scholarly journals Inhomogeneous Chemical Evolution of r-process Elements in the Galactic Halo

2017 ◽  
Author(s):  
Benjamin Wehmeyer ◽  
Marco Pignatari ◽  
Friedrich-Karl Thielemann
Keyword(s):  
Chemical Evolution ◽  
Galactic Halo ◽  
R Process ◽  
Process Elements

scholarly journals Inhomogeneous Chemical Evolution of r-Process Elements in the Galactic Halo

2019 ◽  
pp. 91-96
Author(s):  
Benjamin Wehmeyer ◽  
Carla Fröhlich ◽  
Marco Pignatari ◽  
Friedrich-Karl Thielemann
Keyword(s):  
Chemical Evolution ◽  
Galactic Halo ◽  
R Process ◽  
Process Elements

Distribution of R- and S-Process Elements in the Galactic Halo

1988 ◽  
Vol 132 ◽  
pp. 501-506
Author(s):  
C. Sneden ◽  
C. A. Pilachowski ◽  
K. K. Gilroy ◽  
J. J. Cowan
Keyword(s):  
Heavy Element ◽  
Galactic Halo ◽  
Low Noise ◽  
Heavy Elements ◽  
Process Synthesis ◽  
Element Abundances ◽  
Halo Stars ◽  
Abundance Patterns ◽  
R Process ◽  
Process Elements

Current observational results for the abundances of the very heavy elements (Z>30) in Population II halo stars are reviewed. New high resolution, low noise spectra of many of these extremely metal-poor stars reveal general consistency in their overall abundance patterns. Below Galactic metallicities of [Fe/H] Ã −2, all of the very heavy elements were manufactured almost exclusively in r-process synthesis events. However, there is considerable star-to-star scatter in the overall level of very heavy element abundances, indicating the influence of local supernovas on element production in the very early, unmixed Galactic halo. The s-process appears to contribute substantially to stellar abundances only in stars more metal-rich than [Fe/H] Ã −2.

scholarly journals The AMBRE Project: r-process elements in the Milky Way thin and thick discs

2018 ◽  
Vol 619 ◽  
pp. A143 ◽  
Author(s):  
G. Guiglion ◽  
P. de Laverny ◽  
A. Recio-Blanco ◽  
N. Prantzos
Keyword(s):  
Chemical Evolution ◽  
Milky Way ◽  
Element Abundances ◽  
Thick Disc ◽  
Thin Disc ◽  
Solar Metallicity ◽  
R Process ◽  
Process Elements ◽  
Process Element ◽  
The Eu

Context. The chemical evolution of neutron capture elements in the Milky Way disc is still a matter of debate. There is a lack of statistically significant catalogues of such element abundances, especially those of the r-process. Aims. We aim to understand the chemical evolution of r-process elements in Milky Way disc. We focus on three pure r-process elements Eu, Gd, and Dy. We also consider a pure s-process element, Ba, in order to disentangle the different nucleosynthesis processes. Methods. We take advantage of high-resolution FEROS, HARPS, and UVES spectra from the ESO archive in order to perform a homogeneous analysis on 6500 FGK Milky Way stars. The chemical analysis is performed thanks to the automatic optimization pipeline GAUGUIN. We present abundances of Ba (5057 stars), Eu (6268 stars), Gd (5431 stars), and Dy (5479 stars). Based on the [α/Fe] ratio determined previously by the AMBRE Project, we chemically characterize the thin and the thick discs, and a metal-rich α-rich population. Results. First, we find that the [Eu/Fe] ratio follows a continuous sequence from the thin disc to the thick disc as a function of the metallicity. Second, in thick disc stars, the [Eu/Ba] ratio is found to be constant, while the [Gd/Ba] and [Dy/Ba] ratios decrease as a function of the metallicity. These observations clearly indicate a different nucleosynthesis history in the thick disc between Eu and Gd–Dy. The [r/Fe] ratio in the thin disc is roughly around +0.1 dex at solar metallicity, which is not the case for Ba. We also find that the α-rich metal-rich stars are also enriched in r-process elements (like thick disc stars), but their [Ba/Fe] is very different from thick disc stars. Finally, we find that the [r/α] ratio tends to decrease with metallicity, indicating that supernovae of different properties probably contribute differently to the synthesis of r-process elements and α-elements. Conclusions. We provide average abundance trends for [Ba/Fe] and [Eu/Fe] with rather small dispersions, and for the first time for [Gd/Fe] and [Dy/Fe]. This data may help to constrain chemical evolution models of Milky Way r- and s-process elements and the yields of massive stars. We emphasize that including yields of neutron-star or black hole mergers is now crucial if we want to quantitatively compare observations to Galactic chemical evolution models.

scholarly journals Compact binary mergers as the origin of r-process elements in the Galactic halo

2014 ◽  
Author(s):  
Yuhri Ishimaru ◽  
Shinya Wanajo ◽  
Nikos Prantzos
Keyword(s):  
Galactic Halo ◽  
Compact Binary ◽  
Binary Mergers ◽  
R Process ◽  
Process Elements

scholarly journals Chemical Evolution of R-process Elements in the Hierarchical Galaxy Formation

2015 ◽  
Vol 11 (S317) ◽  
pp. 318-319
Author(s):  
Yutaka Komiya ◽  
Toshikazu Shigeyama
Keyword(s):  
Neutron Star ◽  
Chemical Evolution ◽  
Galaxy Formation ◽  
Milky Way ◽  
Galactic Chemical Evolution ◽  
Halo Stars ◽  
R Process ◽  
Process Elements ◽  
Milky Way Halo

AbstractThe main astronomical source of r-process elements has not yet been identified. One plausible site is neutron star mergers (NSMs). From the perspective of Galactic chemical evolution, however, it has been pointed out that the NSM scenario is incompatible with observations. Recently, Tsujimoto & Shigeyama (2014) pointed out that NSM ejecta can spread into much larger volume than ejecta from a supernova. We re-examine the chemical evolution of r-process elements under the NSM scenario considering this difference in propagation of the ejecta. We find that the NSM scenario can be compatible with the observed abundances of the Milky Way halo stars.

scholarly journals Stochastic Chemical Evolution of Sub-Halos and the Origin of r-Process Elements

2017 ◽  
Author(s):  
Takuya Ojima ◽  
Yuhri Ishimaru ◽  
Shinya Wanajo ◽  
Nikos Prantzos
Keyword(s):  
Chemical Evolution ◽  
R Process ◽  
Process Elements

scholarly journals The Yields of r-Process Elements and Chemical Evolution of the Galaxy

2006 ◽  
Vol 306 (1-2) ◽  
pp. 33-39 ◽  
Author(s):  
Zhe Chen ◽  
Jiang Zhang ◽  
YanPing Chen ◽  
WenYuan Cui ◽  
Bo Zhang
Keyword(s):  
Chemical Evolution ◽  
The Galaxy ◽  
R Process ◽  
Process Elements

scholarly journals Inhomogeneous chemical evolution of r-process elements

2016 ◽  
Author(s):  
B. Wehmeyer ◽  
M. Pignatari ◽  
F.-K. Thielemann
Keyword(s):  
Chemical Evolution ◽  
R Process ◽  
Process Elements

scholarly journals Chemical evolution of C-Zn and r-process elements produced by the first generation stars

2010 ◽  
Author(s):  
Yuhri Ishimaru ◽  
Shinya Wanajo ◽  
Nikos Prantzos
Keyword(s):  
Chemical Evolution ◽  
First Generation ◽  
R Process ◽  
Process Elements

scholarly journals Neutron star mergers as sites of r-process nucleosynthesis and short gamma-ray bursts

2018 ◽  
Vol 27 (13) ◽  
pp. 1842005 ◽  
Author(s):  
Kenta Hotokezaka ◽  
Paz Beniamini ◽  
Tsvi Piran
Keyword(s):  
Neutron Star ◽  
Chemical Evolution ◽  
Near Infrared ◽  
Gamma Ray ◽  
Ultra Violet ◽  
Gamma Ray Bursts ◽  
Galactic Model ◽  
Multi Wavelength ◽  
R Process ◽  
Process Elements

Neutron star mergers have been long considered as promising sites of heavy [Formula: see text]-process nucleosynthesis. We overview the observational evidence supporting this scenario including: the total amount of [Formula: see text]-process elements in the galaxy, extreme metal-poor stars, geological radioactive elemental abundances, dwarf galaxies and short gamma-ray bursts (sGRBs). Recently, the advanced LIGO and Virgo observatories discovered a gravitational-wave signal of a neutron star merger, GW170817, as well as accompanying multi-wavelength electromagnetic (EM) counterparts. The ultra-violet, optical and near infrared (n/R) observations point to [Formula: see text]-process elements that have been synthesized in the merger ejecta. The rate and ejected mass inferred from GW170817 and the EM counterparts are consistent with other observations. We however, find that, within the simple one zone chemical evolution models (based on merger rates with reasonable delay time distributions as expected from evolutionary models, or from observations of sGRBs), it is difficult to reconcile the current observations of the Eu abundance history of galactic stars for [Fe/H] [Formula: see text]. This implies that to account for the role of mergers in the galactic chemical evolution, we need a galactic model with multiple populations that have different spatial distributions and/or varying formation rates.

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