Barium and yttrium abundance in intermediate-age and old open clusters★

Коротин, С. А.; Carraro, G.; Kovtyukh, V. V.; Yegorova, I.

doi:10.1093/mnras/stt818

Cited by 37 publications

(57 citation statements)

References 48 publications

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“…The second issue is strongly related to the rate of the 13 C(α, n) 16 O reaction, which is diffusely discussed in [10,11]. Entering into the details of its measurements is not the aims of this work.…”

Section: The 13 C-pocket Formationmentioning

confidence: 99%

“…The 13 C(α, n) 16 O is activated during the radiative phase between two subsequent TPs; the 22 Ne(α,-n) 25 Mg is instead at play inside the convective instabilities. Due to its need for high temperatures, it is only marginally activated in LMS where, even in the pulses, T < 3 × 10 8 K. The neutron density, induced by the above reactions (about 10 6 −10 10 n/cm 3 ), is typical of slow neutron capture nucleosynthesis, i.e.…”

Section: The S-process In Agb-lmsmentioning

confidence: 99%

“…The 13 C(α, n) 16 O reaction, originally introduced by [4], is the main neutron source for producing the s-nuclei from strontium to bismuth in LMS. It usually takes place at relatively low temperatures (T = 0.8 − 1.0 × 10 8 K) providing a neutron density of the order of 10 6 − 10 7 n/cm 3 .…”

Section: The 13 C-pocket Formationmentioning

confidence: 99%

“…In order to activate the 13 C(α, n) 16 O reaction, two conditions must be met: i) a mechanism for injecting protons into the He-rich region must be found, so that interacting with the abundant 12 C they can produce 13 C in the He intershell; ii) the amount of 13 C thus obtained must burn through the 13 C(α, n) 16 O reaction in layers where the temperature is low, to maintain the neutron density low.…”

Section: The 13 C-pocket Formationmentioning

confidence: 99%

“…

…”

mentioning

confidence: 99%

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Does the main component of the s-process in AGB stars constrain the neutron source in the 13C-pocket?

Trippella¹

2015

Proceedings of XIII Nuclei in the Cosmos — PoS(NIC XIII)

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The 13 C(α, n) 16 O reaction is considered as the main responsible for the production of the sprocess main component in low-mass AGB stars. Its activation requires a physical mechanism to ingest protons in the He-rich region forming a 13 C reservoir, or pocket. This was typically assumed to involve a small mass (≤ 10 −3 M ) [7], but recent observations in several astrophysical sites showed enhancements of s-element abundances with respect to the Sun suggesting a more effective s-process nucleosynthesis. This requires a more extended 13 C pocket covering, in mass (≥ 4 × 10 −3 M ), most of the He-rich layers. Recently, we suggested that magnetic buoyancy could promote forced mixing [14,20] to produce a 13 C reservoir larger than assumed so far. Here we investigate if the solar composition of neutron rich elements, from Sr to Bi, can constrain the 13 C-pocket extension. Stellar models at a fixed metallicity, based on a large 13 C reservoir reproduce the distribution of s-only elements within the uncertainty of 10%, also fulfilling C-star luminosity observations. Assuming this new scenario, a large production of nuclei below A = 90 is expected, so that 86, 87 Sr may be fully synthesized by AGB stars, while 88 Sr, 89 Y and 94 Zr are contributed more efficiently than before.

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Section: The 13 C-pocket Formationmentioning

confidence: 99%

Section: The S-process In Agb-lmsmentioning

confidence: 99%

Section: The 13 C-pocket Formationmentioning

confidence: 99%

Section: The 13 C-pocket Formationmentioning

confidence: 99%

“…

…”

mentioning

confidence: 99%

See 3 more Smart Citations

Does the main component of the s-process in AGB stars constrain the neutron source in the 13C-pocket?

Trippella¹

2015

Proceedings of XIII Nuclei in the Cosmos — PoS(NIC XIII)

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s-Processing from MHD-induced mixing and isotopic abundances in presolar SiC grains

Palmerini

Trippella

Busso

et al. 2018

Geochimica et Cosmochimica Acta

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In the past years the observational evidence that s-process elements from Sr to Pb are produced by stars ascending the socalled Asymptotic Giant Branch (or ''AGB") could not be explained by self-consistent models, forcing researchers to extensive parameterizations. The crucial point is to understand how protons can be injected from the envelope into the He-rich layers, yielding the formation of 13 C and then the activation of the 13 Cða; nÞ 16 O reaction. Only recently, attempts to solve this problem started to consider quantitatively physically-based mixing mechanisms. Among them, MHD processes in the plasma were suggested to yield mass transport through magnetic buoyancy. In this framework, we compare results of nucleosynthesis models for Low Mass AGB Stars (M K 3M ), developed from the MHD scenario, with the record of isotopic abundance ratios of s-elements in presolar SiC grains, which were shown to offer precise constraints on the 13 C reservoir. We find that n-captures driven by magnetically-induced mixing can indeed account for the SiC data quite well and that this is due to the fact that our 13 C distribution fulfils the above constraints rather accurately. We suggest that similar tests should be now performed using different physical models for mixing. Such comparisons would indeed improve decisively our understanding of the formation of the neutron source.

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Chemical abundance analysis of the old, rich open cluster Trumpler 20

Carraro¹,

Villanova

Monaco³

et al. 2014

A&A

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Aims. Trumpler 20 is an open cluster located at low Galactic longitude, just beyond the great Carina spiral arm, and whose metallicity and fundamental parameters were very poorly known until now. As it is most likely a rare example of an old, rich open clusterpossibly a twin of NGC 7789 -it is useful to characterize it. To this end, we determine here the abundance of several elements and their ratios in a sample of stars in the clump of Trumpler 20. Methods. We present high-resolution spectroscopy of eight clump stars. Based on their radial velocities, we identify six bona fide cluster members, and for five of them (the sixth being a fast rotator) we perform a detailed abundance analysis. Results. We find that Trumpler 20 is slightly more metal-rich than the Sun, having [Fe/H] = +0.09 ± 0.10. The abundance ratios of α-elements are generally solar. In line with recent studies of clusters as old as Trumpler 20, Ba is overabundant compared to the Sun. Our analysis of the iron-peak elements (Cr and Ni) does not reveal anything anomalous. Based on these results, we re-estimate the cluster age to be 1.5 +0.2 −0.1 Gyr. Its distance to the Galactic centre turns out to be 7.3 kpc. With this distance and metallicity, Trumpler 20 fits fairly well in the metallicity gradient for the Galactic inner disc. Conclusions. With this new study, the characterization of Trumpler 20 is now on much more solid ground. Further studies should focus on the estimate of the binary fraction and on its main sequence membership.

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Barium and yttrium abundance in intermediate-age and old open clusters★

Cited by 37 publications

References 48 publications

Does the main component of the s-process in AGB stars constrain the neutron source in the 13C-pocket?

Does the main component of the s-process in AGB stars constrain the neutron source in the 13C-pocket?

s-Processing from MHD-induced mixing and isotopic abundances in presolar SiC grains

Chemical abundance analysis of the old, rich open cluster Trumpler 20

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