Search arXiv⌕ Search
Home/Archive/arXiv

arXiv · 2610.38540

Understanding the origin of silver in metal-poor stars based on the non-local thermodynamic equilibrium analysis of Ag I lines

Lyudmila Mashonkina·Tatyana Sitnova·Svetlana A. Yakovleva·Vera A. Vasil'eva
View original source ↗Read source document ↗Export metadata ↓

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.

Explore related subjects

astro-ph.SRastro-ph.GA

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Lyudmila Mashonkina, Tatyana Sitnova, Svetlana A. Yakovleva, Vera A. Vasil'eva. 2026-10-28. Understanding the origin of silver in metal-poor stars based on the non-local thermodynamic equilibrium analysis of Ag I lines. https://arxiv.org/abs/2610.38540

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

A Low-Dimensional Chemical Representation of High-Resolution Stellar Disk Spectra: Residual Abundance Signatures

Stellar abundances are generated by complex chemical enrichment pathways yet show strong correlation structure. We test how well high-quality spectra of low-alpha disk stars can be reconstructed using low-dimensional models. By validating model performance in flux space, we quantify and locate where residual information persists. Using HARPS spectra (R = 115,000, SNR > 100) and labels derived with Korg, we train generative models (The Cannon) conditioned on stellar parameters Teff, log(g), [M/H], vsini, and vmic, and three abundance labels, [Ti/H], [Y/H], and [Nd/H], representing distinct nucleosynthetic families. Evaluating model performance on unseen test stars through flux residuals, the model reproduces the global spectra to a median residual amplitude of 0.3%. Deviations in 15 absorption features for unlabelled elements are typically < 0.7%. Residuals of ~1% correspond to abundance differences of 0.01-0.05 dex. Degrading the spectra to medium resolution (R = 28,000) decreases the median residual amplitude from 0.3% to 0.2%, redistributing the residual signal over the instrumental line profile. Our publicly available model reproduces features from 29 elements to sub-percent precision across -1.13 < [M/H] < 0.29. This demonstrates that the dominant chemical variation encoded in low-alpha disk spectra can be captured by a low-dimensional model, while weaker chemical information remains encoded in flux residuals. High-resolution, high-SNR spectra (R ~ 100,000, SNR > 100) are essential to resolve the hierarchical layers of chemical information beyond this low-dimensional structure. The model provides a benchmark for assessing the chemical information accessible to current surveys like 4MOST and GALAH 2, as well as upcoming facilities like VLT/HRMOS and GMT/G-CLEF.

astro-ph.SR↗
arXiv2026

Energy-Dependent Hard X-Ray QPP Modulation in M- and X-Class Solar Flares Observed by Aditya-L1/HEL1OS

Quasi-periodic pulsations (QPPs) in solar-flare hard X-ray (HXR) emission provide observational constraints on the temporal variability of flare energy release and energetic-electron production. In our previous study, we established a systematic catalogue of HXR QPPs in HEL1OS observations of X-class solar flares, identifying statistically significant pulsations in 25 of 34 events with sufficient data quality (S. Rajkapoor Kanaujiya et al. 2026). Here, we extend this investigation by comparing the energy dependence of the modulation depth of QPPs in M- and X-class flares across four HEL1OS energy channels spanning 8-20 keV. The comparison comprises 18 M-class events and the X-class sample from our previous study, with the number of available measurements varying between energy channels. In both flare populations, the modulation depth increases with photon energy. For M-class flares, it rises from approximately 2.3% at 8-11 keV to 13.2% at 17-20 keV, whereas for X-class flares increase from approximately 1.0% to 3.1%. The stronger increase towards higher energies in the M-class sample constitutes the principal observational contrast. These results demonstrate an energy-dependent increase in the relative amplitude of HXR QPPs in both populations and motivate a systematic statistical assessment of whether their energy-dependent modulation-depth distributions differ. The comparison provides a basis for constraining models of QPP generation and the modulation of energetic-electron emission during solar flares.

astro-ph.SR↗
arXiv2026

Recent advances in numerical modeling of solar inertial modes

Inertial modes are low-frequency global oscillations in rotating fluids, restored by the Coriolis force. Long-term observations of horizontal flows on the solar surface have led to the detection of various inertial modes on the Sun, opening a new window into the structure and dynamics of the solar interior. Here, we focus on recent advances in the theoretical modeling of solar inertial modes within a purely hydrodynamic framework, leaving magnetohydrodynamic effects beyond the scope of this review. Because the low-frequency oscillations of a differentially rotating spherical shell depend sensitively on the rotation profile and the properties of the medium, they are primarily studied using numerical models. We first summarize how linear eigenmode analyses have enabled the identification and classification of different families of inertial modes observed on the Sun, and how these models reveal the strong diagnostic potential of inertial modes for probing poorly constrained parameters in the deep convection zone, such as turbulent viscosity and superadiabaticity. The amplitudes of linearly stable modes can be estimated from their response to stochastic forcing, whereas those of linearly unstable modes must be determined using nonlinear numerical modeling. We further discuss the possible dynamical roles of large-amplitude inertial modes in transporting heat and angular momentum in the Sun. By clarifying what has been established and what remains uncertain, this review provides a framework for interpreting current observations and guiding future theoretical developments in this rapidly evolving field.

astro-ph.SR↗