scholarly journals Novel techniques for constraining neutron-capture rates relevant for r-process heavy-element nucleosynthesis

2019 ◽  
Vol 107 ◽  
pp. 69-108 ◽  
Author(s):  
A.C. Larsen ◽  
A. Spyrou ◽  
S.N. Liddick ◽  
M. Guttormsen
Keyword(s):  
Neutron Capture ◽  
Heavy Element ◽  
R Process ◽  
Capture Rates

scholarly journals Sensitivity studies for the weak r process: neutron capture rates

AIP Advances ◽  
2014 ◽  
Vol 4 (4) ◽  
pp. 041008 ◽  
Author(s):  
R. Surman ◽  
M. Mumpower ◽  
R. Sinclair ◽  
K. L. Jones ◽  
W. R. Hix ◽  
...  
Keyword(s):  
Neutron Capture ◽  
Sensitivity Studies ◽  
R Process ◽  
Capture Rates

Heavy Element Abundances in the Magellanic Clouds

1991 ◽  
Vol 9 (1) ◽  
pp. 82-83 ◽  
Author(s):  
Stephen C. Russell
Keyword(s):  
Neutron Capture ◽  
Heavy Element ◽  
Magellanic Clouds ◽  
Element Abundances ◽  
R Process

AbstractThis paper presents a brief discussion of the apparent underdepletion of the heavy neutron-capture elements (elements heavier than Ba), compared with Fe in the Magellanic Clouds. The s-process appears to have been only effective in forming elements in the light neutron-capture group (Sr, Y, Zr) in the Magellanic Clouds, but to have much reduced effectiveness in forming the heavy neutron-capture group. The abundances of the elements heavier than Ba have a distribution that indicates that they were produced by the r-process alone.

scholarly journals NEUTRON CAPTURE RATES AND r-PROCESS NUCLEOSYNTHESIS

2013 ◽  
Author(s):  
R. A. SURMAN ◽  
M. R. MUMPOWER ◽  
G. C. MCLAUGHLIN ◽  
R. SINCLAIR ◽  
W. R. HIX ◽  
...  
Keyword(s):  
Neutron Capture ◽  
R Process ◽  
Capture Rates

scholarly journals Chemical Evolution and Extremely Metal-Poor Stars

1998 ◽  
Vol 11 (1) ◽  
pp. 49-52
Author(s):  
Andrew McWilliam
Keyword(s):  
Neutron Capture ◽  
Heavy Element ◽  
Massive Stars ◽  
Small Sample ◽  
Heavy Elements ◽  
High Mass ◽  
Type Ii ◽  
Element Abundances ◽  
Halo Stars ◽  
R Process

Early abundance studies (e.g. Pagel 1968) showed that neutron-capture heavy elements (Z > 30) are present in halo stars, but deficient relative iron. Truran (1981) argued that at low [Fe/H] the chemical enrichment time scale was shorter than the lifetime of low-mass AGB progenitors, which are the main source of solar system heavy elements. He proposed that in the halo the heavy elements were produced by high mass stars, in type II supernova events (SNII), by rapid neutron capture nucleosynthesis (the r-process). Spite & Spite (1978) investigated the trend of heavy element abundances with metallicity, from a small sample of halo stars. They found that at [Fe/H]~ -1.5 the halo [heavy element/Fe] ratio is approximately solar; but at lower [Fe/H] there is a roughly linear decrease of [heavy element/Fe] with declining [Fe/H]. Subsequent observations confirmed the general trend of heavy elements in the halo: [M/Fe]~0 down to [Fe/H]~ -2, followed by a linear decline in [M/Fe] to lower [Fe/H] (e.g. Gilroy et al 1988, Lambert 1987). Additional evidence for the role of SNII in halo heavy element synthesis comes from the trend of [Eu/Fe] with [Fe/H]. Europium is an almost pure r-process element (Käppeler et al. 1989) and its abundance trend with metallicity is similar to the α element trend (e.g. O and Mg made in massive stars). The element ratios show an increase in [M/Fe] as [Fe/H] decreases from 0 to —1; below this point [Eu/Fe] and [α/Fe] remain constant at ~+0.3 dex. For α elements this behavior is thought to be due to the change in the relative contributions from type II SN and type la SN in the disk and halo (Tinsley 1979). The trend for Eu also indicates production by massive stars (e.g. SNII). Near [Fe/H]~ -2.5 Eu appears to decline relative to [Fe/H] (like other heavy elements, but unlike the α elements). This abundance trend has been used to constrain the numerous proposed astrophysical sites of the r-process (e.g. Mathews & Cowan 1990).

scholarly journals Heavy Element Nucleosynthesis

2018 ◽  
Vol 184 ◽  
pp. 01007
Author(s):  
Mounib F. El Eid
Keyword(s):  
Chemical Evolution ◽  
Neutron Capture ◽  
Heavy Element ◽  
Slow Neutron ◽  
Heavy Elements ◽  
Galactic Chemical Evolution ◽  
Physical Processes ◽  
The Galaxy ◽  
R Process

This contribution deals with the important subject of the nucleosynthesis of heavy elements in the Galaxy. After an overview of several observational features, the physical processes responsible mainly for the formation of heavy elements will be described and linked to possible stellar sites and to galactic chemical evolution. In particular, we focus on the neutron-capture processes, namely the s-process (slow neutron capture) and the r-process (rapid neutron capture) and discuss some problems in connection with their sites and their outcome. The aim is to give a brief overview on the exciting subject of the heavy element nucleosynthesis in the Galaxy, emphasizing its importance to trace the galactic chemical evolution and illustrating the challenge of this subject.

Neutron capture rates in the r-process - The role of direct radiative capture

1983 ◽  
Vol 270 ◽  
pp. 740 ◽  
Author(s):  
G. J. Mathews ◽  
A. Mengoni ◽  
F.-K. Thielemann ◽  
W. A. Fowler
Keyword(s):  
Neutron Capture ◽  
Radiative Capture ◽  
R Process ◽  
Capture Rates

scholarly journals Novel Techniques for Constraining Neutron-capture Rates relevant to Heavy-element Nucleosynthesis

2017 ◽  
Author(s):  
Anne-Cecilie Larsen ◽  
Artemis Spyrou ◽  
Sean Liddick ◽  
Magne Guttormsen ◽  
Vetle Wegner Ingeberg ◽  
...  
Keyword(s):  
Neutron Capture ◽  
Heavy Element ◽  
Capture Rates

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.

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