arXiv subjects

Tamara Mishenina

Publications and source records attributed to Tamara Mishenina.

3 recordsLinked to original sources

arXiv2026

Stellar Population Astrophysics (SPA) with the TNG. Beyond the iron peak: Galactic evolution of molybdenum, ruthenium and zirconium through open clusters

Context: Open clusters serve as key laboratories for studying the chemical evolution of the Milky Way. In particular, leveraging these coeval groups of stars to study elements beyond the iron peak provides insights into heavy-element nucleosynthesis, whose origins remain uncertain. Aims: This work aims to determine the Mo, Ru, and Zr abundances for 81 stars across 30 open clusters. We compare these new chemical patterns with those of key reference elements (Y, Sr, Eu), which were previously derived by our group. This comparison seeks to disentangle the distinct contributions from various nucleosynthetic processes. Methods: Using the high-resolution spectra acquired within the Stellar Population Astrophysics programme using the HARPS-N echelle spectrograph at the Telescopio Nazionale Galileo, we estimate chemical abundances through spectral synthesis with TSFitPy under local thermodynamic equilibrium (LTE) conditions. Results: This study provides the first Ru abundances for a large open cluster sample, alongside new measurements for Mo and Zr. We observe tight correlations between Mo, Ru, and other s-process elements (Sr, Y, Zr), with slopes near unity, suggesting common enrichment timescales. Conversely, relations with the r-process element Eu show significant deviations, implying additional nucleosynthetic contributions. Crucially, chemical planes involving [Mo/Ru] and [s/Mo] ratios suggest systematic offsets when compared to theoretical s-process predictions.

astro-ph.GA↗

arXiv2025

Molybdenum and ruthenium in the Galactic disk: A closer look at their nucleosynthesis components

The stellar origin of the elements molybdenum (Mo, Z=42) and ruthenium (Ru, Z=44) is still a matter of debate. Studying their abundances provides valuable insights into nucleosynthesis processes and the broader evolution of neutron-capture elements. We presented new observations of Mo and Ru, together with nearby neutron-capture elements strontium (Sr) and zirconium (Zr) for a new sample of 154 giant stars, located in the Galactic disk with metallicities -1 < [Fe/H] < +0.3. The abundances were determined under the assumption of the local thermodynamic equilibrium by fitting synthetic spectra. The abundances of Mo were derived from the Mo I lines at 5506 and 5533 A, the abundances of Ru were determined from Ru I lines at 4584, and 4757 A. For most of the giant stars observed in this work, Mo and Ru abundances were determined for the first time. We compare our observations with the signatures from different nucleosynthesis processes. Both the [Mo/Fe] and [Ru/Fe] in our stars show a decreasing trend with respect to increasing [Fe/H]. This pattern is similar to that of [Zr/Fe], whereas [Sr/Fe] exhibits a relatively flat trend with metallicity. Compared to the s-process ratios, all stars show a lower [Zr/Mo] and a higher [Ru/Mo], as expected from classical nucleosynthesis. Still, it is unclear if additional contributions from neutrino-wind components or the i-process is needed to explain the observed scatter of [Zr/Mo] and [Ru/Mo] in the Milky Way disk. Indeed, such a dispersion is consistent with the variations also seen in r-II stars at low metallicity and could therefore result from the combined contributions of r-process and s-process to galactic chemical evolution. The observed [Zr/Mo] and [Ru/Mo] scatter in r-II stars should be constrained by future investigations to define if any contributions of additional nucleosynthesis components are needed.

astro-ph.GA↗

arXiv2019

Enrichment of the Galactic disc with neutron-capture elements: Mo and Ru

We present new observational data for the heavy elements molybdenum (Mo, Z = 42) and ruthenium (Ru, Z = 44) in F-, G-, and K-stars belonging to different substructures of the Milky Way. The range of metallicity covered is --1.0 $<$ [Fe/H] $<$ +0.3. The spectra of Galactic disc stars have a high resolution of 42,000 and 75,000 and signal-to-noise ratio better than 100. Mo and Ru abundances were derived by comparing the observed and synthetic spectra in the region of Mo I lines at 5506, 5533 Å~ for 209 stars and Ru I lines at 4080, 4584, 4757 Å~ for 162 stars using the LTE approach. For all the stars, the Mo and Ru abundance determinations are obtained for the first time with an average error of 0.14 dex. This is the first extended sample of stellar observations for Mo and Ru in the Milky Way disc, and together with earlier observations in halo stars it is pivotal in providing a complete picture of the evolution of Mo and Ru across cosmic timescales. The Mo and Ru abundances were compared with those of the neutron-capture elements (Sr, Y, Zr, Ba, Sm, Eu). The complex nucleosynthesis history of Mo and Ru is compared with different Galactic Chemical Evolution (GCE) simulations. In general, present theoretical GCE simulations show underproduction of Mo and Ru at all metallicities compared to observations. This highlights a significant contribution of nucleosynthesis processes not yet considered in our simulations. A number of possible scenarios are discussed.

astro-ph.GA↗