Ba Enrichment in Gaia MS+WD Binaries: Tracing $s$-Process Element Production

Abstract

A large population of intermediate-separation binaries, consisting of a main-sequence (MS) star and a white dwarf (WD), has recently emerged from Gaia's third data release (DR3), posing challenges to current models of binary evolution. Here we examine the $s$-process element abundances in these systems using data from GALAH DR3. Following refined sample analysis with parameter estimates based on GALAH spectra, we find a distinct locus where enhanced $s$-process elements depend on both the WD mass and metallicity, consistent with loci identified in previous asymptotic giant branch (AGB) nucleosynthesis studies with higher $s$-process yields. Notably, these enhanced abundances show no correlation with the systems' orbital parameters, supporting a history of accretion in intermediate-separation MS+WD systems. Consequently, our results form a direct observational evidence of a connection between AGB masses and $s$-process yields. We conclude by showing that the GALAH DR3 survey includes numerous Ba dwarf stars, within and beyond the mass range covered in our current sample, which can further elucidate $s$-process element distributions in MS+WD binaries.

Published in ApJL; 12 pages, 10 figures

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