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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Constraints for stellar electron-capture rates on Kr-86 via the Kr-86(t, He-3 + gamma)Br-86 reaction and the implications for core-collapse supernovae

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Titus, E. R. [1, 2, 3] ; Ney, E. M. [4] ; Zegers, R. G. T. [1, 2, 3] ; Bazin, D. [1, 2] ; Belarge, J. [2] ; Bender, P. C. [5] ; Brown, B. A. [1, 2, 3] ; Campbell, C. M. [6] ; Elman, B. [1, 2] ; Engel, J. [4] ; Gade, A. [1, 2, 3] ; Gao, B. [7] ; Kwan, E. [2] ; Lipschutz, S. [1, 2, 3] ; Longfellow, B. [1, 2] ; Lunderberg, E. [1, 2] ; Mijatovic, T. [2] ; Noji, S. [2, 3] ; Pereira, J. [2, 3] ; Schmitt, J. [1, 2, 3] ; Sullivan, C. [1, 2, 3] ; Weisshaar, D. [2] ; Zamora, J. C. [8]
Total Authors: 23
[1] Michigan State Univ, Dept Phys & Astron, E Lansing, MI 48824 - USA
[2] Michigan State Univ, Natl Superconducting Cyclotron Lab, E Lansing, MI 48824 - USA
[3] Michigan State Univ, Joint Inst Nucl Astrophys, Ctr Evolut Elements, E Lansing, MI 48824 - USA
[4] Univ North Carolina Chapel Hill, Dept Phys & Astron, Chapel Hill, NC 27599 - USA
[5] Univ Massachusetts, Dept Phys, Lowell, MA 01854 - USA
[6] Lawrence Berkeley Natl Lab, Berkeley, CA 94720 - USA
[7] Chinese Acad Sci, Inst Modern Phys, Lanzhou 730000, Gansu - Peoples R China
[8] Univ Sao Paulo, Inst Fis, BR-05508090 Sao Paulo - Brazil
Total Affiliations: 8
Document type: Journal article
Source: Physical Review C; v. 100, n. 4 OCT 22 2019.
Web of Science Citations: 2

Background: In the late stages of stellar core collapse just prior to core bounce, electron captures on medium-heavy nuclei drive deleptonization. Therefore, simulations require the use of accurate reaction rates. Nuclei with neutron number near N = 50 above atomic number Z = 28 play an important role. Rates presently used in astrophysical simulations rely primarily on a relatively simple single-state approximation. In order to improve the accuracy of the astrophysical simulations, experimental data are needed to test the electron-capture rates and to guide the development of better theoretical models and astrophysical simulations. Purpose: The purpose of the present work was to measure the Gamow-Teller transition strength from Kr-86 to Br-86, to derive the stellar electron-capture rates based on the extracted strengths, and to compare the derived rates with rates based on shell-model and quasiparticle random-phase approximation (QRPA) Gamow-Teller strengths calculations, as well as the single-state approximation. An additional purpose was to test the impact of using improved electron-capture rates on the late evolution of core-collapse supernovae. Method: The Gamow-Teller strengths from Kr-86 were extracted from the Kr-86(t, He-3 + gamma) charge-exchange reaction at 115MeV/u. The electron-capture rates were calculated as a function of stellar density and temperature. Besides the case of Kr-86, the electron-capture rates based on the QRPA calculations were calculated for 78 additional isotopes near N = 50 above Z = 28. The impact of using these rates instead of those based on the single-state approximation is studied in a spherically symmetrical simulation of core collapse just prior to bounce. Results: The derived electron-capture rates on Kr-86 from the experimental Gamow-Teller strength distribution are much smaller than the rates estimated based on the single-state approximation. Rates based on Gamow-Teller strengths estimated in shell-model and QRPA calculations are more accurate. The core-collapse supernova simulation with electron-capture rates based on the QRPA calculations indicate a significant reduction in the deleptonization during the collapse phase. Conclusions: It is important to utilize microscopic theoretical models that are tested by experimental data to constrain and estimate Gamow-Teller strengths and derived electron-capture rates for nuclei near N = 50 that are inputs for astrophysical simulations of core-collapse supernovae and their multimessenger signals, such as the emission of neutrinos and gravitational waves. (AU)

FAPESP's process: 18/04965-4 - Study of structure and nuclear reactions induced by exotic nuclei using active targets
Grantee:Juan Carlos Zamora Cardona
Support Opportunities: Scholarships in Brazil - Post-Doctorate