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Vetterli, M. C.; Häusser, O.; Abegg, R.; Alford, W.P.; Celler, Anna; Frekers, D.; Helmer, R. L.; Henderson, R.; Hicks, K.; Jackson, K. P.; Jeppesen, R. H.; Miller, C. A.; Raywood, K.; Yen, S.

doi:10.1103/physrevc.40.559

Cited by 115 publications

(101 citation statements)

References 21 publications

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“…FFN estimated their rates based upon the presence of a single Gamow-Teller (GT) resonance which they derived on the basis of the independent particle model, supplemented, where available, by experimental data for low-lying transitions. However, recent experimental data on the GT distributions in nuclei (Alford et al 1990 ;Vetterli et al 1989 ;Alford et al 1993 ;El-Kateb et al 1994 ; Williams et al 1990) shows a quenching of the total GT strength compared to the independent-particle model value. More importantly, the data also show a fragmentation of the GT strength over many states in the daughter nucleus.…”

Section: The New Ratesmentioning

confidence: 99%

Presupernova Evolution with Improved Rates for Weak Interactions

Heger

Woosley

Martı́nez-Pinedo

et al. 2001

ApJ

209

228

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Recent shell-model calculations of weak-interaction rates for nuclei in the mass range A \ 45È65 have resulted in substantial revisions to the hitherto standard set of Fuller, Fowler, & Newman (FFN). In particular, key electron-capture rates, such as that for 60Co, are much smaller. We consider here the e †ects of these revised rates on the presupernova (postÈoxygen burning) evolution of massive stars in the mass range 11È40Moreover, we include, for the Ðrst time in models by our group, the e †ects of M _ . modern rates for beta decay in addition to electron capture and positron emission. Stars of 15, 25, and 40 are examined in detail using both the full FFN rate set and the revised rates. An additional M _ Ðnely spaced (in mass) grid of 34 models is also calculated in order to give the systematics of iron core and silicon core masses. Values for the central electron mole number at the time of iron core collapse in the new models are typically larger, by than those of Woosley & Weaver, with a *Y e \ 0.005È0.015, tendency for the more massive models to display larger di †erences. About half of this change is a consequence of including beta decay ; the other half, the result of the smaller rates for electron capture. Unlike what might be expected solely on basis of the larger values, the new iron core masses are systemati-Y e cally smaller owing to a decrease in the entropy in the outer iron core. The changes in iron core mass range from zero to 0.1 (larger changes for high-mass stars). It would be erroneous however to esti-M _ mate the facility of exploding these new models based solely upon their iron core mass since the entire core structure is altered and the density change is not so di †erent as the adjustments in composition might suggest. We also observe, as predicted by Aufderheide et al., a tendency toward beta equilibrium just prior to the collapse of the core, and the subsequent loss of that equilibrium as core collapse proceeds. This tendency is more pronounced in the 15 model than in the heavier stars. We discuss the M _ key weak reaction rates, both beta decay and electron capture, responsible for the evolution of and Y e make suggestions for future measurements.

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Section: The New Ratesmentioning

confidence: 99%

Presupernova Evolution with Improved Rates for Weak Interactions

Heger

Woosley

Martı́nez-Pinedo

et al. 2001

ApJ

209

228

View full text Add to dashboard Cite

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“…After experimental (n,p) data clearly indicated that the Gamow-Teller strength is not only quenched (usually by more than a factor 2 compared to the independent particle model), but also fragmented over several states at modest excitation energies in the daughter nucleus [5][6][7][8][9], the need for an improved theoretical description has soon been realized [10][11][12]. These studies have been performed within the conventional shell model diagonalization approach, however, in strongly restricted model spaces and with residual interactions, which turned out to neither reproduce the quenching nor the position of the GT strength sufficiently well.…”

Section: Introductionmentioning

confidence: 99%

Supernova electron capture rates for 55Co and 56Ni

Langanke

Martı́nez-Pinedo

1998

Physics Letters B

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We have calculated the Gamow-Teller strength distributions for the ground states and first excited states in 55 Co and 56 Ni. These calculations have been performed by shell model diagonalization in the pf shell using the KB3 interaction. The Gamow-Teller distributions are used to calculate the electron capture rates for typical presupernova conditions. Our 55 Co rate is noticeably smaller than the presently adopted rate as it is dominated by weak low-lying transitions rather than the strong Gamow-Teller (GT) resonance which is located at a higher excitation energy in the daughter than usually parametrized. Although our 56 Ni rate agrees with the presently adopted rate, we do not confirm the conventional parametrization of the GT centroid. Our results support general trends suggested on the basis of shell model Monte Carlo calculations.

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“…Thus it follows that both, stellar electron capture and beta decay, are very sensitive to the distribution of the GT + strength (in this direction a proton is changed into a neutron). In the last decade, GT + strength distributions on nuclei in the mass range A = 50 − 65 have been studied experimentally via (n,p) charge-exchange reactions at forward angles and the experimental data [3][4][5][6][7] show that, in contrast to the independent particle model, the total GT + strength is quenched and fragmented over many final states in the daughter nucleus caused by residual nucleon-nucleon correlations. Importantly for the stellar weak reaction rates, the data indicate a systematic misplacement of the GT centroid adopted in the FFN parametrization.…”

mentioning

confidence: 99%

Shell-model calculations of stellar weak interaction rates. I. Gamow-Teller distributions and spectra of nuclei in the mass range A = 45–65

Langanke²,

et al. 1999

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Shell model calculations of stellar weak interaction rates: I. Gamow-Teller distributions and spectra of nuclei in the mass range A = 45 − 65 Electron capture and beta-decay rates on nuclei in the mass range A = 45 − 65 play an important role in many astrophysical environments. The determination of these rates by large-scale shell model calculations is desirable, but it requires to reproduce the Gamow-Teller strength distributions and spectra of the pf shell nuclei. We show in this paper that large-scale shell model calculations, employing a slightly monopole-corrected version of the wellknown KB3 interaction, fulfill these necessary requirements. In particular, our calculations reproduce the experimentally available GT+ and GT− strength distributions and the nuclear halflives, and describe the nuclear spectra appropriately.

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Gamow-Teller strength deduced from charge exchange reactions onFe54at 300 MeV

Cited by 115 publications

References 21 publications

Presupernova Evolution with Improved Rates for Weak Interactions

Presupernova Evolution with Improved Rates for Weak Interactions

Supernova electron capture rates for 55Co and 56Ni

Shell-model calculations of stellar weak interaction rates. I. Gamow-Teller distributions and spectra of nuclei in the mass range A = 45–65

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