors for the Cosmic Distance Scale: the Cepheid QZ Normae in the Open Cluster NGC 6067
• Seven Problems with the Claims Related to the Hubble Tension in arXiv:1810.02595
• Berkeley 51, a young open cluster with four yellow supergiants
• NGC 3105: a young open cluster with low metallicity
• The young open cluster Berkeley 55
• New Cepheid variables in the young open clusters Berkeley 51 and Berkeley 55
• On the Paradoxical Impact of Blending by Red Clump Giants

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• SteParSyn: A Bayesian code to infer stellar atmospheric parameters using spectral synthesis
• The origin of early-type runaway stars from open clusters
• Stellar Population Astrophysics (SPA) with the TNG: Stock 2, a little-studied open cluster with an eMSTO
• Galactic open cluster Cepheids -- a census based on Gaia EDR3
• Search for Classical Cepheids in Galactic Open Clusters and Calibration of the Period Wesenheit Metallicity Relation in the Gaia Bands
• MAGIS (Measuring Abundances of red super Giants with Infrared Spectroscopy) project I. Establishment of an abundance analysis procedure for red supergiants and its evaluation with nearby stars
• A massive open cluster hiding in full sight
• The Radcliffe Wave as traced by young open clusters: Stellar parameters, activity indicators, and abundances of solar-type members of eight young clusters
• Gaia colour-magnitude diagrams of young open clusters: Identification in the UBC catalogue and a comparison of manual and automated analysis
• UBVI CCD Photometry of Berkeley 55 Open Cluster
• A Near-Infrared and Optical Study of NGC 5822: An Open Cluster Hosting Barium-stars and Lithium-Enriched Giant Stars