On the Sensitivity of Massive Star Nucleosynthesis and Evolution to Solar Abundances and to Uncertainties in Helium‐Burning Reaction Rates

Abstract

We explore the dependence of presupernova evolution and supernova nucleosynthesis yields on the uncertainties in helium-burning reaction rates. Using the revised solar abundances of Lodders for the initial stellar composition, instead of those of Anders and Grevesse, changes the supernova yields and limits the constraints that those yields place on the 12 C( ; ) 16 O reaction rate. The production factors of medium-weight elements (A ¼ 16Y40) were found to be in reasonable agreement with observed solar ratios within the current experimental uncertainties in the triple-reaction rate. Simultaneous variations by the same amount in both reaction rates or in either of them separately, however, can induce significant changes in the central 12 C abundance at core carbon ignition and in the mass of the supernova remnant. It therefore remains important to have experimental determinations of the helium-burning rates so that their ratio and absolute values are known with an accuracy of 10% or better.

Effects of the variation of fundamental constants on Population III stellar evolution

“…This effect comes from the higher central temperature and greater compactness at low δ NN . The same effect was found by other authors (Schlattl et al 2004;Tur et al 2007). As shown by these authors, this effect is expected to have an impact on the remnant mass and thus on the strength of the final explosion.…”

“…Rozental' (1988) argued that the synthesis of complex elements in stars (mainly the possibility of the triple α reaction (3α) as the origin of the production of 12 C) sets constraints on the values of the fine structure and strong coupling constants. There have been several studies on the sensitivity of carbon production to the underlying nuclear rates (Barrow 1987;Livio et al 1989;Fairbairn 1999;Csótó et al 2001;Oberhummer et al 2000Oberhummer et al , 2003Schlattl et al 2004;Tur et al 2007). The production of 12 C in stars requires a triple tuning: (i) the decay lifetime of 8 Be, of order 10 −16 s, is four orders of magnitude longer than the time for two α particles to scatter; (ii) an excited state of the carbon lies just above the energy of 8 Be + α and finally (iii) the energy level of 16 O at 7.1197 MeV is non resonant and below the energy of 12 C + α, at 7.1616 MeV, which ensures that most of the carbon synthesised is not destroyed by the capture of an α-particle.…”

The Compactness of Presupernova Stellar Cores

“…These energetic, merged oxygen, neon and carbon burning shells during the last hours of a massive star's life are a robust feature seen in many models of stars above about 15-20 M , both here and in previous studies (Woosley et al 1995;Tur et al 2007;Woosley & Heger 2007;Rauscher et al 2002). Their study would be an interesting, though perhaps challenging topic for three-dimensional simulation.…”

Effects of the variation of fundamental constants on Pop III stellar evolution

“…This effect is due to the higher central temperature and greater compactness at low δ NN . The same effect was found by other authors (Schlattl et al 2004;Tur et al 2007). As shown by these authors, this effect is expected to have an impact on the remnant mass and thus on the strength of the final explosion.…”

“…Rozental' (1988) argued that the synthesis of complex elements in stars (mainly the possibility of the 3α-reaction as the origin of the production of 12 C) sets constraints on the values of the fine structure and strong coupling constants. There have been several studies on the sensitivity of carbon production to the underlying nuclear rates (Livio et al 1989;Fairbairn 1999;Csoto et al 2001;Oberhummer et al 2000;Oberhummer et al 2003;Schlattl et al 2004;Tur et al 2007). The production of 12 C in stars requires a triple tuning: (i) the decay lifetime of 8 Be, of order 10 −16 s, is four orders of magnitude longer than the time for two α particles to scatter, (ii) an excited state of the carbon lies just above the energy of 8 Be + α and finally (iii) the energy level of 16 O at 7.1197 MeV is non resonant and below the energy of 12 C + α, at 7.1616 MeV, which ensures that most of the carbon synthesized is not destroyed by the capture of an α-particle.…”