Dependence of r-process Yields on the Progenitor Masses of Type II Supernovae

2003 ◽  
pp. 174-175
Author(s):  
Shinya Wanajo ◽  
Kaori Otsuki ◽  
Toshitaka Kajino ◽  
Yuhri Ishimaru
Keyword(s):  
Type Ii ◽  
R Process

Astrophysical conditions for an r-process in the high-entropy wind scenario of type II supernovae

2005 ◽  
Vol 758 ◽  
pp. 631-634 ◽  
Author(s):  
K. Farouqi ◽  
C. Freiburghaus ◽  
K.-L. Kratz ◽  
B. Pfeiffer ◽  
T. Rauscher ◽  
...  
Keyword(s):  
Type Ii ◽  
High Entropy ◽  
R Process

scholarly journals Nucleosynthesis of light trans-Fe isotopes in ccSNe: Implications from presolar SiC-X grains

2020 ◽  
Vol 227 ◽  
pp. 01009
Author(s):  
Waheed Akram ◽  
Khalil Farouqi ◽  
Oliver Hallmann ◽  
Karl-Ludwig Kratz
Keyword(s):  
Charged Particle ◽  
Massive Stars ◽  
Parameter Study ◽  
Type Ii ◽  
High Entropy ◽  
Abundance Estimates ◽  
Fe Isotopes ◽  
Type Ia ◽  
R Process ◽  
Low Entropy

This contribution presents an extension of our r-process parameter study within the high-entropy-wind (HEW) scenario of corecollapse supernovae (ccSNe). One of the primary aims of this study was to obtain indications for the production of classical p-, s- and r-isotopes of the light trans-Fe elements in the Solar System (S.S.). Here, we focus on the nucleosynthesis origin of the anomalous isotopic compositions of Zr, Mo and Ru in presolar SiC X-grains (SNe grains). In contrast to the interpretation of other groups, we show that these grains do not represent the signatures of a ‘clean’ stellar scenario, but rather, are mixtures of an exotic nucleosynthesis component and S.S. material. We further confirm the results of our earlier studies whereby sizeable amounts of all stable p-, s- and r-isotopes of Zr, Mo and Ru can be co-produced by moderately neutron-rich ejecta of the low-entropy, charged-particle scenario of ccSNe (type II). The synthesis of these isotopes through a ‘primary’ production mode provides further means to revise the abundance estimates of the light trans-Fe elements from so far favoured ‘secondary’ scenarios like Type Ia SNe or neutron-bursts in exploding massive stars.

scholarly journals Co-Production of Light p-, s- and r-Process Isotopes in the High-Entropy Wind of Type II Supernovae

2009 ◽  
Vol 26 (3) ◽  
pp. 194-202 ◽  
Author(s):  
K. Farouqi ◽  
K.-L. Kratz ◽  
B. Pfeiffer
Keyword(s):  
Stable Isotopes ◽  
Charged Particle ◽  
Solar System ◽  
Large Scale ◽  
Type Ii ◽  
Isotopic Abundance ◽  
Isotopic Chain ◽  
High Entropy ◽  
R Process ◽  
Particle Process

AbstractWe have performed large-scale nucleosynthesis calculations within the high-entropy-wind (HEW) scenario of Type II supernovae. The primary aim was to constrain the conditions for the production of the classical ‘p-only’ isotopes of the light trans-Fe elements. We find, however, that for electron fractions in the range 0.458 ≤ Ye ≤ 0.478, sizeable abundances of p-, s- and r-process nuclei between 64Zn and 98Ru are coproduced in the HEW at low entropies (S ≤ 100) by a primary charged-particle process after an α-rich freezeout. With the above Ye–S correlation, most of the predicted isotopic abundance ratios within a given element, e.g. 64Zn(p)/70Zn(r) or 92Mo(p)/94Mo(p), as well as of neighboring elements, e.g. 70Ge(s + p)/74Se(p) or 74Se(p)/78Kr(p) agree with the observed Solar-System ratios. Taking the Mo isotopic chain as a particularly challenging example, we show that our HEW model can account for the production of all 7 stable isotopes, from ‘p-only’ 92Mo, via ‘s-only’ 96Mo up to ‘r-only’ 100Mo. Furthermore, our model is able to reproduce the isotopic composition of Mo in presolar SiC X-grains.

r-process in Type II supernovae and the role of direct capture

2010 ◽  
Author(s):  
K. Otsuki ◽  
A. Burrows ◽  
G. Martinez-Pinedo ◽  
S. Typel ◽  
K. Langanke ◽  
...  
Keyword(s):  
Type Ii ◽  
Direct Capture ◽  
R Process

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 S-Process Deficiencies in Low-Mass Supergiant Variables

1989 ◽  
Vol 106 ◽  
pp. 154-154
Author(s):  
Howard E. Bond ◽  
R. Earle Luck
Keyword(s):  
Variable Stars ◽  
Elemental Abundance ◽  
Type Ii ◽  
Hydrogen Burning ◽  
Halo Stars ◽  
Low Mass ◽  
R Process ◽  
Nuclear Processing ◽  
Halo Population ◽  
Process Elements

We have carried out abundance analyses of four low-mass supergiant variable stars (the RV Tauri or RV Tau-like variables AI Cmi, RU Cen, and U Mon, and the Type II Cepheid Kappa Pav) and two Population I Cepheids (CO Aur and V378 Cen). We used model atmospheres in which hydrostatic equilibrium, plane-parallel geometry, and local thermodynamic equilibrium (LTE) were assumed. Discussion of the results, and of published analyses of additional low-mass variables, leads to the following conclusions. (1) The Population I Cepheids show normal, solar elemental abundance ratios (except for the CNO elements, which have been altered by hydrogen burning), lending some support to the validity of the above assumptions for analyses of luminous variable stars. (2) The low-mass variables show metallicities ranging from solar down to [Fe/H] values typical of thick-disk and, in a few cases, of halo stars. (3) Most low-mass variables show a systematic underabundance of the heavy s- and r-process elements. In a few cases this may indicate that the stars were initially of extremely low metal content, and are now hydrogen deficient. However, most of the variables do not appear to belong to the halo population, nor do they show other abundance patterns seen in halo stars. The origin of these underabundances, and their apparent confinement to luminous variables, are difficult to understand in the context of nuclear processing. (4) The heavy-element underabundances correlate with second ionization potential in a manner suggesting that they are non-LTE phenomenan arising from overionization by Lyman-continuum photons. Why a similar effect is not seen in Population I Cepheids is unclear, but may be related to their generally weaker hydrogen emission. (5) Several low-mass variables, including RU Cen and V553 Cen, show carbon enhancements and solar s-process abundances. Relative to the majority of the Type II variables, these stars are s-process enhanced, and we argue that they are related to the Ba II and CH stars.

NU-PROCESS IN EXOTIC MODELS

2010 ◽  
Vol 19 (08n10) ◽  
pp. 1731-1735
Author(s):  
L. PAULUCCI ◽  
J. E. HORVATH
Keyword(s):  
Nuclear Matter ◽  
Type Ii ◽  
Strange Matter ◽  
Physical Conditions ◽  
Proposed Model ◽  
R Process ◽  
Freeze Out

The exact physical conditions generating the abundances of r-elements in environments such as supernovae explosions are still under debate. We evaluated the characteristics expected for the neutrino wind in the proposed model of type-II supernova driven by conversion of nuclear matter to strange matter. Neutrinos will change the final abundance of elements after freeze out of r-process nucleosynthesis, specially those close to mass peaks.

scholarly journals R-Process nucleosynthesis in high entropy environment in explosion of supernova type II and neutron star formation

2012 ◽  
Vol 8 (S291) ◽  
pp. 352-352
Author(s):  
Rulee Baruah ◽  
Kalpana Duorah ◽  
H. L. Duorah
Keyword(s):  
Neutron Star ◽  
Supernova Explosion ◽  
Neutron Number ◽  
Iron Core ◽  
Type Ii ◽  
Fusion Reactions ◽  
Capture Process ◽  
High Entropy ◽  
Wave Forms ◽  
R Process

AbstractIt is generally acknowledged that Type II supernovae result from the collapse of iron core of a massive star which, at least in some cases, produces a neutron star. At this stage, the neutrinos are produced by neutronization which speeds up as collapse continues. During collapse an outward bound shock wave forms in the matter falling onto the nearly stationary core. The conditions behind the shock at 100 to 200 km are suitable for neutrino heating. This neutrino heating blows a hot bubble above the protoneutron star and is the most important source of energy for Supernova explosion. At this stage, we try to attain the r-process (rapid neutron capture process) path responsible for the production of heavy elements beyond iron, which are otherwise not possible to be formed by fusion reactions. The most interesting evolution occurs as temperature falls from 1010 K to 109 K. At these high temperature conditions, the critical fluids after fusion reactions are forbidden and transform into the respective atoms by r-process path which on beta decaying produce the ultimate elements of the periodic chart.Another astrophysical parameter needed for our analysis is neutron number density which we take to be greater than 1020 cm−3. With these, at different entropy environments, we assign the neutron binding energy that represents the r-process path in the chart of nuclides. Along the path, the experimental data of observed elements matches our calculated one. We find that an entropy of ~300 with Ye ≃ 0.45 can lead to a successful r-process. It produced heavy neutron-rich nuclei with A ≃ 80 – 240. Later ejecta are neutron-rich (Ye ≤ 0.5) and leaves behind a compact neutron star.

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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