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arXiv · 2302.10504

Ba-enhanced dwarf and subgiant stars in the LAMOST Galactic surveys

Meng Zhang·Maosheng Xiang·Hua-Wei Zhang·Yuan-Sen Ting·Ya-Qian Wu·Xiao-Wei Liu
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Abstract

Ba-enhanced stars are interesting probes of stellar astrophysics and Galactic formation history. In this work, we investigate the chemistry and kinematics for a large sample of Ba-enhanced ([Ba/Fe]$>$1.0) dwarf and subgiant stars with $5000 < T_{\rm eff }< 6700$\,K from LAMOST. We find that both stellar internal evolution process and external mass exchange due to binary evolution are responsible for the origins of the Ba-enhancement of our sample stars. About one third of them exhibit C and N enhancement and ultraviolet brightness excess, indicating they are products of binary evolution. The remaining Ba-enhanced stars with normal C and N abundances are mostly warm stars with $T_{\rm eff} > 6000$\,K. They are likely consequences of stellar internal elemental transport processes, but they show very different elemental patterns to the hotter Am/Fm stars. Our results reveal a substantially lack of high-[$\alpha$/Fe] Ba-enhanced stars in the [Fe/H]--[$\alpha$/Fe] plane, which we dub as a {\em high-$\alpha$ desert}. We suggest it is due to a lower efficiency for producing Ba-enhanced stars by low-mass AGB progenitors in binary systems. Our results call for detailed modellings for these Ba-enhanced stellar peculiars, in the context of both stellar internal elemental transport and external mass accretion.

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Meng Zhang, Maosheng Xiang, Hua-Wei Zhang, Yuan-Sen Ting, Ya-Qian Wu, Xiao-Wei Liu. 2023-02-21. Ba-enhanced dwarf and subgiant stars in the LAMOST Galactic surveys. https://doi.org/10.3847/1538-4357%2Facbcc4

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