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Context. The origin of the large star-to-star variation of the [Eu/Fe] ratios observed in the extremely metal-poor (at [Fe/H]$\leq-3$) stars of the Galactic halo is still a matter of debate.\\ Aims. In this paper, we explore this problem by…

Astrophysics of Galaxies · Physics 2023-06-21 L. Cavallo , G. Cescutti , F. Matteucci

In this work we present and discuss the observations of the Mn abundances for 247 FGK dwarfs, located in the Galactic disc with metallicity -1<Fe/H]<+0.3. The observed stars belong to the substructures of the Galaxy thick and thin discs,…

Astrophysics of Galaxies · Physics 2015-10-14 T. Mishenina , T. Gorbaneva , M. Pignatari , F. -K. Thielemann , S. A. Korotin

To understand the formation and evolution of the different stellar populations within our Galaxy it is essential to combine detailed kinematical and chemical information for large samples of stars. We derive chemical abundances of Cu, Zn,…

Solar and Stellar Astrophysics · Physics 2017-10-25 E. Delgado Mena , M. Tsantaki , V. Zh. Adibekyan , S. G. Sousa , N. C. Santos , J. I. González Hernández , G. Israelian

The metallicity distribution function (MDF) of the Galactic bulge features a multi-peak shape, with a metal-poor peak at [Fe/H]=-0.3 dex and a metal-rich peak at [Fe/H]=+0.3 dex. This bimodality is also seen in [alpha/Fe] versus [Fe/H]…

Astrophysics of Galaxies · Physics 2024-05-22 M. Molero , F. Matteucci , E. Spitoni , A. Rojas-Arriagada , R. M. Rich

The heaviest chemical elements are naturally produced by the rapid neutron-capture process (r-process) during neutron star mergers or supernovae. The r-process production of elements heavier than uranium (transuranic nuclei) is poorly…

Comparing observational abundance features with nucleosynthesis predictions of stellar evolution or explosion simulations can scrutinize two aspects: (a) the conditions in the astrophysical production site and (b) the quality of the nuclear…

Canonical theory predicts galaxies grow "inside-out", producing their observed negative radial age gradient. This picture is challenged by galaxies' `U-shaped' colour profiles -- indicating reversed age gradient -- explained by either…

Astrophysics of Galaxies · Physics 2026-05-25 Jianhui Lian , Qinhao Shao , Yuze Zhao

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 (for example…

Based on a simple, but fairly successful, model of the chemical evolution of the Milky Way disk, we study the evolution of the abundances of the elements He, C, N, O, Ne, Mg, Al, Si, S, Ar and Fe. We use metallicity dependent yields for…

Astrophysics · Physics 2007-05-23 J. L. Hou , N. Prantzos , S. Boissier

Spectroscopic surveys of the Galaxy reveal that its disc stars exhibit a spread in $\mathrm{[\alpha/Fe]}$ at fixed $\mathrm{[Fe/H]}$, manifest at some locations as a bimodality. The origin of these diverse, and possibly distinct, stellar…

Astrophysics of Galaxies · Physics 2018-05-02 J. Ted Mackereth , Robert A. Crain , Ricardo P. Schiavon , Joop Schaye , Tom Theuns , Matthieu Schaller

From newly-obtained high-resolution, high signal-to-noise ratio spectra the abundances of the elements La and Eu have been determined over the stellar metallicity range -3<[Fe/H]<+0.3 in 159 giant and dwarf stars. Lanthanum is predominantly…

Astrophysics · Physics 2009-11-10 J. Simmerer , C. Sneden , J. J. Cowan , J. Collier , V. M. Woolf , J. E. Lawler

Recent spectroscopic studies have revealed the presence of numerous carbon-enhanced, metal-poor stars with [Fe/H] < -2.0 that exhibit strong enhancements of s-process elements. These stars are believed to be the result of a binary…

Astrophysics · Physics 2009-11-13 S. Wanajo , K. Nomoto , N. Iwamoto , Y. Ishimaru , T. C. Beers

We determined the chemical and kinematic properties of the Galactic thin and thick disk using a sample of 307,246 A/F/G/K-type giant stars from the LAMOST spectroscopic survey and Gaia DR2 survey. Our study found that the thick disk…

Astrophysics of Galaxies · Physics 2019-07-31 Yepeng Yan , Cuihua Du , Shuai Liu , Hefan Li , Jianrong Shi , Yuqin Chen , Jun Ma , Zhenyu Wu

There has been a persistent conundrum in attempts to model the nucleosynthesis of heavy elements by rapid neutron capture (the $r$-process). Although the location of the abundance peaks near nuclear mass numbers 130 and 195 identify an…

Solar and Stellar Astrophysics · Physics 2016-01-27 S. Shibagaki , T. Kajino , G. J. Mathews , S. Chiba , S. Nishimura , G. Lorusso

The detailed chemical composition of most metal-poor halo stars has been found to be highly uniform, but a minority of stars exhibit dramatic enhancements in their abundances of heavy neutron-capture elements and/or of carbon. The key…

Solar and Stellar Astrophysics · Physics 2015-11-04 T. T. Hansen , J. Andersen , B. Nordstrøm , T. C. Beers , J. Yoon , L. A. Buchhave

We investigate the evolution of galactic disks in N-body Tree-SPH simulations. We find that disks, initially truncated at three scale-lengths, can triple their radial extent, solely driven by secular evolution. Both Type I (single…

Astrophysics of Galaxies · Physics 2015-06-04 I. Minchev , B. Famaey , A. C. Quillen , P. Di Matteo , F. Combes , M. Vlajic , P. Erwin , J. Bland-Hawthorn

Recent dynamical analysis based on Gaia data have revealed major accretion events in Milky Way's history. Nevertheless, our understanding of the primordial Galaxy is hindered because the bona fide identification of the most metal-poor and…

We analyze data from several studies of metal-poor stars in the Milky Way, focusing on both strong (Eu) and weak (Sr) $r$-process elements. Because these elements were injected in an explosion, we calculate the mass swept up when the blast…

High Energy Astrophysical Phenomena · Physics 2018-09-12 Phillip Macias , Enrico Ramirez-Ruiz

Despite the recent advancements in the field of galaxy formation and evolution, fully self-consistent simulations are still unable to make the detailed predictions necessary for the planned and ongoing large spectroscopic and photometry…

Astrophysics of Galaxies · Physics 2019-08-19 Ivan Minchev , Cristina Chiappini , Marie Martig

We have recently identified a new radial migration mechanism resulting from the overlap of spiral and bar resonances in galactic disks. Here we confirm the efficiency of this mechanism in fully self-consistent, Tree-SPH simulations, as well…

Astrophysics of Galaxies · Physics 2015-05-19 I. Minchev , B. Famaey , F. Combes , P. Di Matteo , M. Mouhcine , H. Wozniak