Looking for imprints of the first stellar generations in metal-poor bulge field stars

TL;DR

This study investigates metal-poor bulge stars for signatures of the first stellar generations by analyzing high-resolution spectra to derive detailed elemental abundances, aiming to identify imprints of the earliest stars in the Milky Way.

Contribution

It provides high-resolution spectroscopic analysis of bulge stars with low metallicity and alpha-enhancement, revealing detailed elemental abundances relevant to early stellar populations.

Findings

Derived stellar parameters and elemental ratios for five bulge stars.

Identified abundance patterns that may indicate signatures of the first stellar generations.

Enhanced understanding of the chemical composition of ancient bulge stars.

Abstract

Context. Efforts to look for signatures of the first stars have concentrated on metal-poor halo objects. However, the low end of the bulge metallicity distribution has been shown to host some of the oldest objects in the Milky Way and hence this Galactic component potentially offers interesting targets to look at imprints of the first stellar generations. As a pilot project, we selected bulge field stars already identified in the ARGOS survey as having [Fe/H] ~ -1 and oversolar [alpha/Fe] ratios, and we used FLAMES-UVES to obtain detailed abundances of key elements that are believed to reveal imprints of the first stellar generations. Aims. The main purpose of this study is to analyse selected ARGOS stars using new high-resolution (R~45,000) and high-signal-to-noise (S/N >100) spectra. We aim to derive their stellar parameters and elemental ratios, in particular the abundances of C, N, the alpha-elements O, Mg, Si, Ca, and Ti, the odd-Z elements Na and Al, the neutron-capture s-process dominated elements Y, Zr, La, and Ba, and the r-element Eu. Methods. High-resolution spectra of five field giant stars were obtained at the 8m VLT UT2-Kueyen telescope with the UVES spectrograph in FLAMES-UVES configuration. Spectroscopic parameters were derived based on the excitation and ionization equilibrium of Fe I and Fe II. The abundance analysis was performed with a MARCS LTE spherical model atmosphere grid and the Turbospectrum spectrum synthesis code.