Search

Your search keyword '"Broggini, C"' showing total 31 results
Start Over Author "Broggini, C" Topic astrophysics
31 results on '"Broggini, C"'

1. Precision study of ground state capture in the 14N(p,gamma)15O reaction

Author

Marta, M., Formicola, A., Gyurky, Gy., Bemmerer, D., Broggini, C., Caciolli, A., Corvisiero, P., Costantini, H., Elekes, Z., Fulop, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Imbriani, G., Junker, M., Kunz, R., Lemut, A., Limata, B., Mazzocchi, C., Menegazzo, R., Prati, P., Roca, V., Rolfs, C., Romano, M., Alvarez, C. Rossi, Somorjai, E., Straniero, O., Strieder, F., Terrasi, F., Trautvetter, H. P., and Vomiero, A.

Subjects
Nuclear Experiment, Astrophysics
Abstract

The rate of the hydrogen-burning carbon-nitrogen-oxygen (CNO) cycle is controlled by the slowest process, 14N(p,gamma)15O, which proceeds by capture to the ground and several excited states in 15O. Previous extrapolations for the ground state contribution disagreed by a factor 2, corresponding to 15% uncertainty in the total astrophysical S-factor. At the Laboratory for Underground Nuclear Astrophysics (LUNA) 400 kV accelerator placed deep underground in the Gran Sasso facility in Italy, a new experiment on ground state capture has been carried out at 317.8, 334.4, and 353.3 keV center-of-mass energy. Systematic corrections have been reduced considerably with respect to previous studies by using a Clover detector and by adopting a relative analysis. The previous discrepancy has been resolved, and ground state capture no longer dominates the uncertainty of the total S-factor., Comment: Phys. Rev. C, rapid comm., accepted

Published
2008
Full Text
View/download PDF

2. Astrophysical S-factor of the 3He(alpha,gamma)7Be reaction measured at low energy via prompt and delayed gamma detection

Author

Confortola, F., Bemmerer, D., Costantini, H., Formicola, A., Gyürky, Gy., Bezzon, P., Bonetti, R., Broggini, C., Corvisiero, P., Elekes, Z., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Imbriani, G., Junker, M., Laubenstein, M., Lemut, A., Limata, B., Lozza, V., Marta, M., Menegazzo, R., Prati, P., Roca, V., Rolfs, C., Alvarez, C. Rossi, Somorjai, E., Straniero, O., Strieder, F., Terrasi, F., and Trautvetter, H. P.

Subjects
Nuclear Experiment, Astrophysics
Abstract

Solar neutrino fluxes depend both on astrophysical and on nuclear physics inputs, namely on the cross sections of the reactions responsible for neutrino production inside the Solar core. While the flux of solar 8B neutrinos has been recently measured at Superkamiokande with a 3.5% uncertainty and a precise measurement of 7Be neutrino flux is foreseen in the next future, the predicted fluxes are still affected by larger errors. The largest nuclear physics uncertainty to determine the fluxes of 8B and 7Be neutrinos comes from the 3He(alpha,gamma)7Be reaction. The uncertainty on its S-factor is due to an average discrepancy in results obtained using two different experimental approaches: the detection of the delayed gamma rays from 7Be decay and the measurement of the prompt gamma emission. Here we report on a new high precision experiment performed with both techniques at the same time. Thanks to the low background conditions of the Gran Sasso LUNA accelerator facility, the cross section has been measured at Ecm = 170, 106 and 93 keV, the latter being the lowest interaction energy ever reached. The S-factors from the two methods do not show any discrepancy within the experimental errors. An extrapolated S(0)= 0.560+/-0.017 keV barn is obtained. Moreover, branching ratios between the two prompt gamma-transitions have been measured with 5-8% accuracy., Comment: to be published in Physical Review C

Published
2007
Full Text
View/download PDF

3. 3He(alpha,gamma)7Be cross section at low energies

Author

Gyurky, Gy., Confortola, F., Costantini, H., Formicola, A., Bemmerer, D., Bonetti, R., Broggini, C., Corvisiero, P., Elekes, Z., Fulop, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Imbriani, G., Junker, M., Laubenstein, M., Lemut, A., Limata, B., Lozza, V., Marta, M., Menegazzo, R., Prati, P., Roca, V., Rolfs, C., Alvarez, C. Rossi, Somorjai, E., Straniero, O., Strieder, F., Terrasi, F., and Trautvetter, H. P.

Subjects
Nuclear Experiment, Astrophysics
Abstract

The flux of 7Be and 8B neutrinos from the Sun and the production of 7Li via primordial nucleosynthesis depend on the rate of the 3He(alpha,gamma)7Be reaction. In extension of a previous study showing cross section data at 127 - 167 keV center of mass energy, the present work reports on a measurement of the 3He(alpha,gamma)7Be cross section at 106 keV performed at Italy's Gran Sasso underground laboratory by the activation method. This energy is closer to the solar Gamow energy than ever reached before. The result is sigma = 0.567 +- 0.029(stat) +- 0.016(syst) nbarn. The data are compared with previous activation studies at high energy, and a recommended S(0) value for all 3He(alpha,gamma)7Be activation studies, including the present work, is given., Comment: Accepted for publication in PRC

Published
2007
Full Text
View/download PDF

4. Activation measurement of the 3He(alpha,gamma)7Be cross section at low energy

Author

Bemmerer, D., Confortola, F., Costantini, H., Formicola, A., Gyurky, Gy., Bonetti, R., Broggini, C., Corvisiero, P., Elekes, Z., Fulop, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Imbriani, G., Junker, M., Laubenstein, M., Lemut, A., Limata, B., Lozza, V., Marta, M., Menegazzo, R., Prati, P., Roca, V., Rolfs, C., Alvarez, C. Rossi, Somorjai, E., Straniero, O., Strieder, F., Terrasi, F., and Trautvetter, H. P.

Subjects
Nuclear Experiment, Astrophysics
Abstract

The nuclear physics input from the 3He(alpha,gamma)7Be cross section is a major uncertainty in the fluxes of 7Be and 8B neutrinos from the Sun predicted by solar models and in the 7Li abundance obtained in big-bang nucleosynthesis calculations. The present work reports on a new precision experiment using the activation technique at energies directly relevant to big-bang nucleosynthesis. Previously such low energies had been reached experimentally only by the prompt-gamma technique and with inferior precision. Using a windowless gas target, high beam intensity and low background gamma-counting facilities, the 3He(alpha,gamma)7Be cross section has been determined at 127, 148 and 169 keV center-of-mass energy with a total uncertainty of 4%. The sources of systematic uncertainty are discussed in detail. The present data can be used in big-bang nucleosynthesis calculations and to constrain the extrapolation of the 3He(alpha,gamma)7Be astrophysical S-factor to solar energies.

Published
2006
Full Text
View/download PDF

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

Author

Lemut, A., Bemmerer, D., Confortola, F., Bonetti, R., Broggini, C., Corvisiero, P., Costantini, H., Cruz, J., Formicola, A., Fulop, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyurky, Gy., Imbriani, G., Jesus, A. P., Junker, M., Limata, B., Menegazzo, R., Prati, P., Roca, V., Rogalla, D., Rolfs, C., Romano, M., Alvarez, C. Rossi, Schumann, F., Somorjai, E., Straniero, O., Strieder, F., Terrasi, F., and Trautvetter, H. P.

Subjects
Nuclear Experiment, Astrophysics
Abstract

In stars with temperatures above 20*10^6 K, hydrogen burning is dominated by the CNO cycle. Its rate is determined by the slowest process, the 14N(p,gamma)15O reaction. Deep underground in Italy's Gran Sasso laboratory, at the LUNA 400 kV accelerator, the cross section of this reaction has been measured at energies much lower than ever achieved before. Using a windowless gas target and a 4pi BGO summing detector, direct cross section data has been obtained down to 70 keV, reaching a value of 0.24 picobarn. The Gamow peak has been covered by experimental data for several scenarios of stable and explosive hydrogen burning. In addition, the strength of the 259 keV resonance has been remeasured. The thermonuclear reaction rate has been calculated for temperatures 90 - 300 *10^6 K, for the first time with negligible impact from extrapolations.

Published
2006
Full Text
View/download PDF

6. The bottleneck of the CNO burning and the age of the Globular Clusters

Author

Imbriani, G., Costantini, H., Formicola, A., Bemmerer, D., Bonetti, R., Broggini, C., Corvisiero, P., Cruz, J., Fulop, Z., Gervino, G., Guglielmetti, A., Gustavino, C., Gyurky, G., Jesus, A. P., Junker, M., Lemut, A., Menegazzo, R., Prati, P., Roca, V., Rolfs, C., Romano, M., Alvarez, C. Rossi, Schumann, F., Somorjai, E., Straniero, O., Strieder, F., Terrasi, F., Trautvetter, H. P., Vomiero, A., and Zavatarelli, S.

Subjects
Astrophysics
Abstract

The transition between the Main Sequence and the Red Giant Branch in low mass stars is powered by the onset of the CNO burning, whose bottleneck is the $^{14}$N(p,$\gamma)^{15}$O. The LUNA collaboration has recently improved the low energy measurements of the cross section of this key reaction. We analyse the impact of the revised reaction rate on the estimate of the Globular Clusters ages, as derived from the turnoff luminosity. We found that the age of the oldest Globulars should be increased by about 0.7-1 Gyr with respect to the current estimates., Comment: Accepted

Published
2004
Full Text
View/download PDF

7. The Cross Section of 3He(3He,2p)4He measured at Solar Energies

Author

The LUNA Collaboration, Junker, M., D'Alessandro, A., Zavatarelli, S., Arpesella, C., Bellotti, E., Broggini, C., Corvisiero, P., Fiorentini, G., Fubini, A., Gervino, G., Greife, U., Gustavino, C., Lambert, J., Prati, P., Rodney, W. S., Rolfs, C., Strieder, F., Trautvetter, H. P., and Zahnow, D.

Subjects
Nuclear Experiment, Astrophysics
Abstract

We report on the results of the \hethet\ experiment at the underground accelerator facility LUNA (Gran Sasso). For the first time the lowest projectile energies utilized for the cross section measurement correspond to energies below the center of the solar Gamow peak ($E_{\rm 0}$=22 keV). The data provide no evidence for the existence of a hypothetical resonance in the energy range investigated. Although no extrapolation is needed anymore (except for energies at the low-energy tail of the Gamow peak), the data must be corrected for the effects of electron screening, clearly observed the first time for the \hethet\ reaction. The effects are however larger than expected and not understood, leading presently to the largest uncertainty on the quoted $S_{\rm b}(E_{\rm 0})$ value for bare nuclides (=5.40 MeV b)., Comment: 18 pages, 10 postscript figures, Calculations concerning hypothetical resonanz added, Submitted to Phys. Rev. C., available at this URL: HTTP://www.lngs.infn.it/lngs/htexts/luna/luna.html

Published
1997
Full Text
View/download PDF

8. 22Ne and23Na ejecta from intermediate-mass stars: The impact of the new LUNA rate for 22Ne(p, γ)23Na

Author

Slemer, A., Marigo, P., Piatti, D., Aliotta, M., Bemmerer, D., Best, A., Boeltzig, A., Bressan, A., Broggini, C., Bruno, C. G., Caciolli, A., Cavanna, F., Ciani, G. F., Corvisiero, P., Davinson, T., Depalo, R., Di Leva, A., Elekes, Z., Ferraro, F., Formicola, A., F\\\', Zs., l\\\', p, Gervino, G., Guglielmetti, A., Gustavino, C., Gy\\\', G., rky, Imbriani, G., Junker, M., Menegazzo, R., Mossa, V., Pantaleo, F. R., Prati, P., Straniero, O., Sz\\\', T., Tak\', M. P., Trezzi, D., Slemer, A., Marigo, P., Piatti, D., Aliotta, M., Bemmerer, D., Best, Andrea, Boeltzig, A., Bressan, A., Broggini, C., Bruno, C. G., Caciolli, A., Cavanna, F., Ciani, G. F., Corvisiero, P., Davinson, T., Depalo, R., DI LEVA, Antonino, Elekes, Z., Ferraro, F., Formicola, A., Fülöp, Z. s., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, G., Imbriani, Gianluca, Junker, M., Menegazzo, R., Mossa, V., Pantaleo, F. R., Prati, P., Straniero, O., Szücs, T., Takács, M. P., and Trezzi, D.

Subjects
Stars: mass loss, abundances – stars: abundances – stars: AGB and post-AGB – stars: carbon – stars: evolution – stars: mass loss, K-type main-sequence star, Metallicity, Astrophysics, nuclear reactions, nucleosynthesis, abundances, stars: abundances, stars: AGB and post-AGB, stars: carbon, stars: evolution, stars: mass loss, 01 natural sciences, Settore FIS/05 - Astronomia e Astrofisica, 0103 physical sciences, Asymptotic giant branch, Abundances, 010306 general physics, Ejecta, 010303 astronomy & astrophysics, Physics, Stars: abundances, Stars: AGB and post-AGB, Order (ring theory), Astronomy, Astronomy and Astrophysics, Stars, T Tauri star, Stars: carbon, Stars: evolution, nuclear reactions, nucleosynthesis, abundances – stars: abundances – stars: AGB and post-AGB – stars: carbon – stars: evolution – stars: mass loss, Astrophysics - Solar and Stellar Astrophysics, Nuclear reactions, Nucleosynthesis, Space and Planetary Science, 13. Climate action, Stellar mass loss
Abstract

We investigate the impact of the new LUNA rate for the nuclear reaction $^{22}$Ne$(p,\gamma)^{23}$Na on the chemical ejecta of intermediate-mass stars, with particular focus on the thermally-pulsing asymptotic giant branch (TP-AGB) stars that experience hot-bottom burning. To this aim we use the PARSEC and COLIBRI codes to compute the complete evolution, from the pre-main sequence up to the termination of the TP-AGB phase, of a set of stellar models with initial masses in the range $3.0\,M_{\odot} - 6.0\,M_{\odot}$, and metallicities $Z_{\rm i}=0.0005$, $Z_{\rm i}=0.006$, and $Z_{\rm i} = 0.014$. We find that the new LUNA measures have much reduced the nuclear uncertainties of the $^{22}$Ne and $^{23}$Na AGB ejecta, which drop from factors of $\simeq 10$ to only a factor of few for the lowest metallicity models. Relying on the most recent estimations for the destruction rate of $^{23}$Na, the uncertainties that still affect the $^{22}$Ne and $^{23}$Na AGB ejecta are mainly dominated by evolutionary aspects (efficiency of mass-loss, third dredge-up, convection). Finally, we discuss how the LUNA results impact on the hypothesis that invokes massive AGB stars as the main agents of the observed O-Na anti-correlation in Galactic globular clusters. We derive quantitative indications on the efficiencies of key physical processes (mass loss, third dredge-up, sodium destruction) in order to simultaneously reproduce both the Na-rich, O-poor extreme of the anti-correlation, and the observational constraints on the CNO abundance. Results for the corresponding chemical ejecta are made publicly available., Comment: 21 pages, 14 figures, accepted for publication in MNRAS

Published
2017

9. Three New Low-Energy Resonances in the Ne-22(p,gamma)Na-23 Reaction

Author

Cavanna, F., Depalo, R., Aliotta, M., Anders, M., Bemmerer, D., Best, A., Boeltzig, A., Broggini, C., Bruno, C., Caciolli, A., Corvisiero, P., Davinson, T., Di Leva, A., Elekes, Z., Ferraro, F., Formicola, A., Fülöp, Z., Gervino, Gianpiero, Guglielmetti, A., Gustavino, C., Gyürky, G., Imbriani, G., Junker, M., Menegazzo, R., Mossa, V., Pantaleo, F., Prati, P., Scott, D. A., Somorjai, E., Straniero, O., Strieder, F., Szücs, T., Takács, M. P., and Trezzi, D.

Subjects
Astrophysics, Chemical elements, Giant stars, Reaction rates, Sodium, Stars Asymptotic giant branch stars, Direct observations, Energy resonance, High purity germanium detectors, Nuclear astro-physics, Proton energy, Resonance strengths, Sodium cycle
Published
2015

10. Underground measurement of 14N(p, γ)15O astrophysical factor at low energy

Author

Confortola, F., Bemmerer, D., Costantini, H., Formicola, A., Gyurky, G. y., Bezzon, P., Bonetti, R., Broggini, C., Corvisiero, P., Elekes, Z., Fulop, Z., Gervino, Gianpiero, Guglielmetti, A., Gustavino, C., Imbriani, G., Junker, M., Laubenstein, M., Lemut, A., Limata, B., Lozza, V., Marta, M., Menegazzo, R., Prati, P., Roca, V., Rolfs, C., Rossi Alvarez, C., Somorjai, E., Straniero, O., Strieder, F., Terrasi, F., and Trautvetter, H. P.

Subjects
Physics, History, CNO cycle, Proton, Solar neutrino, nuclear astrophysics, Cosmic ray, Astrophysics, Computer Science Applications, Education, Nuclear physics, Nuclear astrophysics, Nuclear fusion, Neutrino, Nuclear Experiment, Borexino
Abstract

In stars, four hydrogen nuclei are converted into a helium nucleus by two competing nuclear fusion processes: the proton - proton chain (p-p) and the carbon - nitrogen - oxygen (CNO) cycle. At temperatures higher than 2 107 K, the CNO cycle dominates the energy production. In particular, its rate is determined by the slowest reaction: 14N(p, γ)15O. Direct measurement in a laboratory at the surface of the Earth is hampered by the background due to the cosmic rays. Here we report on an experiment performed with the LUNA (Laboratory for Underground Nuclear Astrophysics) accelerator placed deep underground in the Gran Sasso laboratory (Italy). Thanks to the cosmic ray suppression provided by the mountain shield, we could measure the 14N(p, γ)15O cross section for the first time directly at energies corresponding to stellar temperatures and with unprecedented accuracy. The results are strictly related to carbon stars formation, an independent lower limit on the age of the universe and solar neutrinos flux. The 13N and 15O neutrinos coming from the CNO cycle are strictly correlated to the 14N(p, γ)15O S-factor and their flux will play an important role in some future solar neutrino experiment, such as Borexino.

Published
2006
Full Text
View/download PDF

11. Lifetime measurement of the 6.79 MeV state in 15O with the AGATA demonstrator.

Author

Depalo, R., Michelagnoli, C., Menegazzo, R., Ur, C. A., Bazzacco, D., Bemmerer, D., Broggini, C., Caciolli, A., Erhard, M., Farnea, E., Fülöp, Zs., Gottardo, A., Keeley, N., Lunardi, S., Marta, M., Mengoni, D., Mijatovic, T., Recchia, F., Rossi-Alvarez, C., and Szücs, T.

Subjects
ASTROPHYSICS, GAMMA rays, NEUTRINOS, KINEMATICS, GERMANIUM diodes
Abstract

The 14N(p,γ)15O reaction is the slowest process of the CN cycle, and thus it is of high astrophysical interest since it regulates the total rate of energy and neutrinos production through the cycle. The 14N+p ground state capture is strongly influenced by a sub-threshold resonance corresponding to the 6.79 MeV state in 15O. The width of this resonance is a major source of uncertainty in the extrapolation of the reaction cross section in the Gamow energy window. Preliminary results of a new Doppler Shift Attenuation measurement of the lifetime of the 6.79 MeV state in 15O are discussed. The level of interest was populated via the 2H(14N,n)15O reaction in inverse kinematics at 32 MeV beam energy. The gamma-rays emitted in the decay of the 6.79 MeV level to the ground state were detected with the AGATA Demonstrator array of high-purity germanium detectors. The sensitivity of the shape of the peak in the gamma-ray energy spectrum to the level lifetime is investigated comparing the experimental peaks with detailed Monte Carlo simulations of the reaction mechanisms and the gamma-ray emission and detection. Nuclear levels in 15N (also populated in the 14N+2H reaction) for which the lifetimes are known in the literature provided a test of the analysis technique. [ABSTRACT FROM AUTHOR]

Published
2012
Full Text
View/download PDF

12. Nuclear Astrophysics At LUNA: Status And Perspectives.

Author

Prati, P., Bemmerer, D., Bonetti, R., Broggini, C., Corvisiero, P., Confortola, F., Conti, E., Costantini, H., Elekes, Z., Formicola, A., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gyürky, Gy., Gustavino, C., Imbriani, G., Junker, M., Lemut, A., Limata, B., and Marta, M.

Subjects
NUCLEAR physics, ASTROPHYSICS, NEUTRINOS, NEUTRONS, NUCLEAR reactions
Abstract

The talk will be mainly devoted to the measurement of the cross section of the 3He(α,γ)7Be reaction which belongs to the p-p chain. Actually, solar neutrino fluxes depend both on astrophysical and on nuclear physics inputs, namely on the cross sections of the reactions responsible for neutrino production inside the Solar core. While the flux of solar 8B neutrinos has been recently measured at Superkamiokande with a 3.5% uncertainty and a precise measurement of 7Be neutrino flux is foreseen in the next future, the predicted fluxes are still affected by larger errors. The largest nuclear physics uncertainty to determine the fluxes of 8B and 7Be neutrinos comes from the 3He(α,γ)7Be reaction. The uncertainty on its S-factor is due to an average discrepancy in results obtained using two different experimental approaches: the detection of the delayed γ rays from 7Be decay and the measurement of the prompt γ emission. The LUNA Collaboration has performed a new high precision experiment with both techniques at the same time. Thanks to the low background conditions of the Gran Sasso LUNA accelerator facility, the cross section has been measured down to 93 keV, the lowest interaction energy ever reached. The S-factors from the two methods do not show any discrepancy within the experimental errors. An extrapolated S(0) = 0.560±0.017 keV barn is obtained. Moreover, branching ratios between the two prompt γ -transitions have been measured with 3–8% accuracy. Recently, the LUNA Collaboration has presented to the Scientific Board of Gran Sasso Laboratory its experimental program for the next five years based on the existing 400 kV accelerator facility. A Letter of Intent addressing the possibility to install a 3 MV machine at Gran Sasso has also been submitted to the Board. The LUNA scientific programs with both the 400 kV and 3 MV accelerator facilities will be illustrated in the final part of the talk. [ABSTRACT FROM AUTHOR]

Published
2008
Full Text
View/download PDF

13. Electron Screening: A Review.

Author

Raiola, F., Cruz, J., Gyürky, G., Fülöp, Z., Zeng, S., Aliotta, M., Becker, H. W., Burchard, B., Broggini, C., Di Leva, A., D'Onofrio, A., Fonseca, M., Gang, L., Gialanella, L., Imbriani, G., Jesus, A. P., Junker, M., Kettner, K. U., Limata, B., and Luis, H.

Subjects
ELECTRONS, PARTICLES (Nuclear physics), ASTROPHYSICS, STARS, NUCLEAR physics, PHYSICS
Abstract

Understanding the electron screening effect in the laboratory is critical for a correct interpretation of low-energy nuclear reactions in stars. Extensive studies of the electron screening effect in deuterated metals (54 metals) and other environments have been carried out in Bochum in the last 4 years. Experimental results of anomalous enhancements have been interpreted in terms of the Debye plasma model applied to quasi-free metallic electrons. For the d(d,p)t reaction in metallic environments, the variation of hydrogen solubility in the samples as a function of temperature has also been measured, showing an anti-correlation with screening enhancement as expected. Within this model, the deduced number of valence electrons per metallic atom also agrees with the corresponding number from the Hall coefficient. Recently, the expected temperature dependence of the screening potential has been verified together with the expected Zt scaling (with the metallic host) of the Debye radius. Preliminary results on the 7Li(p,α) and 6Li(p,α) reactions in Li2WO4 insulator, Li metal and PdLi alloys confirm the expected behaviour of the screening effect and further supports the applicability of the Debye model. Indeed, the proposed model also accounts for the high screening potential (Ue = 900±50 eV) observed in previous studies of the reactions 9Be(p,α) and 9Be(p,d), which was not understood at the time. A review of all these results will be presented. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2006
Full Text
View/download PDF

14. CNO hydrogen burning studied deep underground.

Author

Fülöp, Zsolt, Gyürky, György, Somorjai, Endre, Bemmerer, D., Confortola, F., Lemut, A., Bonetti, R., Broggini, C., Corvisiero, P., Costantini, H., Cruz, J., Formicola, A., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, Gy., Imbriani, G., Jesus, A. P., and Junker, M.

Abstract

In stars, four hydrogen nuclei are converted into a helium nucleus in two competing nuclear fusion processes, namely the proton-proton chain (p-p chain)and the carbon-nitrogen-oxygen (CNO) cycle. For temperatures above 20 million kelvin, the CNO cycle dominates energy production, and its rate is determined by the slowest process, the 14N(p, γ)15O radiative capture reaction. This reaction proceeds through direct and resonant capture into the ground state and several excited states in 15O. High energy data for capture into each of these states can be extrapolated to stellar energies using an R-matrix fit. The results from several recent extrapolation studies are discussed. A new experiment at the LUNA (Laboratory for Underground Nuclear Astrophysics) 400 kV accelerator in Italy's Gran Sasso laboratory measures the total cross section of the 14N(p, γ)15O reaction with a windowless gas target and a 4π BGO summing detector, down to center of mass energies as low as 70 keV. After reviewing the characteristics of the LUNA facility, the main features of this experiment are discussed, as well as astrophysical scenarios where cross section data in the energy range covered have a direct impact, without any extrapolation. [ABSTRACT FROM AUTHOR]

Published
2006
Full Text
View/download PDF

15. Towards a high-precision measurement of the 3He(α, γ)7Be cross section at LUNA.

Author

Fülöp, Zsolt, Gyürky, György, Somorjai, Endre, Costantini, H., Bemmerer, D., Bezzon, P., Bonetti, R., Broggini, C., Casanova, M. L., Confortola, F., Corvisiero, P., Cruz, J., Elekes, Z., Formicola, A., Fülop, Zs., Gervino, G., Gustavino, C., Guglielmetti, A., Gyürky, Gy., and Imbriani, G.

Abstract

The 3He(4He, γ)7Be reaction is the key process for the production of 7Be and 8B neutrinos in the Sun. We have designed a new experimental setup to study this reaction with high accuracy at low energies using two different experimental techniques. The first method consists in measuring the prompt capture gamma-ray transitions with an ultra-low background germanium detector heavily shielded and placed at close distance from a 3He windowless gas target. With another fully shielded large-volume germanium detector we will also measure the β-decay of the 7Be residual nuclei. The aim of the experiment is to reduce the error on the astrophysical factor S3,4 to 4%. [ABSTRACT FROM AUTHOR]

Published
2006
Full Text
View/download PDF

16. Enhanced d(d,p)t fusion reaction in metals.

Author

Fülöp, Zsolt, Gyürky, György, Somorjai, Endre, Raiola, F., Burchard, B., Fülöp, Zs., Gyürky, Gy., Zeng, S., Cruz, J., Di Leva, A., Limata, B., Fonseca, M., Luis, H., Aliotta, M., Becker, H. W., Broggini, C., D'Onofrio, A., Gialanella, L., Imbriani, G., and Jesus, A. P.

Abstract

The electron screening in the d(d,p)t reaction has been studied for the deuterated metal Pt at a target temperature T = 20 °C to 340 °C, and for Co at T = 20 °C and 200 °C. The enhanced electron screening decreases with increasing temperature, where the data agree with the plasma model of Debye applied to the quasi-free metallic electrons. The data represent the first observation of a temperature dependence of a nuclear cross-section. We also measured the screening effect for the deuterated metal Ti (an element of group 4 of the periodic table) at T = −10 °C to 200 °C: above 50 °C the hydrogen solubility dropped to values far below unity and a large screening effect became observable. Similarly, all metals of groups 3 and 4 and the lanthanides showed a solubility of a few percent at T = 200 °C ( compared to T = 20 °C) and a large screening became also observable. Within the Debye model the deduced number of valence electrons per metallic atom agrees with the corresponding number from the Hall coefficient, for all metals investigated. [ABSTRACT FROM AUTHOR]

Published
2006
Full Text
View/download PDF

17. LUNA results and implications for solar neutrinos and cosmology

Author

Broggini, C.

Subjects
*SOLAR neutrinos, *METAPHYSICAL cosmology, *ASTROPHYSICS, *NUCLEAR physics
Abstract

Abstract: LUNA, Laboratory for Underground Nuclear Astrophysics at Gran Sasso, is studying thermonuclear reactions down to the energy of the nucleosynthesis inside stars. Significant results, relevant for neutrino physics and cosmology, have been the measurements of 3He(3He, 2p)4He within the Gamow peak of the Sun and of 14N(p, )15O down to very low energy. The results will be presented and their implications will be discussed. [Copyright &y& Elsevier]

Published
2006
Full Text
View/download PDF

18. Enhanced d(d,p)t fusion reaction in metals.

Author

Raiola, F., Burchard, B., Fülöp, Zs., Gyürky, Gy., Zeng, S., Cruz, J., Di Leva, A., Limata, B., Fonseca, M., Luis, H., Aliotta, M., Becker, H. W., Broggini, C., D'Onofrio, A., Gialanella, L., Imbriani, G., Jesus, A. P., Junker, M., Ribeiro, J. P., and Roca, V.

Subjects
CONTROLLED fusion, METALS, NUCLEAR reactions, ASTROPHYSICS, NUCLEAR cross sections, ELECTRONS
Abstract

The electron screening in the d(d,p)t reaction has been studied for the deuterated metal Pt at a target temperature $\ensuremath T = 20 ^{\circ}$ C to $\ensuremath 340 ^{\circ}$ C, and for Co at $\ensuremath T = 20 ^{\circ}$ C and $\ensuremath 200 ^{\circ}$ C. The enhanced electron screening decreases with increasing temperature, where the data agree with the plasma model of Debye applied to the quasi-free metallic electrons. The data represent the first observation of a temperature dependence of a nuclear cross-section. We also measured the screening effect for the deuterated metal Ti (an element of group 4 of the periodic table) at $\ensuremath T = -10 ^{\circ}$ C to $\ensuremath 200 ^{\circ}$ C: above $\ensuremath 50 ^{\circ}$ C the hydrogen solubility dropped to values far below unity and a large screening effect became observable. Similarly, all metals of groups 3 and 4 and the lanthanides showed a solubility of a few percent at $\ensuremath T = 200 ^{\circ}$ C (compared to $\ensuremath T = 20 ^{\circ}$ C) and a large screening became also observable. Within the Debye model the deduced number of valence electrons per metallic atom agrees with the corresponding number from the Hall coefficient, for all metals investigated. [ABSTRACT FROM AUTHOR]

Published
2006
Full Text
View/download PDF

19. S-factor of 14N(p,γ)15O at astrophysical energies⋆.

Author

Imbriani, G., Costantini, H., Formicola, A., Vomiero, A., Angulo, C., Bemmerer, D., Bonetti, R., Broggini, C., Confortola, F., Corvisiero, P., Cruz, J., Descouvemont, P., Fülöp, Z., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, Gy., Jesus, A., Junker, M., and Klug, J. N.

Subjects
ASTROPHYSICS, SPECIAL relativity (Physics), RELATIVITY (Physics), RELATIVISTIC quantum theory, NUCLEOSYNTHESIS, CHEMICAL elements, SOLAR neutrinos, GAMMA ray spectrometry
Abstract

The astrophysical S( E) factor of 14N(p,γ)15O has been measured for effective center-of-mass energies between Eeff = 119 and 367 keV at the LUNA facility using TiN solid targets and Ge detectors. The data are in good agreement with previous and recent work at overlapping energies. R-matrix analysis reveals that due to the complex level structure of 15O the extrapolated S(0) value is model dependent and calls for additional experimental efforts to reduce the present uncertainty in S(0) to a level of a few percent as required by astrophysical calculations. [ABSTRACT FROM AUTHOR]

Published
2005
Full Text
View/download PDF

20. Feasibility of low-energy radiative-capture experiments at the LUNA underground accelerator facility.

Author

Bemmerer, D., Confortola, F., Lemut, A., Bonetti, R., Broggini, C., Corvisiero, P., Costantini, H., Cruz, J., Formicola, A., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, Gy., Imbriani, G., Jesus, A. P., Junker, M., Limata, B., Menegazzo, R., and Prati, P.

Subjects
LABORATORIES, RADIATION, ASTROPHYSICS, ELECTROSTATICS, ELECTRON accelerators, GAMMA rays
Abstract

The LUNA (Laboratory Underground for Nuclear Astrophysics) facility has been designed to study nuclear reactions of astrophysical interest. It is located deep underground in the Gran Sasso National Laboratory, Italy. Two electrostatic accelerators, with 50 and 400 kV maximum voltage, in combination with solid and gas target setups allowed to measure the total cross-sections of the radiative-capture reactions ^2H2H(p, ?)^3He3Heand ^14N14N(p, ?)^15O15Owithin their relevant Gamow peaks. We report on the gamma background in the Gran Sasso laboratory measured by germanium and bismuth germanate detectors, with and without an incident proton beam. A method to localize the sources of beam-induced background using the Doppler shift of emitted gamma rays is presented. The feasibility of radiative-capture studies at energies of astrophysical interest is discussed for several experimental scenarios. [ABSTRACT FROM AUTHOR]

Published
2005
Full Text
View/download PDF

21. LUNA results

Author

Broggini, C.

Subjects
*NUCLEAR astrophysics, *ASTROPHYSICS, *STARS, *NUCLEOSYNTHESIS
Abstract

LUNA, Laboratory for Underground Nuclear Astrophysics, is studying thermonuclear reactions down to the energy of the stellar nucleosynthesis. The latest experiments performed by LUNA, i.e. the measurement of the 14N(p,γ)15O and 3He(α,γ)7Be cross sections, will be presented and their implications will be discussed. [Copyright &y& Elsevier]

Published
2007
Full Text
View/download PDF

22. Underground study of the 17O(p,alpha)18F reaction relevant for explosive hydrogen burning

Author

Di Leva, A, Scott, D.A., Caciolli, A., Formicola, A., Strieder, F., Aliotta, M., Anders, M., Bemmerer, D., Broggini, C., Corvisiero, P., Elekes, Z., Fulop, Zs., Gervino, G., Guglielmetti, G., Gustavino, C., Gyurky, Gy., Imbriani, G., José Pont, Jordi|||0000-0002-9937-2685, Junker, M., Universitat Politècnica de Catalunya. Departament de Física i Enginyeria Nuclear, and Universitat Politècnica de Catalunya. GAA - Grup d'Astronomia i Astrofísica

Subjects
Astrofísica, Astrophysics::High Energy Astrophysical Phenomena, Física::Astronomia i astrofísica [Àrees temàtiques de la UPC], Astrophysics
Abstract

The 17O(p,γ )18F reaction affects the production of key isotopes (e.g., 18F and 18O) in the explosive hydrogen burning that powers classical novae. Under these explosive conditions, the reaction rate is dominated by contributions from a narrow resonance at Ec.m.= 183 keV and by the combined contributions of direct capture and low-energy tails of broad resonances. At present, the astrophysical reaction rate is not well constrained because of the lack of data in the energy region appropriate to classical novae.

23. Direct measurements of low-energy resonance strengths of the 23Na(p,γ)24Mg reaction for astrophysics.

Author

Boeltzig, A., Best, A., Pantaleo, F.R., Imbriani, G., Junker, M., Aliotta, M., Balibrea-Correa, J., Bemmerer, D., Broggini, C., Bruno, C.G., Buompane, R., Caciolli, A., Cavanna, F., Chillery, T., Ciani, G.F., Corvisiero, P., Csedreki, L., Davinson, T., deBoer, R.J., and Depalo, R.

Subjects
*NUCLEAR astrophysics, *ASYMPTOTIC giant branch stars, *ASTROPHYSICS, *RESONANCE, *COSMIC rays, *GERMANIUM radiation detectors
Abstract

The NeNa and the MgAl cycles play a fundamental role in the nucleosynthesis of asymptotic giant branch stars undergoing hot bottom burning. The Na 23 (p , γ) 24 Mg reaction links these two cycles and a precise determination of its rate is required to correctly estimate the contribution of these stars to the chemical evolution of various isotopes of Na, Mg and Al. At temperatures of 50 ≲ T ≲ 110 MK , narrow resonances at E p = 140 and 251 keV are the main contributors to the reaction rate, in addition to the direct capture that dominates in the lower part of the temperature range. We present new measurements of the strengths of these resonances at the Laboratory for Underground Nuclear Astrophysics (LUNA). We have used two complementary detection approaches: high efficiency with a 4 π BGO detector for the 140 keV resonance, and high resolution with a HPGe detector for the 251 keV resonance. Thanks to the reduced cosmic ray background of LUNA, we were able to determine the resonance strength of the 251 keV resonance as ω γ = 482 (82) μ eV and observed new gamma ray transitions for the decay of the corresponding state in Mg 24 at E x = 11931 keV. With the highly efficient BGO detector, we observed a signal for the 140 keV resonance for the first time in a direct measurement, resulting in a strength of ω γ 140 = 1.46 − 0.53 + 0.58 neV (68% CL). Our measurement reduces the uncertainty of the Na 23 (p , γ) 24 Mg reaction rate in the temperature range from 0.05 to 0.1 GK to at most − 35 % + 50 % at 0.07 GK. Accordingly, our results imply a significant reduction of the uncertainties in the nucleosynthesis calculations. [ABSTRACT FROM AUTHOR]

Published
2019
Full Text
View/download PDF

24. Improved astrophysical rate for the 18O(p,α)15N reaction by underground measurements

Author

Roberto Menegazzo, Pierre Descouvemont, Z. Elekes, M. P. Takács, Thomas Davinson, C. G. Bruno, P. Corvisiero, Oscar Straniero, Gianluca Imbriani, A. Guglielmetti, Marialuisa Aliotta, Antonio Caciolli, V. Mossa, D. Piatti, A. Boeltzig, Tamás Szücs, Davide Trezzi, A. Di Leva, Paolo Prati, G. F. Ciani, Zs. Fülöp, Maria Lugaro, Paola Marigo, F. Cavanna, K. Stöckel, A. Best, C. Gustavino, D. Bemmerer, Frank Strieder, T. Chillery, C. Broggini, M. Junker, F. R. Pantaleo, R. Depalo, A. Formicola, Gy. Gyürky, G. Gervino, F. Ferraro, Bruno, C. G., Aliotta, M., Descouvemont, P., Best, A., Davinson, T., Bemmerer, D., Boeltzig, A., Broggini, C., Caciolli, A., Cavanna, F., Chillery, T., Ciani, G. F., Corvisiero, P., Depalo, R., Di Leva, A., Elekes, Z., Ferraro, F., Formicola, A., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, Gy., Imbriani, G., Junker, M., Lugaro, M., Marigo, P., Menegazzo, R., Mossa, V., Pantaleo, F. R., Piatti, D., Prati, P., Stöckel, K., Straniero, O., Strieder, F., Szücs, T., Takács, M. P., and Trezzi, D.

Subjects
Nuclear and High Energy Physics, Astrophysics, 01 natural sciences, 7. Clean energy, Hydrostatic stellar nucleosynthesis, Nucleosynthesis, Stellar hydrogen burningHydrostatic stellar nucleosynthesis, 0103 physical sciences, Nuclear astrophysics, Asymptotic giant branch, 010306 general physics, Stellar hydrogen burning, Hydrostatic stellar nucleosynthesi, Physics, Isotope, 010308 nuclear & particles physics, Resonance, Atmospheric temperature range, Physique atomique et nucléaire, lcsh:QC1-999, Stars, 13. Climate action, Center of mass, Stellar hydrogen burning, Hydrostatic stellar nucleosynthesis, lcsh:Physics
Abstract

The 18O(p,α)15N reaction affects the synthesis of 15N, 18O and 19F isotopes, whose abundances can be used to probe the nucleosynthesis and mixing processes occurring deep inside asymptotic giant branch (AGB) stars. We performed a low-background direct measurement of the 18O(p,α)15N reaction cross-section at the Laboratory for Underground Nuclear Astrophysics (LUNA) from center of mass energy Ec.m.=340 keV down to Ec.m.=55 keV, the lowest energy measured to date corresponding to a cross-section of less than 1 picobarn/sr. The strength of a key resonance at center of mass energy Er=90 keV was found to be a factor of 10 higher than previously reported. A multi-channel R-matrix analysis of our and other data available in the literature was performed. Over a wide temperature range, T=0.01–1.00 GK, our new astrophysical rate is both more accurate and precise than recent evaluations. Stronger constraints can now be placed on the physical processes controlling nucleosynthesis in AGB stars with interesting consequences on the abundance of 18O in these stars and in stardust grains, specifically on the production sites of oxygen-rich Group II grains., SCOPUS: ar.j, info:eu-repo/semantics/published

Published
2019
Full Text
View/download PDF

25. The 25Mg(p, γ)26Al reaction at low astrophysical energies

Author

Strieder, F., Limata, B., Formicola, A., Imbriani, G., Junker, M., Bemmerer, D., Best, A., Broggini, C., Caciolli, A., Corvisiero, P., Costantini, H., DiLeva, A., Elekes, Z., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, Gy., Lemut, A., and Marta, M.

Subjects
*RESONANCE, *MAGNESIUM, *BISMUTH compounds, *ASTROPHYSICS, *GERMANIUM diodes
Abstract

Abstract: In the present work we report on a new measurement of resonance strengths ωγ in the reaction 25Mg(p, γ)26Al at and 189 keV. This study was performed at the LUNA facility in the Gran Sasso underground laboratory using a 4π BGO summing crystal. For the first time the 92 keV resonance was directly observed and a resonance strength was determined. Additionally, the γ-ray branchings and strength of the 189 keV resonance were studied with a high resolution HPGe detector yielding an ωγ value in agreement with the BGO measurement, but 20% larger compared to previous works. [Copyright &y& Elsevier]

Published
2012
Full Text
View/download PDF

26. Ultra-sensitive γ-ray spectroscopy set-up for investigating primordial lithium problem.

Author

Gervino, G., Gustavino, C., Trezzi, D., Aliotta, M., Anders, M., Boeltzig, A., Bemmerer, D., Best, A., Broggini, C., Bruno, C., Caciolli, A., Cavanna, F., Corvisiero, P., Davinson, T., Depalo, R., DiLeva, A., Elekes, Z., Ferraro, F., Formicola, A., and Fülöp, Zs.

Subjects
*LITHIUM, *GERMANIUM radiation detectors, *SPECTROMETRY, *NUCLEAR reactions, *ASTROPHYSICS
Abstract

To precisely determine BBN 6 Li production, the cross-section of the nuclear reaction 2 H(α, γ) 6 Li must be directly measured within the astrophysical energy range of 30–400 keV. This measure requires an ultra-low γ-ray background in the experimental set-up. We have realized the conditions matching these very strict requirements at LUNA, the deep underground accelerator laboratory active in the INFN Gran Sasso National Laboratory (LNGS), Italy: the γ-ray spectrometer background has been reduced down to reach unmatched low levels, comparable to the good ones experienced in dedicated off-line underground ultra low γ counting rate. We present and discuss the γ-ray background reduction reached in the HpGe spectrometer, where most of the remaining γ-ray background seen in the spectra are coming from the energetic deuterons scattered in the gas target by the α beam. Thanks to the low neutron environmental background at LUNA, the effect of this weak flux of 2–3 MeV neutrons on HpGe detectors has been studied in details and the results are presented and discussed. [ABSTRACT FROM AUTHOR]

Published
2016
Full Text
View/download PDF

27. S-factor of 14N(p,γ)15O at astrophysical energies⋆.

Author

Imbriani, G., Costantini, H., Formicola, A., Vomiero, A., Angulo, C., Bemmerer, D., Bonetti, R., Broggini, C., Confortola, F., Corvisiero, P., Cruz, J., Descouvemont, P., Fülöp, Z., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, Gy., Jesus, A., Junker, M., and Klug, J. N.

Subjects
*ASTROPHYSICS, *SPECIAL relativity (Physics), *RELATIVITY (Physics), *RELATIVISTIC quantum theory, *NUCLEOSYNTHESIS, *CHEMICAL elements, *SOLAR neutrinos, *GAMMA ray spectrometry
Abstract

The astrophysical S( E) factor of 14N(p,γ)15O has been measured for effective center-of-mass energies between Eeff = 119 and 367 keV at the LUNA facility using TiN solid targets and Ge detectors. The data are in good agreement with previous and recent work at overlapping energies. R-matrix analysis reveals that due to the complex level structure of 15O the extrapolated S(0) value is model dependent and calls for additional experimental efforts to reduce the present uncertainty in S(0) to a level of a few percent as required by astrophysical calculations. [ABSTRACT FROM AUTHOR]

Published
2005
Full Text
View/download PDF

28. Astrophysical <f>S</f>-factor of 14N<f>(p,γ)</f>15O

Author

Formicola, A., Imbriani, G., Costantini, H., Angulo, C., Bemmerer, D., Bonetti, R., Broggini, C., Corvisiero, P., Cruz, J., Descouvemont, P., Fülöp, Z., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, G., Jesus, A.P., Junker, M., Lemut, A., Menegazzo, R., and Prati, P.

Subjects
*ASTROPHYSICS, *NUMERICAL analysis, *HUMAN error, *APPROXIMATION theory
Abstract

We report on a new measurement of the 14N(p,γ)15O capture cross section at Ep=140 to 400 keV using the 400 kV LUNA accelerator facility at the Laboratori Nazionali del Gran Sasso (LNGS). The uncertainties have been reduced with respect to previous measurements and their analysis. We have analyzed the data using the R-matrix method and we find that the ground state transition accounts for about 15% of the total S-factor. The main contribution to the S-factor is given by the transition to the 6.79 MeV state. We find a total S(0)=1.7±0.2 keV b, in agreement with recent extrapolations. The result has important consequences for the solar neutrino spectrum as well as for the age of globular clusters. [Copyright &y& Elsevier]

Published
2004
Full Text
View/download PDF

29. Cross-section measurements at astrophysically relevant energies: The LUNA experiment.

Author

Formicola, A., Bruno, C.G., Caciolli, A., Cavanna, F., Depalo, R., Di Leva, A., Scott, D.A., Trezzi, D., Aliotta, M., Anders, M., Bemmerer, D., Broggini, C., Corvisiero, P., Elekes, Z., Fülöp, Zs., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, Gy., and Imbriani, G.

Subjects
*ASTROPHYSICS, *NUCLEAR reactions, *LUMINOSITY, *NEUTRINOS, *COSMIC background radiation, *NUCLEOSYNTHESIS
Abstract

Abstract: Accurate knowledge of thermonuclear reaction rates is important in understanding the generation of energy, the luminosity of neutrinos, and the synthesis of elements in stars. Cross-section measurements for quiescent stellar H-burning are mainly hampered by extremely low counting rate and cosmic background. The LUNA Collaboration has shown that, by going underground and by using the typical techniques of low background physics, it is possible to measure nuclear cross-sections down to the energy of the nucleosynthesis inside stars. This paper reports an overview of the experimental techniques adopted in underground nuclear astrophysics through a summary of the main recent results and achievements. The future developments of the LUNA experiment are also given. [Copyright &y& Elsevier]

Published
2014
Full Text
View/download PDF

30. The impact of the revised17O(p, α)14N reaction rate on17O stellar abundances and yields

Author

M. Junker, F. Ferraro, M. P. Takács, Gianluca Imbriani, Zsolt Fülöp, R. Menegazzo, Thomas Davinson, E. Samorjai, Sergio Cristallo, Paolo Prati, A. Di Leva, C. G. Bruno, Z. Elekes, D. K. Trezzi, Gyuri Gyürky, Oscar Straniero, F. R. Pantaleo, Marialuisa Aliotta, G. Gervino, F. Cavanna, Antonio Caciolli, Daniel Bemmerer, C. Gustavino, P. Corvisiero, V. Mossa, G. F. Ciani, Rosanna Depalo, A. Best, A. Formicola, A. Boeltzig, Luciano Piersanti, Carlo Broggini, A. Guglielmetti, D. Piatti, Tamás Szücs, Frank Strieder, Straniero, O., Bruno, C. G., Aliotta, M., Best, Andrea, Boeltzig, A., Bemmerer, D., Broggini, C., Caciolli, A., Cavanna, F., Ciani, G. F., Corvisiero, P., Cristallo, S., Davinson, T., Depalo, R., DI LEVA, Antonino, Elekes, Z., Ferraro, F., Formicola, A., Fülöp, Z. s., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, G., Imbriani, Gianluca, Junker, M., Menegazzo, R., Mossa, V., Pantaleo, F. R., Piatti, D., Piersanti, L., Prati, P., Samorjai, E., Strieder, F., Szücs, T., Takács, M. P., and Trezzi, D.

Subjects
CNO cycle, Nuclear reactions, nucleosynthesis, abundances – Stars: abundances – Stars: evolution, Nuclear reactions, nucleosynthesis, abundances, Stars: abundances, Stars: evolution, Astronomy and Astrophysics, Space and Planetary Science, Astrophysics, Dredge-up, 01 natural sciences, abundances – Stars: abundances – Stars: evolution, Nucleosynthesis, 0103 physical sciences, Nuclear Astrophysics, Nuclear astrophysics, 010306 general physics, 010303 astronomy & astrophysics, Physics, abundances, nucleosynthesis, Giant star, Interstellar medium, Red-giant branch, Stars, Astrophysics - Solar and Stellar Astrophysics, Nuclear reactions
Abstract

Context. Material processed by the CNO cycle in stellar interiors is enriched in 17O. When mixing processes from the stellar surface reach these layers, as occurs when stars become red giants and undergo the first dredge up, the abundance of 17O increases. Such an occurrence explains the drop of the 16O/17O observed in RGB stars with mass larger than 1.5 M_\solar. As a consequence, the interstellar medium is continuously polluted by the wind of evolved stars enriched in 17O . Aims. Recently, the Laboratory for Underground Nuclear Astrophysics (LUNA) collaboration released an improved rate of the 17O(p,alpha)14N reaction. In this paper we discuss the impact that the revised rate has on the 16O/17O ratio at the stellar surface and on 17O stellar yields. Methods. We computed stellar models of initial mass between 1 and 20 M_\solar and compared the results obtained by adopting the revised rate of the 17O(p,alpha)14N to those obtained using previous rates. Results. The post-first dredge up 16O/17O ratios are about 20% larger than previously obtained. Negligible variations are found in the case of the second and the third dredge up. In spite of the larger 17O(p,alpha)14N rate, we confirm previous claims that an extra-mixing process on the red giant branch, commonly invoked to explain the low carbon isotopic ratio observed in bright low-mass giant stars, marginally affects the 16O/17O ratio. Possible effects on AGB extra-mixing episodes are also discussed. As a whole, a substantial reduction of 17O stellar yields is found. In particular, the net yield of stars with mass ranging between 2 and 20 M_\solar is 15 to 40% smaller than previously estimated. Conclusions. The revision of the 17O(p,alpha)14N rate has a major impact on the interpretation of the 16O/17O observed in evolved giants, in stardust grains and on the 17O stellar yields., Comment: Accepted by A&A

Published
2017

31. Revision of the 15N(p, γ)16O reaction rate and oxygen abundance in H-burning zones

Author

Gianluca Imbriani, G. Gervino, A. Formicola, Zs. Fülöp, C. Rolfs, V. Capogrosso, Oscar Straniero, Filippo Terrasi, Alberto Vomiero, Antonio Caciolli, E. Somorjai, Gy. Gyürky, H. P. Trautvetter, Z. Elekes, A. Guglielmetti, Carlo Broggini, Frank Strieder, C. Gustavino, H. Costantini, Sara Palmerini, P. Corvisiero, C. Mazzocchi, M. Marta, Vincenzo Roca, Paolo Prati, M. Junker, A. Lemut, R. Menegazzo, C. Rossi Alvarez, Daniel Bemmerer, Caciolli, A., Mazzocchi, C., Capogrosso, V., Bemmere, D., Broggini, C., Corvisiero, P., Costantini, H., Elekes, Z., Formicola, A., Fülöp, Z., Gervino, G., Guglielmetti, A., Gustavino, C., Gyürky, G., Imbriani, Gianluca, Junker, M., Lemut, A., Marta, M., Menegazzo, R., Palmerini, S., Prati, P., Roca, Vincenzo, Rolfs, C., Rossi Alvarez, C, Somorjai, E., Straniero, O., Strieder, F., Terrasi, F., Trautvetter, H. P., and Vomiero, A.

Subjects
Cataclysmic variables, Novae, Nuclear reaction, abundances, Stars: AGB and post-AGB, Population, nuclear astrophysics, CNO Cycle, Astrophysics, 01 natural sciences, Reaction rate, Nucleosynthesis, 0103 physical sciences, Asymptotic giant branch, education, Novae, Nuclear Experiment, 010303 astronomy & astrophysics, Cataclysmic variables, Physics, education.field_of_study, abundances, 010308 nuclear & particles physics, Nuclear reactions, nucleosynthesis, abundances, Stars: AGB and post-AGB, Astronomy and Astrophysics, Space and Planetary Science, nucleosynthesis, Giant star, Red-giant branch, Stars, Astrophysics - Solar and Stellar Astrophysics, nucleosynthesi, 13. Climate action, Globular cluster, Nuclear reactions
Abstract

The NO cycle takes place in the deepest layer of a H-burning core or shell, when the temperature exceeds T {\simeq} 30 {\cdot} 106 K. The O depletion observed in some globular cluster giant stars, always associated with a Na enhancement, may be due to either a deep mixing during the RGB (red giant branch) phase of the star or to the pollution of the primordial gas by an early population of massive AGB (asymptotic giant branch) stars, whose chemical composition was modified by the hot bottom burning. In both cases, the NO cycle is responsible for the O depletion. The activation of this cycle depends on the rate of the 15N(p,{\gamma})16O reaction. A precise evaluation of this reaction rate at temperatures as low as experienced in H-burning zones in stellar interiors is mandatory to understand the observed O abundances. We present a new measurement of the 15N(p,{\gamma})16O reaction performed at LUNA covering for the first time the center of mass energy range 70-370 keV, which corresponds to stellar temperatures between 65 {\cdot} 106 K and 780 {\cdot}106 K. This range includes the 15N(p,{\gamma})16O Gamow-peak energy of explosive H-burning taking place in the external layer of a nova and the one of the hot bottom burning (HBB) nucleosynthesis occurring in massive AGB stars. With the present data, we are also able to confirm the result of the previous R-matrix extrapolation. In particular, in the temperature range of astrophysical interest, the new rate is about a factor of 2 smaller than reported in the widely adopted compilation of reaction rates (NACRE or CF88) and the uncertainty is now reduced down to the 10% level., Comment: 6 pages, 5 figures

Published
2011

Catalog

Books, media, physical & digital resources
See catalog results