J/A+A/683/A73 s-process abundances in halo stars (Guiglion+, 2024)
Observational constraints on the origin of the elements.
VIII. Constraining the barium, strontium, and yttrium chemical evolution in
metal-poor stars.
Guiglion G., Bergemann M., Storm N., Lian J., Cescutti G., Serenelli A.
<Astron. Astrophys. 683, A73 (2024)>
=2024A&A...683A..73G 2024A&A...683A..73G (SIMBAD/NED BibCode)
ADC_Keywords: Milky Way; Stars, F-type ; Stars, G-type ; Stars, K-type ;
Abundances ; Spectroscopy
Keywords: stars: abundances - ISM: abundances - Galaxy: abundances -
Galaxy: evolution - Galaxy: stellar content
Abstract:
The chemical evolution history of slow neutron-capture elements in the
Milky Way is still a matter of debate, especially in the metal-poor
regime ([Fe/H]←1). Based on Gaia-ESO spectroscopic data, a recent
study investigated the chemical evolution of neutron-capture elements
in the regime [Fe/H]>-1. Here, we aim to complement this study down to
[Fe/H]=-3, and focus on Ba, Y, and Sr, along with the abundance ratios
of [Ba/Y] and [Sr/Y], which give comprehensive views on s-process
nucleosynthesis channels.
We measured the local thermodynamic equilibrium (LTE) and non-local
thermodynamic equilibrium (NLTE) abundances of Ba, Y, and Sr in 323
Galactic metal-poor stars using high-resolution optical spectra with
high signal-to-noise ratios. We used the spectral fitting code TSFitPy
together with 1D model atmospheres, using previously determined LTE
and NLTE atmospheric parameters.
We find that the NLTE effects are on the order of ~-0.1 to ∼0.2dex,
depending on the element. We find that stars enhanced(deficient) in
[Ba/Fe] and [Y/Fe] are also enhanced(deficient) in [Sr/Fe], suggesting
a common evolution channel for these three elements. We find that the
ratio between heavy and light s-process elements [Ba/Y] varies weakly
with [Fe/H] even in the metal-poor regime, which is consistent with
the behaviour in the metal-rich regime. The [Ba/Y] scatter at a given
metallicity is larger than the abundance measurement uncertainties.
Homogeneous chemical evolution models with different yield
prescriptions are not able to accurately reproduce the [Ba/Y] scatter
in the low-[Fe/H] regime. Adopting the stochastic chemical evolution
model by Cescutti & Chiappini (2014A&A...565A..51C 2014A&A...565A..51C) allows us to
reproduce the observed scatter in the abundance pattern of [Ba/Y] and
[Ba/Sr]. Based on our observations, we have ruled out the need for an
arbitrary scaling of the r-process contribution, as previously
suggested by the authors behind the construction of the model.
We show how important it is to properly include NLTE effects when
measuring chemical abundances, especially in the metal-poor regime.
This work demonstrates that the choice of the Galactic chemical
evolution model (stochastic versus one-zone) is key when comparing
models to observations. Upcoming large-scale spectroscopic surveys
such as 4MOST and WEAVE are poised to deliver high-quality data for
many thousands of metal-poor stars and this work gives a typical case
study of what could be achieved with such surveys in the future.
Description:
Thanks to high resolution spectra from Ruchti et al.
(2011ApJ...743..107R 2011ApJ...743..107R) and high quality LTE and NLTE atmospheric
parameters from Ruchti et al. (2013MNRAS.429..126R 2013MNRAS.429..126R, Cat.
J/MNRAS/429/126), we dervied chemical abundances of Y, Sr, and Ba for
323 stars, using an automatic spectral fitting method.
We provide the star identifier, [Fe/H], [Sr/Fe], [Y/Fe], and [Ba/Fe]
in LTE and NLTE and associated errors. We also provide individual line
abundances.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
abund.dat 181 323 Catalogue of abundances
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See also:
J/A+A/631/A80 : Mn lines 3D NLTE formation in late-type stars (Bergemann+ 2019)
Byte-by-byte Description of file: abund.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- ID Target ID
17- 21 F5.2 [-] [Fe/H]LTE LTE [Fe/H] ratio
23- 27 F5.2 [-] [Fe/H]NLTE NLTE [Fe/H] ratio
29- 34 F6.3 [-] [Ba/Fe]LTE ?=-9.999 Abundance ratio [Ba/Fe] in LTE
36- 41 F6.3 [-] e_[Ba/Fe]LTE ?=-9.999 Uncertainty on LTE [Ba/Fe]
43- 48 F6.3 [-] [Ba/Fe]NLTE ?=-9.999 Abundance ratio [Ba/Fe] in NLTE
50- 55 F6.3 [-] e_[Ba/Fe]NLTE ?=-9.999 Uncertainty on NLTE [Ba/Fe]
57- 62 F6.3 [-] [Sr/Fe]LTE ?=-9.999 Abundance ratio [Sr/Fe] in LTE
64- 69 F6.3 [-] e_[Sr/Fe]LTE ?=-9.999 Uncertainty on LTE [Sr/Fe]
71- 76 F6.3 [-] [Sr/Fe]NLTE ?=-9.999 Abundance ratio [Sr/Fe] in NLTE
78- 83 F6.3 [-] e_[Sr/Fe]NLTE ?=-9.999 Uncertainty on NLTE [Sr/Fe]
85- 90 F6.3 [-] [Y/Fe]LTE ?=-9.999 Abundance ratio [Y/Fe] in LTE
92- 97 F6.3 [-] e_[Y/Fe]LTE ?=-9.999 Uncertainty on LTE [Y/Fe]
99-104 F6.3 [-] [Y/Fe]NLTE ?=-9.999 Abundance ratio [Y/Fe] in NLTE
106-111 F6.3 [-] e_[Y/Fe]NLTE ?=-9.999 Uncertainty on NLTE [Y/Fe]
113-118 F6.3 [-] [Ba/Fe]LTE5853 ?=-9.999 Abundance ratio [Ba/Fe] in LTE
from line at 5853Å
120-125 F6.3 [-] [Ba/Fe]LTE6141 ?=-9.999 Abundance ratio [Ba/Fe] in LTE
from line at 6141Å
127-132 F6.3 [-] [Ba/Fe]LTE6496 ?=-9.999 Abundance ratio [Ba/Fe] in LTE
from line at 6496Å
134-139 F6.3 [-] [Ba/Fe]NLTE5853 ?=-9.999 Abundance ratio [Ba/Fe] in NLTE
from line at 5853Å
141-146 F6.3 [-] [Ba/Fe]NLTE6141 ?=-9.999 Abundance ratio [Ba/Fe] in NLTE
from line at 6141Å
148-153 F6.3 [-] [Ba/Fe]NLTE6496 ?=-9.999 Abundance ratio [Ba/Fe] in NLTE
from line at 6496Å
155-160 F6.3 [-] [Y/Fe]LTE4883 ?=-9.999 Abundance ratio [Y/Fe] in LTE
from line at 4883Å
162-167 F6.3 [-] [Y/Fe]LTE5087 ?=-9.999 Abundance ratio [Y/Fe] in LTE
from line at 5087Å
169-174 F6.3 [-] [Y/Fe]NLTE4883 ?=-9.999 Abundance ratio [Y/Fe] in NLTE
from line at 4883Å
176-181 F6.3 [-] [Y/Fe]NLTE5087 ?=-9.999 Abundance ratio [Y/Fe] in NLTE
from line at 5087Å
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Acknowledgements:
Guillaume Guiglion, gguiglion(at)aip.de
References:
Bergemann et al., Paper I 2019A&A...631A..80B 2019A&A...631A..80B, Cat. J/A+A/631/A80
Gallagher et al., Paper II 2020A&A...634A..55G 2020A&A...634A..55G
Eitner et al., Paper III 2020A&A...635A..38E 2020A&A...635A..38E
Magg et al., Paper IV 2022A&A...661A.140M 2022A&A...661A.140M
Eitner et al., Paper V 2023A&A...677A.151E 2023A&A...677A.151E
Lian et al., Paper VI 2023MNRAS.525.1329L 2023MNRAS.525.1329L
Storm & Bergemann, Paper VII 2023MNRAS.525.3718S 2023MNRAS.525.3718S
(End) Guillaume Guiglion [ZAH/LSW, Germany], Patricia Vannier [CDS] 05-Jan-2024