The Barium Isotopic Abundance in the Metal-Poor Star HD140283

TL;DR

This study measures the barium isotopic composition in the metal-poor star HD140283 using high-resolution spectroscopy, revealing insights into neutron-capture processes in early stellar environments.

Contribution

It provides the first detailed isotopic analysis of barium in HD140283 using both 1D and 3D models, highlighting the importance of 3D modeling for accurate results.

Findings

1D analysis suggests a 64% r-process contribution.

3D analysis indicates a 15% r-process contribution.

Results are consistent with a solar-like isotopic mixture.

Abstract

We derive the mixture of odd to even barium isotopes in the atmosphere of the metal-poor subgiant HD140283 from the analysis of the Ba II transition at 455.4 nm in a high-resolution high signal-to-noise spectrum of the star. The detailed shape of this spectral line depends on the relative contributions of odd and even isotopes via isotopic and hyperfine splitting. We measure the fractional abundance of odd Ba isotopes by modelling the formation of the Ba II 455.4 nm line profile with the use of both a classical 1D hydrostatic and a 3D hydrodynamical model atmosphere of HD140283. We interpret the results in terms of contributions by the slow (s-) and rapid (r-) neutron-capture processes to the isotopic mix. While the result of the 1D analysis of the Ba II feature indicates a (64 +/- 36)% contribution of the r-process to the isotopic mix, the 3D analysis points toward a mere (15 +/- 34)% contribution from this process, that is consistent with a solar-like mixture of barium isotopes.