J/A+A/693/A293 CERES III. Abundances for 52 stars (Lombardo+, 2025)
Chemical Evolution of R-process Elements in Stars (CERES).
III. Chemical abundances of neutron capture elements from Ba to Eu.
Lombardo L., Hansen C.J., Rizzuti F., Cescutti G., Mashonkina L.I.,
Francois P., Bonifacio P., Caffau E., Alencastro Puls A.,
Fernandes de Melo R., Gallagher A.J., Skuladottir A., Koch Hansen A.J.,
Sbordone L.
<Astron. Astrophys. 693, A293 (2025)>
=2025A&A...693A.293L 2025A&A...693A.293L (SIMBAD/NED BibCode)
ADC_Keywords: Stars, giant ; Abundances ; Optical
Keywords: nuclear reactions, nucleosynthesis, abundances -
stars: abundances - stars: Population II - Galaxy: abundances -
Galaxy: stellar content
Abstract:
The chemical abundances of elements such as barium and the lanthanides
are essential to understand the nucleosynthesis of heavy elements in
the early Universe as well as the contribution of different neutron
capture processes (e.g. slow versus rapid) at different epochs. The
Chemical Evolution of R-process Elements in Stars (CERES) project aims
to provide a homogeneous analysis of a sample of metal-poor stars
([Fe/H]←1.5) to improve our understanding of the nucleosynthesis of
neutron capture elements, in particular the r-process elements, in the
early Galaxy. Our data consist of a sample of high resolution and high
signal-to-noise ratio UVES spectra. The chemical abundances were
derived through spectrum synthesis, using the same model atmospheres
and stellar parameters as derived in the first paper of the CERES
series. We measured chemical abundances or upper limits of seven heavy
neutron capture elements (Ba, La, Ce, Pr, Nd, Sm, and Eu) for a sample
of 52 metal-poor giant stars. We estimated through the mean shift
clustering algorithm that at [Ba/H]=-2.4 and [Fe/H]=-2.4 a variation
in the trend of [X/Ba], with X=La,Nd,Sm,Eu, versus [Ba/H] occurs. This
result suggests that, for [Ba/H]←2.4, Ba nucleosynthesis in the Milky
Way halo is primarily due to the r-process, while for [Ba/H]>-2.4 the
effect of the s-process contribution begins to be visible. In our
sample, stars with [Ba/Eu] compatible with Solar system pure r-process
value (hereafter, r-pure) do not show any particular trend compared to
other stars, suggesting r-pure stars may form in similar environments
to stars with less pure r-process enrichments. Homogeneous
investigations of high resolution and signal-to-noise ratio spectra
are crucial for studying the heavy elements formation, as they provide
abundances that can be used to test nucleosynthesis models as well as
Galactic chemical evolution models.
Description:
We present a homogeneous chemical abundance analysis of elements from
Ba to Eu for a sample of 52 Galactic halo giant stars with
[Fe/H]≤-1.79.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
stars.dat 53 52 Sample stars
table1.dat 212 52 Chemical abundances with uncertainties for
our sample of stars
--------------------------------------------------------------------------------
See also:
J/A+A/665/A10 : CERES I. Abundances for 52 star (Lombardo+, 2022)
Byte-by-byte Description of file: stars.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 16 A16 --- Name Star name
18- 29 A12 --- Star Stellar name (CESHHMM+DDMM)
31- 32 I2 h RAh Right ascension (J2000)
34- 35 I2 min RAm Right ascension (J2000)
37- 41 F5.2 s RAs Right ascension (J2000)
43 A1 --- DE- Declination sign (J2000)
44- 45 I2 deg DEd Declination (J2000)
47- 48 I2 arcmin DEm Declination (J2000)
50- 53 F4.1 arcsec DEs Declination (J2000)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 A12 --- Star Stellar name (CESHHMM+DDMM)
14- 18 F5.2 --- [FeII/H] FeII abundance relative to the Sun
20 I1 --- o_Ba Number of BaII lines used
22- 26 F5.2 --- A(Ba) ? Ba abundance from BaII lines
28- 32 F5.2 --- sigma(Ba) ? Line-to-line scatter for BaII lines
34- 38 F5.2 --- [Ba/H] ? Ba abundance relative to the Sun
40- 44 F5.2 --- [Ba/Fe] ? BaII over FeII abundance ratio
46 I1 --- o_La Number of LaII lines used
48 A1 --- l_A(La) Upper limit flag on La abundance
50- 54 F5.2 --- A(La) ? La abundance from LaII lines
56- 60 F5.2 --- sigma(La) ? Line-to-line scatter for LaII lines
62- 66 F5.2 --- [La/H] ? La abundance relative to the Sun
68- 72 F5.2 --- [La/Fe] ? LaII over FeII abundance ratio
74 I1 --- o_Ce Number of CeII lines used
76 A1 --- l_A(Ce) Upper limit flag on Ce abundance
78- 82 F5.2 --- A(Ce) ? Ce abundance from CeII lines
84- 88 F5.2 --- sigma(Ce) ? Line-to-line scatter for CeII lines
90- 94 F5.2 --- [Ce/H] ? Ce abundance relative to the Sun
96-100 F5.2 --- [Ce/Fe] ? CeII over FeII abundance ratio
102 I1 --- o_Pr Number of PrII lines used
104 A1 --- l_A(Pr) Upper limit flag on Pr abundance
106-110 F5.2 --- A(Pr) ? Pr abundance from PrII lines
112-116 F5.2 --- sigma(Pr) ? Line-to-line scatter for PrII lines
118-122 F5.2 --- [Pr/H] ? Pr abundance relative to the Sun
124-128 F5.2 --- [Pr/Fe] ? PrII over FeII abundance ratio
130 I1 --- o_Nd Number of NdII lines used
132 A1 --- l_A(Nd) Upper limit flag on Nd abundance
134-138 F5.2 --- A(Nd) Nd abundance from NdII lines
140-144 F5.2 --- sigma(Nd) ? Line-to-line scatter for NdII lines
146-150 F5.2 --- [Nd/H] Nd abundance relative to the Sun
152-156 F5.2 --- [Nd/Fe] NdII over FeII abundance ratio
158 I1 --- o_Sm Number of SmII lines used
160 A1 --- l_A(Sm) Upper limit flag on Sm abundance
162-166 F5.2 --- A(Sm) ? Sm abundance from SmII lines
168-172 F5.2 --- sigma(Sm) ? Line-to-line scatter for SmII lines
174-178 F5.2 --- [Sm/H] ? Sm abundance relative to the Sun
180-184 F5.2 --- [Sm/Fe] ? SmII over FeII abundance ratio
186 I1 --- o_Eu Number of EuII lines used
188 A1 --- l_A(Eu) Upper limit flag on Eu abundance
190-194 F5.2 --- A(Eu) Eu abundance from EuII lines
196-200 F5.2 --- sigma(Eu) ? Line-to-line scatter for EuII lines
202-206 F5.2 --- [Eu/H] Eu abundance relative to the Sun
208-212 F5.2 --- [Eu/Fe] EuII over FeII abundance ratio
--------------------------------------------------------------------------------
Acknowledgements:
Linda Lombardo, Lombardo(at)iap.uni-frankfurt.de
References:
Lombardo et al., Paper I 2022A&A...665A..10L 2022A&A...665A..10L, Cat. J/A+A/665/A10
(End) Patricia Vannier [CDS] 22-Nov-2024