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Title: Barium from a mini r-process in supernovae

Abstract

The relative yields of the A = 134, 135, 136, 137, and 138 isobars have been calculated with an approximate model for the mini r-process which is thought to occur in the O, Ne-rich shell of a massive star during explosive burning. Neutron dose Phi/sub n/ is the primary parameter of the calculations. The isotopic anomaly of Ba in the EK-1-4-1 inclusion of the Allende meteorite demands comparable yields at A = 135 and A = 137 (McCulloch and Wasserburg). Near-equal yields occur in the calculations for Phi/sub n/ roughly-equal1.5 x 10/sup -7/ mole cm/sup -3/ s and for Phi/sub n/ > or approx. =10/sup -6/ mole cm/sup -3/ s. For the small neutron dose, the A = 137 and A = 138 yields are near-equal which implies an excess of /sup 138/Ba in EK-1-4-1 of only 1--2 parts in 10/sup 4/. The small neutron dose is close to that for which the isotopically anomalous r-Xe in carbonaceous chondrites is formed by the same process (Heymann and Dziczkaniec). For the large neutron dose, the A = 138 yield is an order of magnitude larger than the A = 135 and A = 137 yields, which is difficult to accept. Thus,more » the dilemma of the alarmingly large /sup 138/Ba yield from an s-enhanced seed, noted by Lee et al., is resolved, provided that the neutron dose of the mini r-process in the O, Ne-rich zone of a supernova is an order of magnitude smaller than the doses typically deduced for standard explosive carbon burning. Implications for Nd and Sm anomalies in the EK-1-4-1 inclusion are discussed. The calculated /sup 136/Ba is not fully consistent with observations. This could be due either to holdup of the decay of /sup 135/Xe to /sup 135/Ba at /sup 135/Cs, and/or to substantial reworking of /sup 135/Xe to /sup 134/Xe during the cooling phase of the mini r-process.« less

Authors:
Publication Date:
OSTI Identifier:
5984434
Resource Type:
Journal Article
Journal Name:
Astrophys. J.; (United States)
Additional Journal Information:
Journal Volume: 267:2
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; BARIUM ISOTOPES; NUCLEOSYNTHESIS; SUPERNOVAE; R PROCESS; ABUNDANCE; CAPTURE; ISOTOPE RATIO; METEORITES; NEUTRON REACTIONS; NEUTRONS; XENON ISOTOPES; ALKALINE EARTH ISOTOPES; BARYON REACTIONS; BARYONS; ELEMENTARY PARTICLES; ERUPTIVE VARIABLE STARS; FERMIONS; HADRON REACTIONS; HADRONS; ISOTOPES; NUCLEAR REACTIONS; NUCLEON REACTIONS; NUCLEONS; STAR EVOLUTION; STARS; VARIABLE STARS; 640102* - Astrophysics & Cosmology- Stars & Quasi-Stellar, Radio & X-Ray Sources

Citation Formats

Heymann, D. Barium from a mini r-process in supernovae. United States: N. p., 1983. Web. doi:10.1086/160912.
Heymann, D. Barium from a mini r-process in supernovae. United States. doi:10.1086/160912.
Heymann, D. Fri . "Barium from a mini r-process in supernovae". United States. doi:10.1086/160912.
@article{osti_5984434,
title = {Barium from a mini r-process in supernovae},
author = {Heymann, D.},
abstractNote = {The relative yields of the A = 134, 135, 136, 137, and 138 isobars have been calculated with an approximate model for the mini r-process which is thought to occur in the O, Ne-rich shell of a massive star during explosive burning. Neutron dose Phi/sub n/ is the primary parameter of the calculations. The isotopic anomaly of Ba in the EK-1-4-1 inclusion of the Allende meteorite demands comparable yields at A = 135 and A = 137 (McCulloch and Wasserburg). Near-equal yields occur in the calculations for Phi/sub n/ roughly-equal1.5 x 10/sup -7/ mole cm/sup -3/ s and for Phi/sub n/ > or approx. =10/sup -6/ mole cm/sup -3/ s. For the small neutron dose, the A = 137 and A = 138 yields are near-equal which implies an excess of /sup 138/Ba in EK-1-4-1 of only 1--2 parts in 10/sup 4/. The small neutron dose is close to that for which the isotopically anomalous r-Xe in carbonaceous chondrites is formed by the same process (Heymann and Dziczkaniec). For the large neutron dose, the A = 138 yield is an order of magnitude larger than the A = 135 and A = 137 yields, which is difficult to accept. Thus, the dilemma of the alarmingly large /sup 138/Ba yield from an s-enhanced seed, noted by Lee et al., is resolved, provided that the neutron dose of the mini r-process in the O, Ne-rich zone of a supernova is an order of magnitude smaller than the doses typically deduced for standard explosive carbon burning. Implications for Nd and Sm anomalies in the EK-1-4-1 inclusion are discussed. The calculated /sup 136/Ba is not fully consistent with observations. This could be due either to holdup of the decay of /sup 135/Xe to /sup 135/Ba at /sup 135/Cs, and/or to substantial reworking of /sup 135/Xe to /sup 134/Xe during the cooling phase of the mini r-process.},
doi = {10.1086/160912},
journal = {Astrophys. J.; (United States)},
number = ,
volume = 267:2,
place = {United States},
year = {1983},
month = {4}
}