J/A+A/705/A38 Molybdenum and Ruthenium in the Galactic Disc (Mishenina+, 2026)
Molybdenum and Ruthenium in the Galactic Disk:
A closer look at their nucleosynthesis components.
Mishenina T., Kurtukian-Nieto T., Gorbaneva T., Amarsi A.M., Psaltis A.,
Pignatari M.
<Astron. Astrophys. 705, A38 (2026)>
=2026A&A...705A..38M 2026A&A...705A..38M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, late-type ; Abundances ; Optical
Keywords: stars: abundances - stars: late-type - Galaxy: disk -
Galaxy: evolution
Abstract:
The stellar origin of the elements Molybdenum (Mo, Z=42) and Ruthenium
(Ru, Z=44) is still a matter of debate. Studying their abundances
provides valuable insights into the nucleosynthesis processes and the
broader evolution of neutron-capture elements.
The aim of this work is to present new observations of Mo and Ru,
together with nearby neutron-capture element Sr and Zr for a new
sample of 154 giant stars, located in the Galactic disk with
metallicity -1<[Fe/H]<+0.3.
The abundances are determined applying the Local Thermodynamic
Equilibrium by fitting synthetic spectra. The abundances of Mo were
derived from the MoI lines at 5506 and 5533Å, while the abundances
of Ru were determined from RuI lines at 4584, and 4757Å. The
abundances of strontium (Sr) and zirconium (Zr) measured using lines
of SrII at 4077 and 4215Å and of ZrI at 5385, 6127, and 613Å.
We derive Sr, Zr, and Mo abundances for all stars in our sample, and
Ru for 110 stars. For most of the giant stars observed in this work,
the Mo and Ru abundances were determined for the first time. We
compare our observations with the signature from different
nucleosynthesis processes.
Both the [Mo/Fe] and [Ru/Fe] in our stars show a decreasing trend with
respect to the increasing [Fe/H]. This pattern is similar to [Zr/Fe],
whereas [Sr/Fe] shows a rather at trend with respect to metallicity.
These results are compatible with our previous measurements obtained
for dwarf stars over the same metallicity range. Compared to the
s-process ratios, all stars show a lower [Zr/Mo] and a higher [Ru/Mo],
as expected from classical nucleosynthesis. Instead, it is unclear if
additional contributions from neutrino-wind components or the
i-process are needed to explain the observed scatter of [Zr/Mo] and
[Ru/Mo] in the Milky Way disk. Indeed, such a dispersion is compatible
with the variation also seen in r-II stars at low metallicity, and
therefore it could just be a product of the combination of r-process
and s-process contributions to Galactic Chemical Evolution. The
observed [Zr/Mo] and [Ru/Mo] scatter in r-II stars should be
constrained by future investigations to define if any contributions of
additional nucleosynthesis components are needed.
Description:
We present a new analysis of the abundances of molybdenum (Mo, Z=42)
and ruthenium (Ru, Z=44) in the Galactic disk (-1.0<[Fe/H]<+0.3),
based on a new sample of giant stars. New determinations of Mo and Ru
abundances were performed using high-resolution spectra
(R=42000) with signal-to-noise ratios (S/N) exceeding 100,
obtained with the ELODIE spectrographs (Observatoire de
Haute-Provence, France). Mo abundances were derived from MoI lines at
5506 and 5533Å for 154 stars, while Ru abundances were determined
from RuI lines at 4584 and 4757Å for 110 stars, using the LTE
approach with an accuracy of 0.15dex. For the majority of the target
giants, Mo and Ru abundances were determined for the first time.
Additionally, the abundances of strontium (Sr) and zirconium (Zr) were
also measured. In addition to the giants, we used data from the
stellar sample of dwarf stars from our previous papers (Mishenina et
al. 2019a,b, 2013) in our analysis. The abundance trends ([Sr/Fe],
[Zr/Fe], [Mo/Fe], and [Ru/Fe] with respect to [Fe/H]) are consistent
between the two sets of stars.
Table A1 presents the stellar parameters and the Sr, Zr, Mo, Ru
abundances with determination errors .
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
tablea1.dat 75 154 Stellar parameters and abundances of Sr, Zr, Mo, Ru
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Byte-by-byte Description of file: tablea1.dat
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Bytes Format Units Label Explanations
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1- 10 A10 -- ID Star identifier in the HD or BD catalogues
12- 15 I4 K Teff Effective temperature
17- 20 F4.2 [cm/s2] logg Surface gravity (logg)
22- 26 F5.2 --- [Fe/H] Metallicity [Fe/H]
28- 31 F4.2 km/s Vt Microturbulent velocity
33- 37 F5.2 --- [Sr/Fe] ?=- Abundance [Sr/Fe]
39- 42 F4.2 --- e_[Sr/Fe] ?=- Error on [Sr/Fe]
44- 48 F5.2 --- [Zr/Fe] ?=- Abundance [Zr/Fe]
50- 53 F4.2 --- e_[Zr/Fe] ?=- Error on [Zr/Fe]
55- 59 F5.2 --- [Mo/Fe] ?=- Abundance [Mo/Fe]
61- 64 F4.2 --- e_[Mo/Fe] ?=- Error on [Mo/Fe]
66- 70 F5.2 --- [Ru/Fe] ?=- Abundance [Ru/Fe]
72- 75 F4.2 --- e_[Ru/Fe] ?=- Error on [Ru/Fe]
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Acknowledgements:
Tamara Mishenina, tmishenina(at)ukr.net
(End) Patricia Vannier [CDS] 24-Nov-2025