J/A+A/704/A282 The R-Process Alliance (Racca+, 2025)
The R-Process Alliance: Exploring the cosmic scatter among ten r-process sites
with stellar abundances.
Racca M., Hansen T.T., Roederer I.U., Placco V.M., Frebel A., Beers T.C.,
Ezzeddine R., Holmbeck E.M., Sakari C.M., Monty S., Harket O., Simon J.D.,
Sneden C., Thompson I.B.
<Astron. Astrophys. 704, A282 (2025)>
=2025A&A...704A.282R 2025A&A...704A.282R (SIMBAD/NED BibCode)
ADC_Keywords: Stars, metal-deficient ; Stars, population II ; Abundances
Keywords: stars: abundances - stars: chemically peculiar -
stars: kinematics and dynamics - stars: low-mass - Galaxy: abundances
Abstract:
The astrophysical origin of the rapid neutron-capture process
(r-process), responsible for producing roughly half of the
elements heavier than iron, remains uncertain. Detailed chemical
signatures from the oldest, most metal-poor stars, which act as fossil
records of the earliest nucleosynthesis events, can be used to
identify the dominant r-process sites.
We present a homogeneous chemical abundance analysis of ten r-process
element-enhanced stars. These old and metal-poor stars are strongly
enriched in r-process elements with minimal contamination from other
nucleosynthetic sources. By focusing on this chemically pure sample,
we aim to investigate intrinsic variations in the r-process abundance
patterns and explore their implications for the nature and potential
diversity of r-process sites.
We performed a detailed chemical abundance analysis of
high-resolution, high signal-to-noise spectra. For each star, we
inspected over 1400 individual absorption lines using a combination of
equivalent width measurements and spectral synthesis. The analysis was
conducted under the assumption of one-dimensional local thermodynamic
equilibrium, employing the MOOG radiative transfer code.
We derived abundances for 54 chemical species, including 29
neutron-capture (n-capture) elements covering the full mass range of
the r-process abundance pattern. A kinematic analysis reveals that
stars likely originated from ten kinematically distinct systems. Based
on this assumption, we use the sample to probe the maximum variation
expected from ten independent r-process nucleosynthesis events and
compute the intrinsic dispersion of each element relative to Zr and
Eu, for the light and heavy r-process elements, respectively. This
exercise results in a remarkably low cosmic scatter across the ten
r-process sites enriching these stars, for the rare earth and third
peak elements, for example, we find σ[La/Eu]=0.08 and
σ[Os/Eu]=0.11dex while the scatter between light and heavy,
σ[Zr/Eu] is slightly higher at 0.18dex.
The elemental abundance patterns across the ten independent r-process
sites show remarkably small cosmic dispersions. This minimal
dispersion suggests a high degree of uniformity in r-process yields
across diverse astrophysical environments.
Description:
This catalogue provides the atomic line lists and elemental-abundance
tables used in the spectroscopic analysis of ten metal-poor stars from
the paper. The material is organized into two type of files:
Each star has two associated data files:
- A line list of all measured transitions used in the analysis,
including atomic data, equivalent widths or synthesis flags, and
derived abundances.
- A summary table of the final abundances for all detected elements,
including the number of lines used and associated uncertainties.
Based on spectra obtained with Magellan Inamori Kyocera Echelle (MIKE)
spectrograph on the Landon Clay (Magellan II) telescope at Las
Campanas Observatory, Chile; and the TS23 echelle spectrograph on the
Harlan J. Smith 107-inch (2.7m) telescope at McDonald Observatory.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 147 10 Properties of the stars
rlj00p27.dat 63 549 J0040+2729 all spectral lines used in the
abundance analysis
rlj02m15.dat 63 594 J0246-1518 all spectral lines used in the
abundance analysis
rlj02m19.dat 63 565 J0217-1903 all spectral lines used in the
abundance analysis
rlj14m23.dat 63 528 J1430-2371 all spectral lines used in the
abundance analysis
rlj14m41.dat 63 749 J1432-4125 all spectral lines used in the
abundance analysis
rlj19m55.dat 63 605 J1916-5544 all spectral lines used in the
abundance analysis
rlj20m34.dat 63 449 J2009-3410 all spectral lines used in the
abundance analysis
rlj20m51.dat 63 513 J2049-5124 all spectral lines used in the
abundance analysis
rlj21m13.dat 63 777 J2109-1310 all spectral lines used in the
abundance analysis
rlj21m68.dat 63 422 J2106-6828 all spectral lines used in the
abundance analysis
abj00p27.dat 61 46 J0040+2729 all detected elements from light
to neutron-capture species
abj02m15.dat 61 45 J0246-1518 all detected elements from light
to neutron-capture species
abj02m19.dat 61 50 J0217-1903 all detected elements from light
to neutron-capture species
abj14m23.dat 61 52 J1430-2371 all detected elements from light
to neutron-capture species
abj14m41.dat 61 50 J1432-4125 all detected elements from light
to neutron-capture species
abj19m55.dat 61 48 J1916-5544 all detected elements from light
to neutron-capture species
abj20m34.dat 61 51 J2009-3410 all detected elements from light
to neutron-capture species
abj20m51.dat 61 52 J2049-5124 all detected elements from light
to neutron-capture species
abj21m13.dat 61 52 J2109-1310 all detected elements from light
to neutron-capture species
abj21m68.dat 61 39 J2106-6828 all detected elements from light
to neutron-capture species
refs.dat 165 53 References
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 17 A17 --- 2MASS 2MASS name (JHHMMSSss+DDMMSSs)
19- 20 I2 h RAh Right ascension (J2000)
22- 23 I2 min RAm Right ascension (J2000)
25- 28 F4.1 s RAs Right ascension (J2000)
30 A1 --- DE- Declination sign (J2000)
31- 32 I2 deg DEd Declination (J2000)
34- 35 I2 arcmin DEm Declination (J2000)
37- 40 F4.1 arcsec DEs Declination (J2000)
42- 46 F5.2 mag Vmag V magnitude (1)
48- 51 F4.2 mag e_Vmag V magnitude error (1)
53- 57 F5.2 mag Gmag Gaia DR3 G magnitude
59- 63 F5.2 mag Bpmag Gaia DR3 Bp magnitude
65- 69 F5.2 mag Rpmag Gaia DR3 Rp magnitude
71- 75 F5.2 mag Kmag K magnitude (1)
77- 80 F4.2 mag e_Kmag K magnitude error (1)
82- 87 F6.4 mag E(B-V) Reddening
89- 94 F6.4 mag e_E(B-V) Reddening error
96- 99 F4.2 mas plx Gaia DR3 parallax
101-104 F4.2 mas e_plx Gaia DR3 parallax error
106-115 A10 --- SName Short name
117-121 F5.2 --- SCorr ? S correction
123-134 A12 --- RLTable Name of the all spectral lines table
for this source
136-147 A12 --- AbTable Name of the all detected elements table
for this source
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Note (1): V and K magnitudes are taken respectively from
Munari et al. (2014AJ....148...81M 2014AJ....148...81M, Cat. J/AJ/148/81) and
Cutri et al. (2003, Cat. II/246).
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Byte-by-byte Description of file: rl*.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 0.1nm lambda Wavelength
14- 19 A6 --- Species Element and ionization stage
23- 26 F4.2 eV EP ?=- Excitation potential
30- 34 F5.2 [-] loggf ?=- Oscillator strength
38- 40 A3 --- Method Method (1)
46- 51 F6.2 0.1pm EW ?=- Equivalent width
(for eqw lines; '--' for syn)
55- 59 F5.2 [-] log(eps) ?=- Derived abundance
62- 63 I2 --- Ref ?=-1 Literature source of log(gf)
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Note (1): Method as follows:
eqw = equivalent-width measurement
syn = spectral synthesis
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Byte-by-byte Description of file: abj*dat
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Bytes Format Units Label Explanations
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1- 5 F5.1 --- Species Species
8- 11 A4 --- El Element
14- 16 I3 --- Nlines Number of transitions used
21- 25 F5.2 [-] log(eps) Mean abundance
30- 34 F5.2 [-] [X/H] Abundance relative to solar
40- 43 F4.2 [-] e_[X/H] ?=- Uncertainty in [X/H]
48- 52 F5.2 [-] [X/Fe] Abundance relative to iron
58- 61 F4.2 [-] e_[X/Fe] ?=- Uncertainty in [X/Fe]
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Ref Reference code
4- 22 A19 ---- BibCode BibCode
24- 46 A23 --- Aut Author's name
48-197 A150 --- Com Comments
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Acknowledgements:
Mila Racca, mila.racca(at)astro.su.se
(End) Patricia Vannier [CDS] 19-Nov-2025