Status of the Mg24(α,γ)Si28 reaction rate at stellar temperatures

Abstract

Background: The 24 Mg(α, γ) 28 Si reaction influences the production of magnesium and silicon isotopes during carbon burning and is one of eight reaction rates found to significantly impact the shape of calculated X-ray burst light curves. The reaction rate is based on measured resonance strengths and known properties of levels in 28 Si. Purpose: It is necessary to update the astrophysical reaction rate for 24 Mg(α, γ) 28 Si incorporating recent modifications to the nuclear level data for 28 Si, and to determine if any additional as-yet unobserved resonances could contribute to the 24 Mg(α, γ) 28 Si reaction rate. Methods: The reaction rate has been recalculated incorporating updated level assignments from 28 Si(α, α ′) 28 Si data using the RatesMC Monte-Carlo code. Evidence from the 28 Si(p, p ′) 28 Si reaction suggests that there are no further known resonances which could increase the reaction rate at astrophysically important temperatures, though some resonances do not yet have measured resonance strengths. Results: The reaction rate is substantially unchanged from previously calculated rates, especially at astrophysically important temperatures. However, the reaction rate is now constrained to better than 20% across the astrophysically-relevant energy range, with 95% confidence. Calculations of the X-ray burst lightcurve show no appreciable variations when varying the reaction rate within the uncertainty from the Monte-Carlo calculations. Conclusion: The 24 Mg(α, γ) 28 Si reaction rate, at temperatures relevant to carbon burning and Type I X-ray bursts, is well constrained by the available experimental data. This removes one reaction from the list of eight previously found to cause variations in X-ray burst light-curve calculations.

Charged-particle branching ratios above the neutron threshold in F19 : Constraining N15 production in core-collapse supern

“…In contrast, proton inelastic-scattering reactions at the energies used in the experiments described in this paper are not selective [28][29][30][31]. Therefore, unlike the previous resonance-reaction experimental studies of 19 F, we should populate most or all of the states present.…”

“…Some states listed in Table I at E x = 10.469 and 10.5656 MeV are not used in the fitting of the Q3D data. This could be because these states are not populated in the present reaction, which is unlikely given the non-selective nature of the (p, p ′ ) reaction at low energies [31], or because these states correspond to other known states which have been reported in different reactions. Other factors, such as revisions to the masses (and therefore particle thresholds), hinder the consistent identification of states between different experiments and may help to explain the discrepancies in the number and energy of the reported states.…”

Quadrupole properties of the eight $SU(3)$ algebras in $(sdgi)$ space

“…Going beyond the introduction of SU (3) in SM by Elliott [1,2] that is applicable only to light nuclei, the scope of SU (3) in nuclei is enlarged, spreading its applicability all across the periodic chart, by the developments in the pseudo-SU (3) model [3,4], SU (3) of fermion dynamical symmetry model [5], proxy-SU (3) model [6] and the Sp(6, R) model containing SU (3) [7][8][9] all within the shell model on one hand and by various extended IBM's such as IBM-2,3,4 [10], sdgIBM [11,12], sdpf IBM [13,14], IBFM (interacting boson-fermion model) and IBFFM (interacting boson-fermion-fermion model) [15][16][17] on the other. In addition, there are the algebraic cluster model [18,19] and many other models that employ SU (3) symmetry. A new paradigm in the applications of SU (3) in nuclei is the recent recognition that for nucleons in a given oscillator shell η, there will be multiple SU (3) algebras [20,21].…”

Understanding globular cluster abundances through nuclear reactions

“…This means that the states populated in 23 Na are not being populated in resonance scattering but in some other, rather non-selective, reaction mechanism which appears to be compound in nature. This reaction has been used to study a number of different isotopes already, such as 31 P, 28 Si, 27 Al, 24,26 Mg, 23 Na, and 19 F [10][11][12][13][14][15][16].…”