<i>vbyCa</i>Hβ CCD Photometry of Clusters. VIII. The Super-Metal-Rich, Old Open Cluster NGC 6791

Anthony-Twarog, Barbara J.; Twarog, Bruce A.; Mayer, L.

doi:10.1086/511976

Cited by 49 publications

(69 citation statements)

References 69 publications

(182 reference statements)

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“…NGC 6791 is one of the oldest, most massive and most metalrich open clusters known (Origlia et al 2006;Carretta et al 2007;Anthony-Twarog et al 2007), and contains a population of hot blue stars (Liebert et al 1994;Landsman et al 1998) and white dwarfs extending to the end of the cooling sequence (Bedin et al 2005(Bedin et al , 2008Kalirai et al 2007). For these reasons NGC 6791 has been studied extensively.…”

Section: Ngc 6791mentioning

confidence: 99%

Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819, and NGC 6811 usingKepler

Hekker

Basu

Stello

et al. 2011

A&A

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Context. Four open clusters are present in the Kepler field of view and timeseries of nearly a year in length are now available. These timeseries allow us to derive asteroseismic global oscillation parameters of red-giant stars in the three open clusters NGC 6791, NGC 6819 and NGC 6811. From these parameters and effective temperatures, we derive masses, radii and luminosities for the clusters as well as field red giants. Aims. We study the influence of evolution and metallicity on the observed red-giant populations. Methods. The global oscillation parameters are derived using different published methods and the effective temperatures are derived from 2MASS colours. The observational results are compared with BaSTI evolution models. Results. We find that the mass has significant influence on the asteroseismic quantities Δν vs. ν max relation, while the influence of metallicity is negligible, under the assumption that the metallicity does not affect the excitation/damping of the oscillations. The positions of the stars in the H-R diagram depend on both mass and metallicity. Furthermore, the stellar masses derived for the field stars are bracketed by those of the cluster stars. Conclusions. Both the mass and metallicity contribute to the observed difference in locations in the H-R diagram of the old metal-rich cluster NGC 6791 and the middle-aged solar-metallicity cluster NGC 6819. For the young cluster NGC 6811, the explanation of the position of the stars in the H-R diagram challenges the assumption of solar metallicity, and this open cluster might have significantly lower metallicity [Fe/H] in the range −0.3 to −0.7 dex. Also, nearly all the observed field stars seem to be older than NGC 6811 and younger than NGC 6791.

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Section: Ngc 6791mentioning

confidence: 99%

Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819, and NGC 6811 usingKepler

Hekker

Basu

Stello

et al. 2011

A&A

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“…The open cluster NGC 6791 is one of the oldest and, at the same time, the most metal-rich open clusters known (Origlia et al 2006;Carretta et al 2007; Anthony- Twarog et al 2007;Brogaard et al 2011, hereafter Paper I), and is therefore Photometric data are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/543/A106 very important for understanding chemical evolution and metalrich stars. In addition, it is a well-populated open cluster, with a (statistically) significant number of stars in all stages of evolution from the main sequence to the white dwarfs (King et al 2005;Bedin et al 2005Bedin et al , 2008a, as well as with numerous variable stars Mochejska et al 2002;de Marchi et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members

Brogaard

VandenBerg

Bruntt

et al. 2012

A&A

172

276

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Context. Models of stellar structure and evolution can be constrained by measuring accurate parameters of detached eclipsing binaries in open clusters. Multiple binary stars provide the means to determine helium abundances in these old stellar systems, and in turn, to improve estimates of their age. Aims. In the first paper of this series, we demonstrated how measurements of multiple eclipsing binaries in the old open cluster NGC 6791 sets tighter constraints on the properties of stellar models than has previously been possible, thereby potentially improving both the accuracy and precision of the cluster age. Here we add additional constraints and perform an extensive model comparison to determine the best estimates of the cluster age and helium content, employing as many observational constraints as possible. Methods. We improve our photometry and correct empirically for differential reddening effects. We then perform an extensive comparison of the new colour-magnitude diagrams (CMDs) and eclipsing binary measurements to Victoria and DSEP isochrones in order to estimate cluster parameters. We also reanalyse a spectrum of the star 2-17 to improve [Fe/H] constraints. Results. We find a best estimate of the age of ∼8.3 Gyr for NGC 6791 while demonstrating that remaining age uncertainty is dominated by uncertainties in the CNO abundances. The helium mass fraction is well constrained at Y = 0.30 ± 0.01 resulting in ΔY/ΔZ ∼ 1.4 assuming that such a relation exists. During the analysis we firmly identify blue straggler stars, including the star 2-17, and find indications for the presence of their evolved counterparts. Our analysis supports the RGB mass-loss found from asteroseismology and we determine precisely the absolute mass of stars on the lower RGB, M RGB = 1.15 ± 0.02 M . This will be an important consistency check for the detailed asteroseismology of cluster stars. Conclusions. Using multiple, detached eclipsing binaries for determining stellar cluster ages, it is now possible to constrain parameters of stellar models, notably the helium content, which were previously out of reach. By observing a suitable number of detached eclipsing binaries in several open clusters, it will be possible to calibrate the age-scale and the helium enrichment parameter Δ Y/Δ Z, and provide firm constraints that stellar models must reproduce.

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“…l and b are the Galactic longitude and latitude of the clusters; the symbol μ 0 indicates the true distance modulus of the cluster. References: (1) Gratton et al (1997); (2) Harris (2010); (3) Brasseur et al (2010); (4) Hodder et al (1992); (5) Sarajedini, Dotter, & Kirkpatrick (2009); (6) Hog & Flynn (1998); (7) Anthony-Twarog, Twarog, & Mayer (2007); (8) Sandage, Lubin, & VandenBerg (2003). [M/H] is the estimated error on the metallicity, for each set of derived T eff , log g and [M/H].…”

Section: Introductionmentioning

confidence: 99%

Absolute Magnitude Calibration for Red Giants Based on the Colour–Magnitude Diagrams of Galactic Clusters. III. Calibration with 2MASS

Karaali

Bilir²,

Gökçe³

2013

Publ. Astron. Soc. Aust.

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We present two absolute magnitude calibrations, M J and M K s , for red giants with the colour-magnitude diagrams of five Galactic clusters with different metallicities, i.e. M92, M13, M71, M67, and NGC 6791. The combination of the absolute magnitudes of the red giant sequences with the corresponding metallicities provides calibration for absolute magnitude estimation for red giants for a given colour

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vbyCaHβ CCD Photometry of Clusters. VIII. The Super-Metal-Rich, Old Open Cluster NGC 6791

Cited by 49 publications

References 69 publications

Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819, and NGC 6811 usingKepler

Asteroseismic inferences on red giants in open clusters NGC 6791, NGC 6819, and NGC 6811 usingKepler

Age and helium content of the open cluster NGC 6791 from multiple eclipsing binary members

Absolute Magnitude Calibration for Red Giants Based on the Colour–Magnitude Diagrams of Galactic Clusters. III. Calibration with 2MASS

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