The age of the Galactic thin disk from Th/Eu nucleocosmochronology

Peloso, E. F. del; Silva, L. da; Mello, G. F. Porto de

doi:10.1051/0004-6361:20047060

Cited by 26 publications

(25 citation statements)

References 51 publications

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“…The detailed description of sample selection, observations, data reduction and atmospheric parameter determination is given in del Peloso et al (2005); in what follows, we provide only a brief overview of these topics. The sample was originally selected to determine the age of the Galactic thin disk through Th/Eu nucleocosmochronology.…”

Section: Sample Selection Observations Data Reduction and Atmosphermentioning

confidence: 99%

Abundances of Mn, Co and Eu in a sample of 20 F–G disk stars: the influence of hyperfine structure splitting

Peloso¹,

Cunha²,

Silva³

et al. 2005

A&A

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We present Mn, Co and Eu abundances for a sample of 20 disk F and G dwarfs and subgiants with metallicities in the range −0.8 ≤ [Fe/H] ≤ +0.3. We investigate the influence of hyperfine structure (HFS) on the derived abundances of Mn and Co by using HFS data from different sources in the literature, as well as calculated HFS from interaction factors A and B. Eu abundances were obtained from spectral synthesis of one Eu  line that takes into account HFS from a series of recent laboratory measurements. For the lines analysed in this study, we find that for manganese, the differences between abundances obtained with different HFSs are no greater than 0.10 dex. Our cobalt abundances are even less sensitive to the choice of HFS than Mn, presenting a 0.07 dex maximum difference between determinations with different HFSs. However, the cobalt HFS data from different sources are significantly different. Our abundance results for Mn offer an independent confirmation of literature results, favouring type Ia supernovae as the main nucleosynthesis site of Mn production, in contrast to trends of Mn versus metallicity previously reported in the literature. The observed discrepancies may be attributed to the lack of HFS in the works we used for comparison. Our results for Eu are in accordance with low-mass type II supernovae being the main site of the r-process nucleosynthesis.

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Section: Sample Selection Observations Data Reduction and Atmosphermentioning

confidence: 99%

Abundances of Mn, Co and Eu in a sample of 20 F–G disk stars: the influence of hyperfine structure splitting

Peloso¹,

Cunha²,

Silva³

et al. 2005

A&A

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“…This fact is embarrassing, even in our modern era of massive surveys, since the individual study of key objects is necessary to quantify systematic errors that might be lurking inside huge databases and cannot be reduced with large number statistics. Indeed, considering only those analyses since the 90 s, eight performed a detailed analysis of the atmospheric parameters and chemical composition of α Cen A: Furenlid & Meylan (1990), hereafter FM90; Chmielewski et al (1992), Neuforge-Verheecke & Magain (1997), , hereafter ABLC04; del Peloso et al (2005a), Santos et al (2005), Valenti & Fisher (2005), and Doyle et al (2005). Five of them also performed this analysis for the cooler and fainter component α Cen B: Chmielewski et al (1992), Neuforge-Verheecke & Magain (1997), ABLC04;Valenti & Fisher (2005) and Santos et al (2005).…”

Section: Introductionmentioning

confidence: 99%

“…The papers of del Peloso et al (2005a) and Santos et al (2005) both derived a high metallicity for the system. Doyle et al (2005) added to the controversy by proposing both a low T eff and a metallicity not appreciably above solar for component A, as did FM90.…”

Section: Introductionmentioning

confidence: 99%

The Alpha Centauri binary system

Mello¹,

Lyra²,

Keller³

2008

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Context. The α Centauri binary system, owing to its duplicity, proximity and brightness, and its components' likeness to the Sun, is a fundamental calibrating object for the theory of stellar structure and evolution and the determination of stellar atmospheric parameters. This role, however, is hindered by a considerable disagreement in the published analyses of its atmospheric parameters and abundances. Aims. We report a new spectroscopic analysis of both components of the α Centauri system, compare published analyses of the system, and attempt to quantify the discrepancies still extant in the determinations of the atmospheric parameters and abundances of these stars. Methods. The analysis is differential with respect to the Sun, based on spectra with R = 35 000 and signal-to-noise ratio ≥1000, and employed spectroscopic and photometric methods to obtain as many independent T eff determinations as possible. We also check the atmospheric parameters for consistency against the results of the dynamical analysis and the positions of the components in a theoretical HR diagram. Results. The spectroscopic atmospheric parameters of the system are found to be T eff = (5847 ± 27) K, [Fe/H] = +0.24 ± 0.03, log g = 4.34 ± 0.12, and ξ t = 1.46 ± 0.03 km s −1 , for α Cen A, and T eff = (5316 ± 28) K, [Fe/H] = +0.25 ± 0.04, log g = 4.44 ± 0.15, and ξ t = 1.28 ± 0.15 km s −1 for α Cen B. The parameters were derived from the simultaneous excitation & ionization equilibria of Fe I and Fe II lines. T eff s were also obtained by fitting theoretical profiles to the Hα line and from photometric calibrations. Conclusions. We reached good agreement between the three criteria for α Cen A. For α Cen B the spectroscopic T eff is ∼140 K higher than the other two determinations. We discuss possible origins of this inconsistency, concluding that the presence of non-local thermodynamic equilibrium effects is a probable candidate, but we note that there is as yet no consensus on the existence and cause of an offset between the spectroscopic and photometric T eff scales of cool dwarfs. The spectroscopic surface gravities also agree with those derived from directly measured masses and radii. An average of three independent T eff criteria leads to T eff (A) = (5824 ± 26) K and T eff (B) = (5223 ± 62) K. The abundances of Na, Mg, Si, Mn, Co, and Ni and, possibly, Cu are significantly enriched in the system, which also seems to be deficient in Y and Ba. This abundance pattern can be deemed normal in the context of recent data on metal-rich stars. The position of α Cen A in an up-to-date theoretical evolutionary diagram yields a good match of the evolutionary mass and age (in the 4.5 to 5.3 Gyr range) with those from the dynamical solution and seismology, but only marginal agreement for α Cen B, taking into account its more uncertain T eff .

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“…An interesting conflict appears for ζ 1 Ret. Del Peloso et al (2000) suggest that these stars show a higher chromospheric flux than expected for its age. A possible solution to this problem may be the analysis of the chromospheric flux of ζ 1 Ret through other chromospheric indicators, along with the other solar-type group members.…”

Section: Discussionmentioning

confidence: 86%

“…The rarity of old kinematic groups bears witness to the processes that tear them apart, probably encounters with massive objects, such spiral arms and molecular clouds, in time scales of a billion years or less. Therefore, the majority of these groups must be young but some relatively old groups have already been considered as is the case of the Zeta Reticuli group (del Peloso et al 2000).…”

Section: Introductionmentioning

confidence: 99%

On The Physical Existence of The Zeta Reticuli Moving Group: A Chemical Composition Analysis

2009

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Abstract.We report the spectroscopic analysis of six kinematical members of the Zeta Reticuli Moving Group, one of them for the first time. We confirm the existence of the Group by establishing a common abundance pattern for four kinematical members. High resolution spectra yielded abundances of Si, Ca, Fe, Ni and Ba, and others. Effective temperatures were derived from the excitation & ionization equilibria of Fe lines of four stars. For these, and the remaining two members, temperatures were derived from colors and the fitting of theoretical spectra to the Hα line, and ages and masses were estimated from theoretical HR diagrams. We suggest that the Group is physical being metal-poor and ∼6 Gyr old.

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The age of the Galactic thin disk from Th/Eu nucleocosmochronology

Cited by 26 publications

References 51 publications

Abundances of Mn, Co and Eu in a sample of 20 F–G disk stars: the influence of hyperfine structure splitting

Abundances of Mn, Co and Eu in a sample of 20 F–G disk stars: the influence of hyperfine structure splitting

The Alpha Centauri binary system

On The Physical Existence of The Zeta Reticuli Moving Group: A Chemical Composition Analysis

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