Reaction rate sensitivity of Ti-44 production in massive stars and implications of a thick target yield measurement of Ca-40(alpha, gamma)Ti-44

R. D. Hoffman, S. A. Sheets, J. T. Burke, N. D. Scielzo, T. Rauscher, E. B. Norman, S. Tumey, T. A. Brown, P. G. Grant, A. M. Hurst, L. Phair, M. A. Stoyer, T. Wooddy, J. L. Fisker, D. Bleuel

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Abstract

We evaluate two dominant nuclear reaction rates and their uncertainties that affect Ti-44 production in explosive nucleosynthesis. Experimentally we develop thick target yields for the Ca-40(alpha, gamma)Ti-44 reaction at E alpha = 4.13, 4.54, and 5.36 MeV using gamma-ray spectroscopy. At the highest beam energy, we also performed an activation measurement which agrees with the thick target result. From the measured yields a stellar reaction rate was developed that is smaller than current statistical-model calculations and recent experimental results, which would suggest lower Ti-44 production in scenarios for the alpha-rich freezeout. Special attention has been paid to assessing realistic uncertainties of stellar reaction rates produced from a combination of experimental and theoretical cross sections. With such methods, we also develop a re-evaluation of the Ti-44(alpha, p)V-47 reaction rate. Using these two rates we carry out a sensitivity survey of Ti-44 synthesis in eight expansions representing peak temperature and density conditions drawn from a suite of recent supernova explosion models. Our results suggest that the current uncertainty in these two reaction rates could lead to as large an uncertainty in Ti-44 synthesis as that produced by different treatments of stellar physics.

Original languageEnglish
Pages (from-to)1383-1399
Number of pages17
JournalThe Astrophysical Journal
Volume715
Issue number2
DOIs
Publication statusPublished - 1 Jun 2010

Keywords

  • NUCLEAR
  • THERMONUCLEAR REACTION-RATES
  • CASSIOPEIA-A
  • STATISTICAL-MODEL CALCULATIONS
  • supernovae: general
  • CONSTRAINTS
  • CROSS-SECTIONS
  • SUPERNOVAE
  • ASTROPHYSICAL REACTION-RATES
  • nuclear reactions, nucleosynthesis, abundances
  • GAMMA-RAY
  • NUCLEOSYNTHESIS

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