IMPACT OF A REVISED {sup 25}Mg(p, {gamma}){sup 26}Al REACTION RATE ON THE OPERATION OF THE Mg-Al CYCLE

Journal Article · Fri Feb 15 00:00:00 EST 2013 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/763/2/100· OSTI ID:22167129

Straniero, O.; Cristallo, S. ^[1]; Imbriani, G.; DiLeva, A.; Limata, B. ^[2]; Strieder, F. ^[3]; Bemmerer, D. ^[4]; Broggini, C.; Caciolli, A. ^[5]; Corvisiero, P.; Costantini, H.; Lemut, A. ^[6]; Formicola, A.; Gustavino, C.; Junker, M. ^[7]; Elekes, Z.; Fueloep, Zs.; Gyuerky, Gy. ^[8]; Gervino, G. ^[9]; others, and

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1. INAF-Osservatorio Astronomico di Collurania, Teramo (Italy)
2. INFN Sezione di Napoli, Napoli (Italy)
3. Institut fuer Experimentalphysik, Ruhr-Universitaet Bochum, Bochum (Germany)
4. Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400 (Germany)
5. Istituto Nazionale di Fisica Nucleare (INFN), Sezione di Padova, via Marzolo 8, I-35131 Padova (Italy)
6. Universita di Genova and INFN Sezione di Genova, Genova (Italy)
7. INFN, Laboratori Nazionali del Gran Sasso (LNGS), Assergi (AQ) (Italy)
8. Institute of Nuclear Research (ATOMKI), Debrecen (Hungary)
9. Dipartimento di Fisica Universita di Torino and INFN Sezione di Torino, Torino (Italy)

Proton captures on Mg isotopes play an important role in the Mg-Al cycle active in stellar H-burning regions. In particular, low-energy nuclear resonances in the {sup 25}Mg(p, {gamma}){sup 26}Al reaction affect the production of radioactive {sup 26}Al{sup gs} as well as the resulting Mg/Al abundance ratio. Reliable estimations of these quantities require precise measurements of the strengths of low-energy resonances. Based on a new experimental study performed at the Laboratory for Underground Nuclear Astrophysics, we provide revised rates of the {sup 25}Mg(p, {gamma}){sup 26}Al{sup gs} and the {sup 25}Mg(p, {gamma}){sup 26}Al {sup m} reactions with corresponding uncertainties. In the temperature range 50-150 MK, the new recommended rate of {sup 26}Al {sup m} production is up to five times higher than previously assumed. In addition, at T = 100 MK, the revised total reaction rate is a factor of two higher. Note that this is the range of temperature at which the Mg-Al cycle operates in a H-burning zone. The effects of this revision are discussed. Due to the significantly larger {sup 25}Mg(p, {gamma}){sup 26}Al {sup m} rate, the estimated production of {sup 26}Al{sup gs} in H-burning regions is less efficient than previously obtained. As a result, the new rates should imply a smaller contribution from Wolf-Rayet stars to the galactic {sup 26}Al budget. Similarly, we show that the asymptotic giant branch (AGB) extra-mixing scenario does not appear able to explain the most extreme values of {sup 26}Al/{sup 27}Al, i.e., >10{sup -2}, found in some O-rich presolar grains. Finally, the substantial increase of the total reaction rate makes the hypothesis of self-pollution by massive AGBs a more robust explanation for the Mg-Al anticorrelation observed in globular-cluster stars.

• OSTI ID: 22167129
• Journal Information: Astrophysical Journal, Vol. 763, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ABUNDANCE
ALUMINIUM 26
ALUMINIUM 27
ASTROPHYSICS
ASYMPTOTIC SOLUTIONS
MAGNESIUM 25
NUCLEAR REACTIONS
NUCLEOSYNTHESIS
PROTONS
REACTION KINETICS
STAR CLUSTERS
TEMPERATURE RANGE
WOLF-RAYET STARS