NGC 6067: a young and massive open cluster with high metallicity

Alonso-Santiago, J.; Negueruela, I.; Marco, A.; Tabernero, H. M.; González-Fernández, C.; Castro, N.

doi:10.1093/mnras/stx783

Cited by 36 publications

(42 citation statements)

References 115 publications

(186 reference statements)

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“…This result might seem at odds with previous findings of a solar or sub-solar metallicity for young and intermediate-age clusters (see, e.g., D'Orazi et al 2011;Spina et al 2017, and references therein). However, it is in agreement with what is expected from standard chemical evolution (e.g., Minchev et al 2013, and references therein) and recent results of a super-solar metallicity ([Fe/H] ≈ +0.2) for some young or intermediate-age clusters in the solar neighborhood, such as NGC 6067 (Alonso-Santiago et al 2017) and Praesepe (D'Orazi et al 2019).…”

Section: Discussionsupporting

confidence: 91%

Stellar population astrophysics (SPA) with the TNG. Characterization of the young open cluster ASCC 123

Frasca

Alonso-Santiago

Catanzaro

et al. 2019

A&A

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Star clusters are key to understand the stellar and Galactic evolution. ASCC 123 is a little-studied, nearby and very sparse open cluster. We performed the first high-resolution spectroscopic study of this cluster in the framework of the SPA (Stellar Population Astrophysics) project with GIARPS at the TNG. We observed 17 stars, five of which turned out to be double-lined binaries. Three of the investigated sources were rejected as members on the basis of astrometry and lithium content. For the remaining single stars we derived the stellar parameters, extinction, radial and projected rotational velocities, and chemical abundances for 21 species with atomic number up to 40. From the analysis of single main-sequence stars we found an average extinction AV ≃ 0.13 mag and a median radial velocity of about −5.6 km s −1 . The average metallicity we found for ASCC 123 is [Fe/H]≃ +0.14 ± 0.04, which is in line with that expected for its Galactocentric distance. The chemical composition is compatible with the Galactic trends in the solar neighborhood within the errors. From the lithium abundance and chromospheric Hα emission we found an age similar to that of the Pleiades, which agrees with that inferred from the Hertzsprung-Russell and color-magnitude diagrams.

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Section: Discussionsupporting

confidence: 91%

Stellar population astrophysics (SPA) with the TNG. Characterization of the young open cluster ASCC 123

Frasca

Alonso-Santiago

Catanzaro

et al. 2019

A&A

Self Cite

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“…Taking the error weighted average of published cluster parameters (see Table.1) we find an age of 90 ± 20 million years, a distance of 1.88 ± 0.10 kpc, a reddening of E(B-V)= 0.35 ± 0.03, a tidal radius of 12.3 arcminutes and a heliocentric radial velocity of -39.79 ± 0.57 km/s. These are in excellent agreement with findings of the most recent cluster study 17 [20][21][22] for the adopted cluster parameters and accounting for the time since the star left the MS and passed through the AGB phase, predict a PN progenitor mass of 5.58 −0.43 +0.62 ⨀ . Such a high mass for a PN progenitor is unprecedented and provides a key new datum at the poorly studied IFMR high-mass end.…”

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confidence: 89%

A high-mass planetary nebula in a Galactic open cluster

et al. 2019

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Planetary Nebulae are the ionised ejected envelopes surrounding the remnant cores of dying stars. Theory predicts that main-sequence stars with one to about eight times the mass of our sun may eventually form planetary nebulae. Until now no example has been confirmed at the higher mass range. Here we report that planetary nebula BMP J1613-5406 is associated with Galactic star cluster NGC 6067. Stars evolving off the main sequence of this cluster have a mass around five solar masses. Confidence in the planetary nebula-cluster association comes from their tightly consistent radial velocities in a sightline with a steep velocity-distance gradient, common distances, reddening and location of the planetary nebula within the cluster boundary. This is an unprecedented example of a planetary nebular whose progenitor star mass is getting close to the theoretical lower limit of core-collapse supernova formation. It provides evidence supporting theoretical predictions that 5+ solar mass stars can form planetary nebulae. Further study should provide fresh insights into stellar and Galactic chemical evolution. Introduction and Background Stars live their lives as nuclear fusion reactors and their fate usually depends on birth mass. Massive stars burn their fuel quickly and can explode as supernovae after a few million years. The vast majority of stars have lower mass and live for many billions of years. Planetary Nebulae (PNe) may eventually form from stars of ~1-8 Mʘ. Such PNe progenitors represent 90% of all stars more massive than the sun. Towards the end of their lives most such stars pass through the Asymptotic Giant Branch (AGB) phase where the bulk of mass-loss occurs. A final, ejected envelope is ionized by the UV radiation field from the hot, remnant central star (CS) forming a

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“…These two clusters, at a galactocentric distances around 10 kpc, show a metallicity comparable to that of the LMC. Alonso-Santiago et al (2017) suggested that metallicity inhibits the formation of Cepheids. Nevertheless, the absence of Cepheids in low-metallicity environments such as NGC 2345 and NGC 3105 casts doubts on that possibility since both are massive enough clusters to serve as stellar evolution testbeds.…”

Section: Starmentioning

confidence: 99%

A comprehensive study of NGC 2345, a young open cluster with a low metallicity

Alonso-Santiago

Negueruela

Marco

et al. 2019

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Context. NGC 2345 is a young open cluster hosting seven blue and red supergiants, low metallicity and a high fraction of Be stars which makes it a privileged laboratory to study stellar evolution. Aims. We aim to improve the determination of the cluster parameters and study the Be phenomenon. Our objective is also to characterise its seven evolved stars by deriving their atmospheric parameters and chemical abundances. Methods. We performed a complete analysis combining for the first time ubvy photometry with spectroscopy as well as Gaia Data Release 2. We obtained spectra with classification purposes for 76 stars and high-resolution spectroscopy for an in-depth analysis of the blue and red evolved stars. Results. We identify a new red supergiant and 145 B-type likely members within a radius of 18.7±1.2 arcmin, which implies an initial mass, M cl ≈5 200 M . We find a distance of 2.5±0.2 kpc for NGC 2345, placing it at R GC =10.2±0.2 kpc. Isochrone fitting supports an age of 56±13 Ma, implying masses around 6.5 M for the supergiants. A high fraction of Be stars (≈10%) is found. From the spectral analysis we estimate for the cluster an average v rad =+58.6 ± 0.5 km s −1 and a low metallicity, [Fe/H]=−0.28±0.07. We also have determined chemical abundances for Li, O, Na, Mg, Si, Ca, Ti, Ni, Rb, Y, and Ba for the evolved stars. The chemical composition of the cluster is consistent with that of the Galactic thin disc. One of the K supergiants, S50, is a Li-rich star, presenting an A(Li)≈2.1. An overabundance of Ba is found, supporting the enhanced s-process. Conclusions. NGC 2345 has a low metallicity for its Galactocentric distance, comparable to typical LMC stars. It is massive enough to serve as a testbed for theoretical evolutionary models for massive intermediate-mass stars.

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NGC 6067: a young and massive open cluster with high metallicity

Cited by 36 publications

References 115 publications

Stellar population astrophysics (SPA) with the TNG. Characterization of the young open cluster ASCC 123

Stellar population astrophysics (SPA) with the TNG. Characterization of the young open cluster ASCC 123

A high-mass planetary nebula in a Galactic open cluster

A comprehensive study of NGC 2345, a young open cluster with a low metallicity

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