Hydrogen burning of 24, 25, 26Mg in explosive carbon burning

Abstract

The absolute resonance strengths of the 24–26Mg(p, γ) 25–27Al reactions have been studied. The absolute values S c.m.=1.03 ± 0.11, 2.3 ± 0.2 and 2.2 ± 0.2 eV for the frequently used standard resonances at E p=823, 434 and 454 keV in the reactions 24–26Mg(p, γ) 25–27Al, respectively, have been determined. In addition, absolute values for use as standards were determined for the 684 keV 25Mg(p, γ) 26Al and 840 and 1966 keV 26Mg(p, γ) 27Al resonances. New relative values were determined for the strengths of the if 25Mg(p, γ) 26Al resonances at if E p = 0.3–1.7 MeV and the 26Mg(p, γ) 27Al resonances at E p = 0.3–2.1 MeV. The resonance energies and total widths obtained in the present work are also given. The branching ratios and angular distributions of the γ-rays used in the absolute strength determinations were obtained in the same set-up as the absolute strength measurement. Using the revised resonance strengths, the astrophysical reaction rates of hydrogen burning of 24–26Mg in explosive carbon burning in the stellar temperature region of T = (0.1–5.0) × 10 9 K are compared with Hauser-Feshbach calculations. The present reaction rates are also discussed in the frame of the MgAl cycle.