Comprehensive abundance analysis of red giants in the open clusters NGC 2527, 2682, 2482, 2539, 2335, 2251 and 2266

Reddy, Arumalla B. S.; Giridhar, Sunetra; Lambert, David L.

doi:10.1093/mnras/stt412

Cited by 57 publications

(70 citation statements)

References 37 publications

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“…Table 8 summarizes the compositions of the local asso- Table 8. Mean elemental abundance ratios, [X/Fe], for Na to Eu for our sample of five associations, the thin disc mean abundances from Reddy et al (2012Reddy et al ( & 2013 and Reddy et al (2015) for OC giants, and Luck & Heiter (2007) for field giants, and Luck & Heiter (2005 and Bensby et al (2014) for field dwarfs, and Luck & Lambert (2011) ciations and the comparison samples mentioned above. Entries for the field dwarfs are taken from Luck & Heiter (2005 and from Benbsy et al (2014) with the constraint that [Fe/H] is in the range −0.10 to +0.10.…”

Section: Associations Clusters and Field Starsmentioning

confidence: 99%

“…Over the last few years, several comprehensive highresolution studies of chemical abundances in the solar vicinity have been reported for field dwarfs (Edvardsson et al 1993;Reddy et al 2003Reddy et al , 2006Luck & Heiter 2005Bensby et al 2005Bensby et al , 2014, field giants (Mishenina et al 2006;Luck & Heiter 2007;Takeda et al 2008), and for open clusters (OCs; Friel et al 2002;Bragaglia et al 2008;Yong et al 2012;Reddy et al 2013Reddy et al , 2015, with the main goal of improving our knowledge of the chemical evolution of the Galactic disc.…”

Section: Introductionmentioning

confidence: 99%

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Local associations and the barium puzzle

Reddy

Lambert

2015

Mon. Not. R. Astron. Soc.

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We have observed high-dispersion echelle spectra of main-sequence stars in five nearby young associations -Argus, Carina-Near, Hercules-Lyra, Orion and Subgroup B4 -and derived abundances for elements ranging from Na to Eu. These are the first chemical abundance measurements for two of the five associations, while the remaining three associations are analysed more extensively in our study. Our results support the presence of chemical homogeneity among association members with a typical starto-star abundance scatter of about 0.06 dex or less over many elements. The five associations show log ǫ(Li) consistent with their age and share a solar chemical composition for all elements with the exception of Ba. We find that all the heavy elements (Y, Zr, La, Ce, Nd, Sm and Eu) exhibit solar ratios, i.e., [X/Fe] ≃ 0, while Ba is overabundant by about 0.2−0.3 dex. The origin of the overabundance of Ba is a puzzle. Within the formulation of the s-process, it is difficult to create a higher Ba abundance without a similar increase in the s-process contributions to other heavy elements (LaSm). Given that Ba is represented by strong lines of Ba ii and La-Sm are represented by rather weak ionized lines, the suggestion, as previously made by other studies, is that the Ba abundance may be systematically overestimated by standard methods of abundance analysis perhaps because the upper reaches of the stellar atmospheres are poorly represented by standard model atmospheres. A novel attempt to analyse the Ba i line at 5535Å gives a solar Ba abundance for stars with effective temperatures hotter than about 5800 K but increasingly subsolar Ba abundances for cooler stars with apparent Ba deficiencies of 0.5 dex at 5100 K. This trend with temperature may signal a serious non-LTE effect on the Ba i line.

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Section: Associations Clusters and Field Starsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Local associations and the barium puzzle

Reddy

Lambert

2015

Mon. Not. R. Astron. Soc.

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“…The ages were calculated consistently, according to Carraro & Chiosi (1994). In the figures we include abundances obtained earlier (Mishenina et al 2013b(Mishenina et al , 2014 with measurements from other authors, for a number of OCs (D' Orazi et al 2009;Pancino et al 2010;Carrera & Pancino 2011;Maiorca et al 2011;D' Orazi et al 2012;Reddy et al 2012Reddy et al , 2013Bragaglia et al 2008;Yong et al 2005;Jacobson & Friel 2013) and the data for the thin disk stars were taken from the study by Mishenina et al (2013a).…”

Section: Etc) More In Generalmentioning

confidence: 99%

New insights on Ba overabundance in open clusters.★ Evidence for the intermediate neutron-capture process at play?

Mishenina

Pignatari

Carraro

et al. 2014

Monthly Notices of the Royal Astronomical Society

111

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Recently an increasing number of studies were devoted to measure the abundances of neutron-capture elements heavier than iron in stars belonging to Galactic Open Clusters (OCs). OCs span a sizeable range in metallicity (-0.6 ≤ [Fe/H] ≤ +0.4), and they show abundances of light elements similar to disk stars of the same age. A different pattern is observed for heavy elements. A large scatter is observed for Ba, with most OCs showing [Ba/Fe] and [Ba/La] overabundant with respect to the Sun. The origin of this overabundance is not clearly understood. With the goal of providing new observational insights we determined radial velocities, atmospheric parameters and chemical composition of 27 giant stars members of five OCs: Cr 110, Cr 261, NGC 2477, NGC 2506 and NGC 5822. We used high-resolution spectra obtained with the UVES spectrograph at ESO Paranal. We perform a detailed spectroscopic analysis of these stars to measure the abundance of up to 22 elements per star. We study the dependence of element abundance on metallicity and age with unprecedented detail, complementing our analysis with data culled from the literature. We confirm the trend of Ba overabundance in OCs, and show its large dispersion for clusters younger than ∼4 Gyr. Finally, the implications of our results for stellar nucleosynthesis are discussed. We show in this work that the Ba enrichment compared to other neutron-capture elements in OCs cannot be explained by the contributions from the slow neutroncapture process and the rapid neutron-capture process. Instead, we argue that this anomalous signature can be explained by assuming an additional contribution by the intermediate neutron-capture process.

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“…The sample red giant star HD 16771 analysed in this letter was selected as a part of the program dedicated to measure chemical abundances for red giants in open clusters (OCs; Reddy et al 2012Reddy et al , 2013Reddy et al , 2015. High-resolution (R ∼ 60 000) and high signal-to-noise ratio (S/N) optical spectra of HD 16771 were acquired during the night of 2013 November with the A&A 589, A57 (2016) Robert G. Tull coudé cross-dispersed echelle spectrograph (Tull et al 1995) at the 2.7-m Harlan J. Smith reflector of the McDonald observatory.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

HD 16771: A lithium-rich giant in the red-clump stage

Reddy

Lambert

2016

A&A

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Aims. We report the discovery of a young lithium rich giant, HD 16771, in the core-helium burning phase that does not seem to fit existing proposals of Li synthesis near the luminosity function bump or during He-core flash. We aim to understand the nature of Li enrichment in the atmosphere of HD 16771 by exploring various Li enhancement scenarios. Methods. We have collected high-resolution echelle spectra of HD 16771 and derived stellar parameters and chemical abundances for 27 elements by either line equivalent widths or synthetic spectrum analyses. Results. HD 16771 is a Li-rich (log (Li) = +2.67 ± 0.10 dex) intermediate mass giant star (M = 2.4 ± 0.1 M ) with age ∼ 0.76 ± 0.13 Gyr and located at the red giant clump. Kinematics and chemical compositions are consistent with HD 16771 being a member of the Galactic thin disk population. The non-detection of 6 Li (<3%), a low carbon isotopic ratio ( 12 C/ 13 C = 12 ± 2), and the slow rotation (v sin i = 2.8 km s −1 ) all suggest that lithium might have been synthesized in this star. On the contrary, HD 16771 with a mass of 2.4 M has no chance of encountering luminosity function bump and He-core flash where the possibility of fast deep-mixing for Li enrichment in K giants has been suggested previously. Conclusions. Based of the evolutionary status of this star, we discuss the possibility that 7 Li synthesis in HD 16771 is triggered by the engulfment of close-in planet(s) during the RGB phase.

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Comprehensive abundance analysis of red giants in the open clusters NGC 2527, 2682, 2482, 2539, 2335, 2251 and 2266

Cited by 57 publications

References 37 publications

Local associations and the barium puzzle

Local associations and the barium puzzle

New insights on Ba overabundance in open clusters.★ Evidence for the intermediate neutron-capture process at play?

HD 16771: A lithium-rich giant in the red-clump stage

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