O and Na abundance patterns in open clusters of the Galactic disk

Silva, G. M. De; Gibson, Brad K.; Lattanzio, John C.; Asplund, Martin

doi:10.1051/0004-6361/200912279

Cited by 65 publications

(72 citation statements)

References 47 publications

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“…On the other hand, Na-rich and O-poor stars that are common in GCs are rare among field stars (Carretta et al) and are possibly absent from open clusters (OCs, see e.g., de Silva et al 2009). A similar result is obtained for other light elements, such as C and N, see e.g., Martell & Smith (2009), Martell & Grebel (2010).…”

Section: Introductionmentioning

confidence: 73%

Searching for multiple stellar populations in the massive, old open cluster Berkeley 39

Bragaglia

Gratton

Carretta

et al. 2012

A&A

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The most massive star clusters include several generations of stars with a different chemical composition (mainly revealed by an Na-O anti-correlation) while low-mass star clusters appear to be chemically homogeneous. We are investigating the chemical composition of several clusters with masses of a few 10 4 M to establish the lower mass limit for the multiple stellar population phenomenon. Using VLT/FLAMES spectra we determine abundances of Fe, O, Na, and several other elements (α, Fe-peak, and neutron-capture elements) in the old open cluster Berkeley 39. This is a massive open cluster: M ∼ 10 4 M , approximately at the border between small globular clusters and large open clusters. Our sample size of about 30 stars is one of the largest studied for abundances in any open cluster to date, and will be useful to determine improved cluster parameters, such as age, distance, and reddening when coupled with precise, well-calibrated photometry. We find that Berkeley 39 is slightly metal-poor, [Fe/H] = −0.20, in agreement with previous studies of this cluster. More importantly, we do not detect any star-to-star variation in the abundances of Fe, O, and Na within quite stringent upper limits. The rms scatter is 0.04, 0.10, and 0.05 dex for Fe, O, and Na, respectively. This small spread can be entirely explained by the noise in the spectra and by uncertainties in the atmospheric parameters. We conclude that Berkeley 39 is a single-population cluster.

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Section: Introductionmentioning

confidence: 73%

Searching for multiple stellar populations in the massive, old open cluster Berkeley 39

Bragaglia

Gratton

Carretta

et al. 2012

A&A

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“…1). Regardless of whether these abundance enhancements are real or due to systematic errors, they have important implications (De Silva et al 2009); for example in the studies of chemical evolution of the Galactic bulge, when comparing the bulge with the disk, the same type of stars in both populations should be used. In the first studies of this kind employing high-resolution spectroscopy, this was not yet possible for a sufficient number of targets (Fulbright et al 2007;Lecureur et al 2007;Zoccali et al 2006).…”

Section: Discussionmentioning

confidence: 99%

Abundances and physical parameters for stars in the open clusters NGC 5822 and IC 4756

Pace¹,

Danziger

Carraro³

et al. 2010

A&A

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Context. Classical chemical analyses may be affected by systematic errors that would cause observed abundance differences between dwarfs and giants. For some elements, however, the abundance difference could be real. Aims. We address the issue by observing 2 solar-type dwarfs in NGC 5822 and 3 in IC 4756, and comparing their composition with that of 3 giants in either of the aforementioned clusters. We determine iron abundance and stellar parameters of the dwarf stars, and the abundances of calcium, sodium, nickel, titanium, aluminium, chromium, silicon, and oxygen for both the giants and dwarfs. For the dwarfs, we also estimate the rotation velocities, and and lithium abundances. We improve the cluster parameter estimates (distance, age, and reddening) by comparing existing photometry with new isochrones. Methods. We acquired UVES high-resolution, of high signal-to-noise ratio (S /N) spectra. The width of the cross correlation profiles was used to measure rotation velocities. For abundance determinations, the standard equivalent width analysis was performed differentially with respect to the Sun. For lithium and oxygen, we derived abundances by comparing synthetic spectra with observed line features. Results. We find an iron abundance for dwarf stars equal to solar to within the margins of error for IC 4756, and slightly above for NGC 5822 ([Fe/H] = 0.01 and 0.05 dex respectively). The 3 stars in NGC 4756 have lithium abundances between Log N(Li) ≈ 2.6 and 2.8 dex, the two stars in NGC 5822 have Log N(Li) ≈ 2.8 and 2.5, respectively. Conclusions. For sodium, silicon, and titanium, we show that abundances of giants are significantly higher than those of the dwarfs of the same cluster (about 0.15, 0.15, and 0.35 dex). Other elements may also undergo enhancement, but all within 0.1 dex. Indications of much stronger enhancements can be found using literature data. But artifacts of the analysis may be partly responsible for this.

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“…The NLTE-corrected abundances should be higher than the LTE-uncorrected ones: this should bring our [Na/Fe] LTE measurements to closer agreement with literature measurements. If the observed enhancement in [Na/Fe] should prove to be real for OC, this would set OC stars completely apart form disc stars (De Silva et al 2009). If the large spread were in addition intrinsic, this would suggest that light element chemical anomalies are similar, although much less pronounced, to those found in globular clusters.…”

Section: Ratios Of Na and Al And Anticorrelationsmentioning

confidence: 96%

“…They are not present in the field populations of the Milky Way and its surrounding dwarf galaxies, and they have only more recently been found in Fornax and LMC clusters (Letarte et al 2006;Johnson et al 2006;Mucciarelli et al 2009). Dedicated searches for anticorrelations in OC include that of Martell & Smith (2009), on the strength of CH and CN bands in NGC 188, NGC 2158, and NGC 7789, that of Smiljanic et al (2009), based on high resolution spectroscopy of C, N, O, Na, and 12 C/ 13 C and that of De Silva et al (2009), which compiles and homogenizes literature Na-O high resolution data. No clear-cut sign of any anticorrelation has yet been found.…”

Section: Ratios Of Na and Al And Anticorrelationsmentioning

confidence: 99%

Chemical abundance analysis of the open clusters Cr 110, NGC 2099 (M 37), NGC 2420, NGC 7789, and M 67 (NGC 2682)

Pancino

Carrera

Rossetti

et al. 2010

A&A

196

206

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Context. The present number of Galactic Open Clusters that have high resolution abundance determinations, not only of [Fe/H], but also of other key elements, is largely insufficient to enable a clear modeling of the Galactic Disk chemical evolution. Aims. To increase the number of Galactic Open Clusters with high quality measurements. Methods. We obtained high resolution (R∼30 000), high quality (S/N∼50-100 per pixel), echelle spectra with the fiber spectrograph FOCES, at Calar Alto, Spain, for three red clump stars in each of five Open Clusters. We used the classical Equivalent Width analysis method to obtain accurate abundances of sixteen elements: Al,

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O and Na abundance patterns in open clusters of the Galactic disk

Cited by 65 publications

References 47 publications

Searching for multiple stellar populations in the massive, old open cluster Berkeley 39

Searching for multiple stellar populations in the massive, old open cluster Berkeley 39

Abundances and physical parameters for stars in the open clusters NGC 5822 and IC 4756

Chemical abundance analysis of the open clusters Cr 110, NGC 2099 (M 37), NGC 2420, NGC 7789, and M 67 (NGC 2682)

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