Understanding the origin of silver in metal-poor stars based on the non-local thermodynamic equilibrium analysis of Ag I lines
Abstract
Silver is a poorly observed neutron-capture element, and understanding its Galactic production history requires accurate abundances for stellar samples covering a broad metallicity range. We refined the method for calculating stellar Ag abundances by considering the non-local thermodynamic equilibrium (NLTE) line formation for Ag I. A comprehensive model atom of silver was built from the atomic data available in the literature, including recent data on inelastic Ag I + H I collisions. We derived abundances using the high-resolution spectra and the synthetic spectrum method with the one-dimensional model atmospheres. From two Ag I lines in the solar spectrum we obtained the NLTE abundances log epsilon = 1.15 and 1.10 for different treatments of collisions with hydrogen atoms. The NLTE abundances of Ag were determined for the first time for 41 stars in the -2.74 <= [Fe/H] <= -0.56 metallicity range. The NLTE abundance corrections for Ag I 3382 A were found to be larger for the giants (up to 0.92~dex) than the dwarfs (up to 0.51~dex). In NLTE, Ag in our sample stars is enhanced relatively to Fe and the [Ag/Fe] Galactic trend is very similar to that for [Eu/Fe]; the [Ag/Eu], [Ag/Ba], and [Ag/Sr] abundance ratios of the r-II stars CS22892-052 and CS31082-001 agree very well with the r-process model of Prantzos et al. (2020); the -1.6 < [Fe/H] <= -0.56 stars have close-to-solar [Ag/Eu] ratios. We conclude that production of silver was dominated by the main r-process throughout the metallicity range we investigated, with the main s-process contribution of not larger than 20% for [Fe/H] > -1.6.
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BibTeX
@misc{mashonkina2026understanding,
title = {{Understanding the origin of silver in metal-poor stars based on the non-local thermodynamic equilibrium analysis of Ag I lines}},
author = {Lyudmila Mashonkina and Tatyana Sitnova and Svetlana A. Yakovleva and Vera A. Vasil'eva},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.38540},
eprint = {2610.38540},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.38540},
}
RIS
TY - UNPB
TI - Understanding the origin of silver in metal-poor stars based on the non-local thermodynamic equilibrium analysis of Ag I lines
AU - Lyudmila Mashonkina
AU - Tatyana Sitnova
AU - Svetlana A. Yakovleva
AU - Vera A. Vasil'eva
PY - 2026
DA - 2026/10/28
PB - arXiv
DO - 10.48550/arxiv.2610.38540
UR - https://arxiv.org/abs/2610.38540
AB - Silver is a poorly observed neutron-capture element, and understanding its Galactic production history requires accurate abundances for stellar samples covering a broad metallicity range. We refined the method for calculating stellar Ag abundances by considering the non-local thermodynamic equilibrium (NLTE) line formation for Ag I. A comprehensive model atom of silver was built from the atomic data available in the literature, including recent data on inelastic Ag I + H I collisions. We derived abundances using the high-resolution spectra and the synthetic spectrum method with the one-dimensional model atmospheres. From two Ag I lines in the solar spectrum we obtained the NLTE abundances log epsilon = 1.15 and 1.10 for different treatments of collisions with hydrogen atoms. The NLTE abundances of Ag were determined for the first time for 41 stars in the -2.74 <= [Fe/H] <= -0.56 metallicity range. The NLTE abundance corrections for Ag I 3382 A were found to be larger for the giants (up to 0.92~dex) than the dwarfs (up to 0.51~dex). In NLTE, Ag in our sample stars is enhanced relatively to Fe and the [Ag/Fe] Galactic trend is very similar to that for [Eu/Fe]; the [Ag/Eu], [Ag/Ba], and [Ag/Sr] abundance ratios of the r-II stars CS22892-052 and CS31082-001 agree very well with the r-process model of Prantzos et al. (2020); the -1.6 < [Fe/H] <= -0.56 stars have close-to-solar [Ag/Eu] ratios. We conclude that production of silver was dominated by the main r-process throughout the metallicity range we investigated, with the main s-process contribution of not larger than 20% for [Fe/H] > -1.6.
ER -