First measurement of the 14N(<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si1.gif" overflow="scroll"><mml:mi mathvariant="normal">p</mml:mi><mml:mo>,</mml:mo><mml:mi>γ</mml:mi></mml:math>)15O cross section down to 70 keV

Lemut, A.; Bemmerer, D.; Confortola, F.; Bonetti, R.; Broggini, C.; Corvisiero, P.; Costantini, H.; Cruz, J.; Formicola, A.; Fülöp, Zsolt; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, György; Imbriani, G.; Jesus, A.P.; Junker, M.; Limata, B.; Menegazzo, R.; Prati, P.; Roca, V.; Rogalla, Detlef; Rolfs, C.; Romano, M.; Alvarez, C. Rossi; Schümann, F.; Somorjai, E.; Straniero, O.; Strieder, F.; Terrasi, F.; Trautvetter, H. P.

doi:10.1016/j.physletb.2006.02.021

Cited by 114 publications

(62 citation statements)

References 27 publications

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“…Also for E γ 3 MeV with proper shielding the γ -ray background has been found to be much lower than in comparable laboratories at the surface of the Earth [34]. The unique location of LUNA has enabled the study of several nuclear reactions of astrophysical importance [21,[35][36][37][38][39][40].…”

Section: Methodsmentioning

confidence: 99%

TheN14(p,γ)
Marta¹,
Formicola²,
Bemmerer³
et al. 2011
Phys. Rev. C
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The rate of the carbon-nitrogen-oxygen (CNO) cycle of hydrogen burning is controlled by the 14 N(p,γ ) 15 O reaction. The reaction proceeds by capture to the ground states and several excited states in 15 O. In order to obtain a reliable extrapolation of the excitation curve to astrophysical energy, fits in the R-matrix framework are needed. In an energy range that sensitively tests such fits, new cross-section data are reported here for the four major transitions in the 14 N(p,γ ) 15 O reaction. The experiment has been performed at the Laboratory for Underground Nuclear Astrophysics (LUNA) 400-kV accelerator placed deep underground in the Gran Sasso facility in Italy. Using a composite germanium detector, summing corrections have been considerably reduced with respect to previous studies. The cross sections for capture to the ground state and to the 5181, 6172, and 6792 keV excited states in 15 O have been determined at 359, 380, and 399 keV beam energy. In addition, the branching ratios for the decay of the 278-keV resonance have been remeasured.

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Section: Methodsmentioning

confidence: 99%

TheN14(p,γ)
Marta¹,
Formicola²,
Bemmerer³
et al. 2011
Phys. Rev. C
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“…5 We remind the readers that older versions of FRANEC instead used the abundances by Anders & Grevesse (1989), which are substantially different; (3) the use of new reaction rates of which crucial is in particular the new value for the 14 N(p, γ ) 15 O reaction (see the Appendix for details); in the FRANEC code this update was originally implemented when the measurements by the LUNA experiment became available (Imbriani et al 2005;Lemut et al 2006); (4) the adoption of new low-temperature opacities and their modifications during the evolution, when the envelope chemical admixture is changed by dredge-up and becomes carbon-rich (Cristallo et al 2007); (5) the choice, in evolved stages, of a mass-loss law different from the one previously used; this relation is similar to the one by Vassiliadis & Wood (1993), but adopts more recent data on the period-luminosity relation of AGB stars (see Straniero et al 2006 for details); and (6) a different treatment of the radiative/convective interfaces. In particular, instead of using a bare Schwarzschild criterion, an exponentially decreasing profile of the convective velocities was applied at the inner border of the convective envelope (Cristallo et al 2009a).…”

Section: The New Reference Stellar Modelsmentioning

confidence: 99%

DEEP MIXING IN EVOLVED STARS. I. THE EFFECT OF REACTION RATE REVISIONS FROM C TO Al

Palmerini

Cognata

Cristallo

et al. 2011

ApJ

131

159

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We present computations of nucleosynthesis in low-mass (LM) red giant branch (RGB) and asymptotic giant branch (AGB) stars of Population I experiencing extended mixing. We adopt the updated version of the FRANEC evolutionary model, a new post-process code for non-convective mixing and the most recent revisions for solar abundances. In this framework, we discuss the effects of recent improvements in relevant reaction rates for proton captures on intermediate-mass (IM) nuclei (from carbon to aluminum). For each nucleus, we briefly discuss the new choices and their motivations. The calculations are then performed on the basis of a parameterized circulation, where the effects of the new nuclear inputs are best compared to previous works. We find that the new rates (and notably the one for the 14 N(p, γ ) 15 O reaction) imply considerable modifications in the composition of post-mainsequence stars. In particular, the slight temperature changes due to the reduced efficiency of proton captures on 14 N induce abundance variations at the first dredge-up (especially for 17 O, whose equilibrium ratio to 16 O is very sensitive to the temperature). In this new scenario, presolar oxide grains of AGB origin turn out to be produced almost exclusively by very low mass stars (M 1.5-1.7 M ), never becoming C-rich. The whole population of grains with 18 O/ 16 O below 0.0015 (the limit permitted by first dredge-up) is now explained. Also, there is now no forbidden area for very low values of 17 O/ 16 O (below 0.0005), contrary to previous findings. A rather shallow type of transport seems to be sufficient for the CNO changes in RGB stages. Both thermohaline diffusion and magnetic-buoyancy-induced mixing might provide a suitable physical mechanism for this. Thermohaline mixing is in any case certainly inadequate to account for the production of 26 Al on the AGB. Other transport mechanisms must therefore be at play. In general, observational constraints from RGB and AGB stars, as well as from presolar grains, are well reproduced by our approach. The nitrogen isotopic ratio in mainstream SiC grains remains an exception. For the low values measured in them (i.e., for 14 N/ 15 N 2000), we have no explanation. Actually, for the several grains with subsolar nitrogen isotopic ratios, no known stellar process acting in LM stars can provide a clue. This might be an evidence that some form of contamination from cosmic ray spallation occurs in the interstellar medium, adding fresh 15 N to the grains.

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“…More recent measurements [11][12][13][14][15] have focused on the cross section around the lowest energy resonance at E p = 278 keV. The lowest energy measurement was carried out by the LUNA collaboration [13,14] down to E c.m. = 70 keV.…”

Section: Introductionmentioning

confidence: 99%

Cross section measurement ofN14(p,γ)O15in the CNO cycle

Görres

deBoer

et al. 2016

Phys. Rev. C

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Background The CNO cycle is the main energy source in stars more massive than our sun, it defines the energy production and the cycle time that lead to the lifetime of massive stars, and it is an important tool for the determination of the age of globular clusters. In our sun about 1.6% of the total solar neutrino flux comes from the CNO cycle. The largest uncertainty in the prediction of this CNO flux from the standard solar model comes from the uncertainty in the 14 N(p, γ) 15 O reaction rate, thus the determination of the cross section at astrophysical temperatures is of great interest.Purpose The total cross section of the 14 N(p, γ) 15 O reaction has large contributions from the transitions to the Ex = 6.79 MeV excited state and the ground state of 15 O. The Ex = 6.79 MeV transition is dominated by radiative direct capture, while the ground state is a complex mixture of direct and resonance capture components and the interferences between them. Recent studies have concentrated on cross section measurements at very low energies, but broad resonances at higher energy may also play a role. A single measurement has been made that covers a broad higher energy range but it has large uncertainties stemming from uncorrected summing effects. Further, the extrapolations of the cross section vary significantly depending on the data sets considered. Thus new direct measurements have been made to improve the previous high energy studies and to better constrain the extrapolation.Methods Measurements were performed at the low energy accelerator facilities of the nuclear science laboratory at the University of Notre Dame. The cross section was measured over the proton energy range from Ep = 0.7 to 3.6 MeV for both the ground state and the Ex = 6.79 MeV transitions at θ lab = 0• , 135• and 150• . Both TiN and implanted 14 N targets were utilized. γ-rays were detected using an array of high purity germanium detectors.Results The excitation function as well as angular distributions of the two transitions were measured. A multi-channel Rmatrix analysis was performed with the present data and is compared with previous measurements. The analysis covers a wide energy range so that the contributions from broad resonances and direct capture can be better constrained. ConclusionThe astrophysical S-factors of the Ex = 6.79 MeV and the ground state transitions were extrapolated to low energies with the newly measured differential cross section data. Based on the present work, the extrapolations yield

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First measurement of the 14N(p,γ)15O cross section down to 70 keV

Cited by 114 publications

References 27 publications

TheN14(p,γ)
Marta¹,
Formicola²,
Bemmerer³
et al. 2011
Phys. Rev. C
Self Cite

TheN14(p,γ)
Marta¹,
Formicola²,
Bemmerer³
et al. 2011
Phys. Rev. C
Self Cite

DEEP MIXING IN EVOLVED STARS. I. THE EFFECT OF REACTION RATE REVISIONS FROM C TO Al

Cross section measurement ofN14(p,γ)O15in the CNO cycle

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First measurement of the 14N(p,γ)15O cross section down to 70 keV

Cited by 114 publications

References 27 publications

TheN14(p,γ)Marta1, Formicola2, Bemmerer3 et al. 2011Phys. Rev. CSelf Cite

TheN14(p,γ)Marta1, Formicola2, Bemmerer3 et al. 2011Phys. Rev. CSelf Cite

DEEP MIXING IN EVOLVED STARS. I. THE EFFECT OF REACTION RATE REVISIONS FROM C TO Al

Cross section measurement ofN14(p,γ)O15in the CNO cycle

Contact Info

Product

Resources

About

TheN14(p,γ)
Marta¹,
Formicola²,
Bemmerer³
et al. 2011
Phys. Rev. C
Self Cite

TheN14(p,γ)
Marta¹,
Formicola²,
Bemmerer³
et al. 2011
Phys. Rev. C
Self Cite