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

Pace, G.; Danziger, John; Carraro, G.; Meléndez, Jorge; François, P.; Matteuccí, F.; Santos, N. C.

doi:10.1051/0004-6361/200913029

Cited by 25 publications

(36 citation statements)

References 58 publications

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“…We also determined the abundance of Ca, Ti and Si in stars where lines were detectable using the linelist of Pace et al (2010). We finally obtained the abundance of Ca in 76 stars, the abundance of Ti in 33 stars, and the abundance of Si in 13 stars.…”

Section: Elemental Abundance Of Other Elementsmentioning

confidence: 99%

Lithium abundance in the metal-poor open cluster NGC 2243

François¹,

Pasquini²,

Biazzo³

et al. 2013

A&A

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Context. Lithium is a fundamental element for studying the mixing mechanisms acting in the stellar interiors, for understanding the chemical evolution of the Galaxy and the Big Bang nucleosynthesis. The study of Li in stars of open clusters (OC) allows a detailed comparison with stellar evolutionary models and permits us to trace its galactic evolution. The OC NGC 2243 is particularly interesting because of its low metallicity ([Fe/H] = −0.54 ± 0.10 dex). Aims. We measure the iron and lithium abundance in stars of the metal-poor OC NGC 2243. The first aim is to determine whether the Li dip extends to such low metallicities, the second is to compare the results of our Li analysis in this OC with those present in 47 Tuc, a globular cluster of similar metallicity. Methods. We performed a detailed analysis of high-resolution spectra obtained with the multi-object facility FLAMES at the ESO VLT 8.2 m telescope. Lithium abundance was derived through line equivalent widths and the OSMARCS atmosphere models. Iron abundances from Fe i and Fe ii lines have also been measured and used to check the atmospheric model parameters.Results. The Li line is detected in 27 stars confirmed as likely cluster members by repeated radial velocity measurements. We determine a Li dip center of 1.06 M , which is much smaller than that observed in solar metallicity and metal-rich clusters. This finding confirms and strengthens the conclusion that the mass of the stars in the Li dip strongly depends on stellar metallicity. The mean Li abundance of the cluster is log n(Li) = 2.70 dex, which is substantially higher than that observed in 47 Tuc. We estimated an iron abundance of [Fe/H] = −0.54 ± 0.10 dex for NGC 2243, which is similar (within the errors) to previous findings. The [α/Fe] content ranges from 0.00 ± 0.14 for Ca to 0.20 ± 0.22 for Ti, which is low when compared to thick disk stars and to Pop II stars, but compatible with thin disk objects. We found a mean radial velocity of 61.9 ± 0.8 km s −1 for the cluster. Conclusions. We confirm a correlation between the Li dip cool-side position in mass as a function of the cluster's [Fe/H]. The Li abundance found in the metal-poor OC NGC 2243 agrees well with results obtained for the interstellar medium in the Small Magellanic Cloud having similar low metallicity. This value of Li is comparable to the primordial Li abundance deduced from WMAP measurements, therefore putting strong constraints on the models of Li enrichment during the early history of our Galaxy.

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Section: Elemental Abundance Of Other Elementsmentioning

confidence: 99%

Lithium abundance in the metal-poor open cluster NGC 2243

François¹,

Pasquini²,

Biazzo³

et al. 2013

A&A

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“…Pasquini et al (2004) investigated dwarfs and giants of the intermediate-age cluster IC 4651, and found, in general, excellent agreement between stars of different evolutionary status. Pace et al (2010) investigated the metallicity of five dwarfs and three giants in two open clusters and found differences in the metallicity of up to 0.10 dex for one of the clusters. They also pointed out enhancements of sodium, aluminium, and silicon for the giants.…”

Section: Introductionmentioning

confidence: 99%

Consistent metallicity scale for cool dwarfs and giants

Dutra-Ferreira

Pasquini

Smiljanić

et al. 2015

A&A

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Context. In several instances chemical abundances of main-sequence and giant stars are used simultaneously under the assumption that they share the same abundance scale. This assumption, if wrong, might have important implications in different astrophysical contexts. Aims. It is therefore crucial to understand whether the metallicity or abundance differences among dwarfs and giants are real or are produced by systematic errors in the analysis. We aim to ascertain a methodology capable of producing a consistent metallicity scale for giants and dwarfs. Methods. To achieve that, we analyzed giants and dwarfs in the Hyades open cluster, under the assumption that they share the same chemical composition. All the stars in this cluster have archival high-resolution spectroscopic data obtained with HARPS and UVES. In addition, the giants have interferometric measurements of the angular diameters. We analyzed the sample with two methods. The first method constrains the atmospheric parameters independently from spectroscopic method. For that we present a novel calibration of microturbulence based on 3D model atmospheres. The second method is the classical spectroscopic analysis based on Fe lines. We also tested two different line lists in an attempt to minimize possible non-LTE effects and to optimize the treatment of the giants. Results. We show that it is possible to obtain a consistent metallicity scale between dwarfs and giants. The preferred method should constrain the three parameters T eff , log g, and ξ independent of spectroscopy. A careful selection of Fe lines is also important. In particular, the lines should not be chosen based on the Sun or other dwarfs, but specifically to be free of blends in the spectra of giants. When attention is paid to the line list, the classical spectroscopic method can also produce consistent results. In our test, the metallicities derived with the well-constrained set of stellar parameters are consistent independent of the line list used. Therefore, for this cluster we favor the metallicity of +0.18 ± 0.03 dex obtained with this method. The classical spectroscopic analysis, using the line list optimized for the giants, provides a metallicity of +0.14 ± 0.03 dex, in agreement with previous works.

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“…In the past few years, a number of research groups have addressed the challenge of increasing the number of OC with chemical abundances determined from high-resolution spectroscopy (e.g., Sestito et al 2004;D'Orazi et al 2006;Sestito et al 2006;Bragaglia et al 2008;Pace et al 2008;Friel et al 2010;Pace et al 2010;Pancino et al 2010a;Jacobson et al 2011a). However, the number of OC with chemical abundances determined with this technique is still small (see Sect.…”

Section: Introductionmentioning

confidence: 99%

Chemical abundance analysis of the open clusters Berkeley 32, NGC 752, Hyades, and Praesepe

Carrera

Pancino

2011

A&A

128

139

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Context. Open clusters are ideal test particles for studying the chemical evolution of the Galactic disc. However, the number and accuracy of existing high-resolution abundance determinations, not only of [Fe/H], but also of other key elements, remains largely insufficient. Aims. We attempt to increase the number of Galactic open clusters that have high quality abundance determinations, and to gather all the literature determinations published so far. Methods. Using high-resolution (R ∼ 30 000), high-quality (S /N ≥ 60 per pixel), we obtained spectra for twelve stars in four open clusters with the fibre spectrograph FOCES, at the 2.2 Calar Alto Telescope in Spain. We employ a classical equivalent-width analysis to obtain accurate abundances of sixteen elements: Al, Ba, Ca, Co, Cr, Fe, La, Mg, Na, Nd, Ni, Sc, Si, Ti, V, and Y. We derived oxygen abundances by means of spectral synthesis of the 6300 Å forbidden line. Results. We provide the first determination of abundance ratios other than Fe for NGC 752 giants, and ratios in agreement with the literature for the Hyades, Praesepe, and Be 32. We use a compilation of literature data to study Galactic trends of [Fe/H] and [α/Fe] with Galactocentric radius, age, and height above the Galactic plane. We find no significant trends, but some indication for a flattening of [Fe/H] at large R gc , and for younger ages in the inner disc. We also detect a possible decrease in [Fe/H] with |z| in the outer disc, and a weak increase in [α/Fe] with R gc .

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

Cited by 25 publications

References 58 publications

Lithium abundance in the metal-poor open cluster NGC 2243

Lithium abundance in the metal-poor open cluster NGC 2243

Consistent metallicity scale for cool dwarfs and giants

Chemical abundance analysis of the open clusters Berkeley 32, NGC 752, Hyades, and Praesepe

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