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We identified 8 additional stars as members of the Helmi stream (HStr) in the combined GALAH+ DR3 and $Gaia$ EDR3 catalog. By consistently reevaluating claimed members from the literature, we consolidate a sample of 22 HStr stars with parameters determined from high-resolution spectroscopy and spanning a considerably wider (by $sim$0.5 dex) metallicity interval ($-2.5 lesssim rm[Fe/H] < -1.0$) than previously reported. Our study focuses on $alpha$ (Mg and Ca) and neutron-capture (Ba and Eu) elements. We find that the chemistry of HStr is typical of dwarf spheroidal (dSph) galaxies, in good agreement with previous $N$-body simulations of this merging event. Stars of HStr constitute a clear declining sequence in $rm[alpha/Fe]$ for increasing metallicity up to $rm[Fe/H] sim -1.0$. Moreover, stars of HStr show a median value of $+$0.5 dex for $rm[Eu/Fe]$ with a small dispersion ($pm$0.1 dex). Every star analyzed with $rm[Fe/H] < -1.2$ belong to the $r$-process enhanced ($rm[Eu/Fe] > +0.3$ and $rm[Ba/Eu] < 0.0$) metal-poor category, providing remarkable evidence that, at such low-metallicity regime, stars of HStr experienced enrichment in neutron-capture elements predominantly via $r$-process nucleosynthesis. Finally, the extended metallicity range also suggests an increase in $rm[Ba/Eu]$ for higher $rm[Fe/H]$, in conformity with other surviving dwarf satellite galaxies of the Milky Way.
We investigate the origin of the abundance ratios and scatter of $alpha$- and neutron-capture elements of old, metal-poor stars, using cosmological, hydrodynamical simulations of galaxy formation. For this, we implement a novel treatment for the prod
We present an extensive analysis of the gas-phase abundances and depletion behaviors of neutron-capture elements in the interstellar medium (ISM). Column densities (or upper limits to the column densities) of Ga II, Ge II, As II, Kr I, Cd II, Sn II,
The close relationship between the nature of the Triangulum-Andromeda (TriAnd) overdensity and the Galactic disk has become increasingly evident in recent years. However, the chemical pattern of this overdensity (R$_{GC}$ = 20 - 30 kpc) is unique and
We analyze chemical abundances of stars in the Sagittarius (Sgr) tidal stream using high-resolution Gemini+GRACES spectra of 42 members of the highest surface brightness portions of both the trailing and leading arms. Targets were chosen using a 2MAS
The enrichment history of heavy neutron-capture elements in the Milky Way disc provides fundamental information about the chemical evolution of our Galaxy and about the stellar sources that made those elements. In this work we give new observational