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The dominant site(s) of the $r$-process are a subject of current debate. Ejecta from $r$-process enrichment events like kilonovae are difficult to directly measure, so we must instead probe abundances in metal-poor stars to constrain…

Solar and Stellar Astrophysics · Physics 2025-11-17 John D. Dixon , Rana Ezzeddine , Yangyang Li , Thibault Merle , Manuel Bautista , Yanjun Guo

Our aim is to measure accurate, homogeneous neutron-capture element abundances for the sample of 32 EMP giant stars studied earlier in this series, including 22 stars with [Fe/H] $< -$3.0. Based on high-resolution, high S/N spectra from the…

We report an abundance analysis for the highly r-process-enhanced (r-II) star CS 29497-004, a very metal-poor giant with Teff = 5013K and [Fe/H]=-2.85, whose nature was initially discovered in the course of the HERES project. Our analysis…

Astrophysics of Galaxies · Physics 2017-11-22 V. Hill , N. Christlieb , T. C. Beers , P. S. Barklem , K. -L. Kratz , B. Nordström , B. Pfeiffer , K. Farouqi

A clear definition of the contribution from the slow neutron-capture process (s process) to the solar abundances between Fe and the Sr-Zr region is a crucial challenge for nuclear astrophysics. Robust s-process predictions are necessary to…

Solar and Stellar Astrophysics · Physics 2025-10-22 Marco Pignatari , Roberto Gallino , Rene Reifarth

We follow the chemical evolution of the Galaxy for elements from Ba to Eu, using an evolutionary model suitable to reproduce a large set of Galactic (local and non local) and extragalactic constraints. Input stellar yields for neutron-rich…

Astrophysics · Physics 2009-10-31 C. Travaglio , D. Galli , R. Gallino , M. Busso , F. Ferrini , O. Straniero

There are many candidate sites of the r-process: core-collapse supernovae (including rare magnetorotational core-collapse supernovae), neutron star mergers, and neutron star/black hole mergers. The chemical enrichment of…

Astrophysics of Galaxies · Physics 2018-12-19 Gina E. Duggan , Evan N. Kirby , Serge M. Andrievsky , Sergey A. Korotin

We present a comprehensive abundance analysis of two newly-discovered carbon-enhanced metal-poor (CEMP) stars. HE2138-3336 is a s-process-rich star with [Fe/H] = -2.79, and has the highest [Pb/Fe] abundance ratio measured thus far, if NLTE…

In this study, abundances of the neutron-capture elements Rb, Sr, and Zr are derived, for the first time, in a sample of nearby M dwarfs. We focus on stars in the metallicity range -0.5<[Fe/H]<+0.3, an interval poorly explored for Rb…

M15 is a globular cluster with a known spread in neutron-capture elements. This paper presents abundances of neutron-capture elements for 62 stars in M15. Spectra were obtained with the Michigan/Magellan Fiber System (M2FS) spectrograph,…

Small stellar systems like dwarf galaxies are suggested to be the main building blocks of our Galaxy by numerical simulations in Lambda CDM models. The existence of star streams like Sagittarius tidal stream indicates that dwarf galaxies…

Solar and Stellar Astrophysics · Physics 2019-05-13 Qian-Fan Xing , Gang Zhao , Wako Aoki , Satoshi Honda , Hai-Ning Li , Miho N. Ishigaki , Tadafumi Matsuno

The aim of this work is to determine abundances of neutron-capture elements for thin- and thick-disc F, G, and K stars in several sky fields near the north ecliptic pole and to compare the results with the Galactic chemical evolution…

We determine relative abundance ratios for the neutron-capture elements Zr, La, Ce, Nd, and Eu for a sample of 27 Galactic dwarf stars with -1.5 < [Fe/H] <-0.8. We also measure the iron-peak element Sc. These stars separate into three…

Solar and Stellar Astrophysics · Physics 2017-01-18 C. K. Fishlock , D. Yong , A. I. Karakas , A. Alves-Brito , J. Melendez , P. E. Nissen , C. Kobayashi , A. R. Casey

We use observations of heavy elements in very metal-poor stars ([Fe/H] < -2.5) in order to place constraints on the viability of collapsar models as a significant source of the r-process. We combine bipolar explosion nucleosynthesis…

High Energy Astrophysical Phenomena · Physics 2019-06-05 Phillip Macias , Enrico Ramirez-Ruiz

We present a model to explain the wide range of abundances for heavy r-process elements (mass number A > 130) at low [Fe/H]. This model requires rapid star formation and/or an initial population of supermassive stars in the earliest…

Astrophysics · Physics 2009-10-31 G. J. Wasserburg , Y. -Z. Qian

The existence of neutron star mergers has been supported since the discovery of the binary pulsar and the observation of its orbital energy loss, consistent with General Relativity. They are considered nucleosynthesis sites of the rapid…

High Energy Astrophysical Phenomena · Physics 2017-10-09 F. -K. Thielemann , M. Eichler , I. V. Panov , B. Wehmeyer

Studies of nucleosynthesis in neutrino-driven winds from nascent neutron stars show that the elements from Sr through Ag with mass numbers A~88-110 are produced by charged-particle reactions (CPR) during the alpha-process in the winds.…

Astrophysics · Physics 2009-11-13 Y. -Z. Qian , G. J. Wasserburg

Neutron-star mergers were recently confirmed as sites of rapid-neutron-capture (r-process) nucleosynthesis. However, in Galactic chemical evolution models, neutron-star mergers alone cannot reproduce the observed element abundance patterns…

We present a detailed chemical abundance analysis of HE 1300+0157, a subgiant with [Fe/H]=-3.9. From a high-resolution, high-S/N Subaru/HDS spectrum we find the star to be enriched in C ([C/Fe]_1D ~ +1.4) and O ([O/Fe]_1D ~ +1.8). With the…

Moderately r-process-enriched stars (r-I) are at least four times as common as those that are greatly enriched in r-process elements (r-II), and the abundances in their atmospheres are important tools for obtaining a better understanding of…

Solar and Stellar Astrophysics · Physics 2015-06-19 C. Siqueira-Mello , V. Hill , B. Barbuy , M. Spite , F. Spite , T. C. Beers , E. Caffau , P. Bonifacio , R. Cayrel , P. François , H. Schatz , S. Wanajo

The chemical evolution of neutron capture elements in the Milky Way is still a matter of debate. Although more and more studies investigate their chemical behaviour, there is still a lack of a significant large sample of abundances of a key…

Solar and Stellar Astrophysics · Physics 2024-08-30 G. Contursi , P. de Laverny , A. Recio-Blanco , M. Molero , E. Spitoni , F. Matteucci , S. Cristallo