# Enrichment of the Galactic disc with neutron capture elements: Sr

## TL;DR

This study provides new observational data on strontium (Sr) in 276 Galactic disc stars, analyzing its abundance and nucleosynthesis origins to enhance understanding of the Galaxy's chemical evolution.

## Contribution

It offers the first extensive Sr abundance measurements in Galactic disc stars, comparing LTE and NLTE corrections, and discusses nucleosynthesis sources in the context of Galactic chemical evolution models.

## Key findings

- Sr abundance increases with metallicity.
- NLTE corrections are minor near solar metallicity.
- s-process from AGB and massive stars are main Sr sources.

## Abstract

The enrichment history of heavy neutron-capture elements in the Milky Way disc provides fundamental information about the chemical evolution of our Galaxy and about the stellar sources that made those elements. In this work we give new observational data for Sr, the element at the first neutron-shell closure beyond iron, N=50, based on the analysis of the high resolution spectra of 276 Galactic disc stars. The Sr abundance was derived by comparing the observed and synthetic spectra in the region of the SrI 4607 A line, making use of the LTE approximation. NLTE corrections lead to an increase of the abundance estimates obtained under LTE, but for these lines they are minor near solar metallicity. The average correction that we find is 0.151 dex. The star that is mostly affected is HD 6582, with a 0.244 dex correction. The behavior of the Sr abundance as a function of metallicity is discussed within a stellar nucleosynthesis context, in comparison with the abundance of the heavy neutron-capture elements Ba (Z=56) and Eu (Z=63). The comparison of the observational data with the current GCE models confirm that the s-process contributions from Asymptotic Giant Branch stars and from massive stars are the main sources of Sr in the Galactic disc and in the Sun, while different nucleosynthesis sources can explain the high [Sr/Ba] and [Sr/Eu] ratios observed in the early Galaxy.