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arXiv · 2104.04265

Chemical Tagging N-rich Field Stars with High-resolution Spectroscopy

Jincheng Yu·Baitian Tang·J. G. Fernandez-Trincado·Douglas Geisler·Hongliang Yan·M. Soto
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Abstract

We measure chemical abundances for over 20 elements of 15 N-rich field stars with high resolution ($R \sim 30000$) optical spectra. We find that Na, Mg, Al, Si, and Ca abundances of our N-rich field stars are mostly consistent with those of stars from globular clusters (GCs). Seven stars are estimated to have [Al/Fe$]>0.5$, which is not found in most GC "first generation" stars. On the other hand, $\alpha$ element abundances (especially Ti) could show distinguishable differences between in situ stars and accreted stars. We discover that one interesting star, with consistently low [Mg/Fe], [Si/Fe], [Ca/Fe], [Ti/Fe], [Sc/Fe], [V/Fe], and [Co/Fe], show similar kinematic and [Ba/Eu] as other stars from the dissolved dwarf galaxy "$Gaia$-Sausage-Enceladus". The $\alpha$-element abundances and the iron-peak element abundances of the N-rich field stars with metallicities $-1.25 \le {\rm [Fe/H]} \le -0.95$ show consistent values with Milky Way field stars rather than stars from dwarf galaxies, indicating that they were formed in situ. In addition, the neutron capture elements of N-rich field stars show that most of them could be enriched by asymptotic giant branch (AGB) stars with masses around $3 - 5\, M_{\odot}$.

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Jincheng Yu, Baitian Tang, J. G. Fernandez-Trincado, Douglas Geisler, Hongliang Yan, M. Soto. 2021-04-09. Chemical Tagging N-rich Field Stars with High-resolution Spectroscopy. https://doi.org/10.3847/1538-4357%2Fabf64d

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