In:
The Astrophysical Journal Letters, American Astronomical Society, Vol. 913, No. 2 ( 2021-06-01), p. L28-
Abstract:
We identified eight 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 ∼0.5 dex) metallicity interval (− 2.5 ≲ [Fe/H] 〈 − 1.0) than previously reported. Our study focuses on α (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 [ α /Fe] for increasing metallicity up to [Fe/H] ∼ −1.0. Moreover, stars of HStr show a median value of +0.5 dex for [Eu/Fe] with a small dispersion (±0.1 dex). Every star analyzed with [Fe/H] 〈 −1.2 belongs to the r -process enhanced ([Eu/Fe] 〉 +0.3 and [Ba/Eu] 〈 0.0) metal-poor category, providing remarkable evidence that, at such a 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 [Ba/Eu] for higher [Fe/H] , in conformity with other surviving dwarf satellite galaxies of the Milky Way.
Type of Medium:
Online Resource
ISSN:
2041-8205
,
2041-8213
DOI:
10.3847/2041-8213/ac0056
Language:
Unknown
Publisher:
American Astronomical Society
Publication Date:
2021
detail.hit.zdb_id:
2207648-7
detail.hit.zdb_id:
2006858-X
