scholarly journals Experimental Nuclear Astrophysics With the Light Elements Li, Be and B: A Review

2021 ◽  
Vol 7 ◽  
Author(s):  
G.G. Rapisarda ◽  
L. Lamia ◽  
A. Caciolli ◽  
Chengbo Li ◽  
S. Degl’Innocenti ◽  
...  
Keyword(s):  
Reaction Rate ◽  
Main Sequence ◽  
Light Element ◽  
Reaction Rates ◽  
Big Bang ◽  
Trojan Horse ◽  
Electron Screening ◽  
Activation Technique ◽  
Light Elements ◽  
Trojan Horse Method

Light elements offer a unique opportunity for studying several astrophysical scenarios from Big Bang Nucleosynthesis to stellar physics. Understanding the stellar abundances of light elements is key to obtaining information on internal stellar structures and mixing phenomena in different evolutionary phases, such as the pre-main-sequence, main-sequence or red-giant branch. In such a case, light elements, i.e., lithium, beryllium and boron, are usually burnt at temperatures of the order of 2–5 × 106 K. Consequently, the astrophysical S(E)-factor and the reaction rate of the nuclear reactions responsible for the burning of such elements must be measured and evaluated at ultra-low energies (between 0 and 10 keV). The Trojan Horse Method (THM) is an experimental technique that allows us to perform this kind of measurements avoiding uncertainties due to the extrapolation and electron screening effects on direct data. A long Trojan Horse Method research program has been devoted to the measurement of light element burning cross sections at astrophysical energies. In addition, dedicated direct measurements have been performed using both in-beam spectroscopy and the activation technique. In this review we will report the details of these experimental measurements and the results in terms of S(E)-factor, reaction rate and electron screening potential. A comparison between astrophysical reaction rates evaluated here and the literature will also be given.

scholarly journals Theoretical Predictions of Surface Light Element Abundances in Protostellar and Pre-Main Sequence Phase

2021 ◽  
Vol 8 ◽  
Author(s):  
E. Tognelli ◽  
S. Degl’Innocenti ◽  
P. G. Prada Moroni ◽  
L. Lamia ◽  
R. G. Pizzone ◽  
...  
Keyword(s):  
Cross Sections ◽  
Main Sequence ◽  
Light Element ◽  
Element Abundance ◽  
Light Elements ◽  
Convective Envelope ◽  
Stellar Envelope ◽  
Element Abundances ◽  
Stellar Interior ◽  
Theoretical Predictions

Theoretical prediction of surface stellar abundances of light elements–lithium, beryllium, and boron–represents one of the most interesting open problems in astrophysics. As well known, several measurements of 7Li abundances in stellar atmospheres point out a disagreement between predictions and observations in different stellar evolutionary phases, rising doubts about the capability of present stellar models to precisely reproduce stellar envelope characteristics. The problem takes different aspects in the various evolutionary phases; the present analysis is restricted to protostellar and pre-Main Sequence phases. Light elements are burned at relatively low temperatures (T from ≈2 to ≈5 million degrees) and thus in the early evolutionary stages of a star they are gradually destroyed at different depths of stellar interior mainly by (p, α) burning reactions, in dependence on the stellar mass. Their surface abundances are strongly influenced by the nuclear cross sections, as well as by the extension toward the stellar interior of the convective envelope and by the temperature at its bottom, which depend on the characteristics of the star (mass and chemical composition) as well as on the energy transport in the convective stellar envelope. In recent years, a great effort has been made to improve the precision of light element burning cross sections. However, theoretical predictions surface light element abundance are challenging because they are also influenced by the uncertainties in the input physics adopted in the calculations as well as the efficiency of several standard and non-standard physical processes active in young stars (i.e. diffusion, radiative levitation, magnetic fields, rotation). Moreover, it is still not completely clear how much the previous protostellar evolution affects the pre-Main Sequence characteristics and thus the light element depletion. This paper presents the state-of-the-art of theoretical predictions for protostars and pre-Main Sequence stars and their light element surface abundances, discussing the role of (p, α) nuclear reaction rates and other input physics on the stellar evolution and on the temporal evolution of the predicted surface abundances.

scholarly journals The light elements in a helio- and asteroseismic perspective

2009 ◽  
Vol 5 (S268) ◽  
pp. 387-394
Author(s):  
Sylvie Vauclair
Keyword(s):  
Main Sequence ◽  
Light Element ◽  
Heavy Elements ◽  
Light Elements ◽  
Main Sequence Stars ◽  
General Introduction ◽  
Helium Content ◽  
Element Abundances ◽  
The Past

AbstractAsteroseismology is a powerful tool to derive stellar parameters, including the helium content and internal helium gradients, and the macroscopic motions which can lead to lithium, beryllium, and boron abundance variations. Precise determinations of these parameters need deep analyses for each individual stars. After a general introduction on helio and asteroseismology, I first discuss the solar case, the results which have been obtained in the past two decades, and the crisis induced by the new determination of the abundances of heavy elements. Then I discuss asteroseismology in relation with light element abundances, especially for the case of main sequence stars.

scholarly journals Trojan Horse Method: A tool to explore electron screening effect

2010 ◽  
Vol 202 ◽  
pp. 012018 ◽  
Author(s):  
R G Pizzone ◽  
C Spitaleri ◽  
S Cherubini ◽  
M La Cognata ◽  
L Lamia ◽  
...  
Keyword(s):  
Trojan Horse ◽  
Electron Screening ◽  
Screening Effect ◽  
Trojan Horse Method

scholarly journals Light Elements in the Universe

2021 ◽  
Vol 8 ◽  
Author(s):  
Sofia Randich ◽  
Laura Magrini
Keyword(s):  
Globular Clusters ◽  
Light Element ◽  
Big Bang ◽  
Stellar Structure ◽  
Age Dating ◽  
Sequence Evolution ◽  
Light Elements ◽  
Chemical Enrichment ◽  
Star Formation Histories ◽  
The Universe

Due to their production sites, as well as to how they are processed and destroyed in stars, the light elements are excellent tools to investigate a number of crucial issues in modern astrophysics: from stellar structure and non-standard processes at work in stellar interiors to age dating of stars; from pre-main sequence evolution to the star formation histories of young clusters and associations and to multiple populations in globular clusters; from Big Bang nucleosynthesis to the formation and chemical enrichment history of the Milky Way Galaxy and its populations, just to cite some relevant examples. In this paper, we focus on lithium, beryllium, and boron (LiBeB) and on carbon, nitrogen, and oxygen (CNO). LiBeB are rare elements, with negligible abundances with respect to hydrogen; on the contrary, CNO are among the most abundant elements in the Universe, after H and He. Pioneering observations of light-element surface abundances in stars started almost 70 years ago and huge progress has been achieved since then. Indeed, for different reasons, precise measurements of LiBeB and CNO are difficult, even in our Sun; however, the advent of state-of-the-art ground- and space-based instrumentation has allowed the determination of high-quality abundances in stars of different type, belonging to different Galactic populations, from metal-poor halo stars to young stars in the solar vicinity and from massive stars to cool dwarfs and giants. Noticeably, the recent large spectroscopic surveys performed with multifiber spectrographs have yielded detailed and homogeneous information on the abundances of Li and CNO for statistically significant samples of stars; this has allowed us to obtain new results and insights and, at the same time, raise new questions and challenges. A complete understanding of the light-element patterns and evolution in the Universe has not been still achieved. Perspectives for further progress will open up soon thanks to the new generation instrumentation that is under development and will come online in the coming years.

scholarly journals An increase in the 12C+12C fusion rate from resonances at astrophysical energies

2019 ◽  
Vol 52 (382) ◽  
pp. MISC6-MISC8
Author(s):  
Aurora Tumino
Keyword(s):  
Neutron Stars ◽  
Cross Sections ◽  
Coulomb Barrier ◽  
Reaction Rate ◽  
Nuclear Reactions ◽  
Massive Stars ◽  
Reaction Rates ◽  
Fusion Reactions ◽  
Trojan Horse Method ◽  
Carbon Burning

Carbon burning powers pivotal scenarios that influence the fate of stars, such as the late evolutionary stages of massive stars (exceeding eight solar masses), superbursts from accreting neutron stars and progenitors of Type Ia supernovae. It proceeds through the 12C+12C fusion reactions that produce an \( \alpha \) particle and neon-20 or a proton and sodium-23 —that is, 12C(12C, \( \alpha \) )20Ne and 12C(12C, \( p \))23Na— at temperatures greater than \( 0.4 \cdot 10^9 \) K, corresponding to astrophysical energies exceeding a megaelectronvolt (MeV), at which such nuclear reactions are more likely to occur in stars. The cross-sections for those carbon fusion reactions (probabilities that are required to calculate the rate of the reactions) have never been measured below 2 MeV because of exponential suppression arising from the Coulomb barrier (the Coulomb barrier is around 6 MeV). The reference rate at temperatures below \( 1.2\cdot 10^9 \) K relies on extrapolations that ignore the effects of possible low-lying resonances. In Tumino et al. (2018), we report the measurement of the 12C(12C, \( \alpha_{0,1} \)) 20Ne and 12C(12C, \( p_{0,1} \)) 23Na reaction rates (where the subscripts 0 and 1 stand for the ground and first excited states of 20Ne and 23Na, respectively) at centre-of-mass energies from 2.7 to 0.8 MeV using the Trojan Horse method and the deuteron in 14N. This is an indirect technique aiming at measuring low-energy nuclear reactions unhindered by the Coulomb barrier and free of electron screening. The deduced cross-sections exhibit several resonances that are responsible for a very large increase of the reaction rate at the relevant temperatures. In particular, around \( 5\cdot 10^8 \) K, the reaction rate is more than 25 times larger than the reference value. This finding may have significant implications such as lowering the temperatures and densities required for the ignition of carbon burning in massive stars and decreasing the superburst ignition depth in accreting neutron stars in the direction to reconcile observations with theoretical models.

scholarly journals Nuclear physics and its role for describing the early universe

2019 ◽  
Vol 49 ◽  
pp. 1960012 ◽  
Author(s):  
R. G. Pizzone ◽  
R. Spartá ◽  
M. La Cognata ◽  
L. Lamia ◽  
C. Spitaleri ◽  
...  
Keyword(s):  
Cross Sections ◽  
Nuclear Physics ◽  
Reaction Rates ◽  
Big Bang ◽  
Abundance Estimates ◽  
Bare Nucleus ◽  
Trojan Horse Method ◽  
Direct Cross ◽  
Primordial Abundance ◽  
Temperature Ranges

Big Bang Nucleosynthesis (BBN) requires several nuclear physics inputs and nuclear reaction rates. An up-to-date compilation of direct cross sections of [Formula: see text], [Formula: see text]He and [Formula: see text]He reactions is given, being these ones among the most uncertain bare-nucleus cross sections. An intense experimental effort has been carried on in the last decade to apply the Trojan Horse Method (THM) to study reactions of relevance for the BBN and measure their astrophysical S(E)-factor. The reaction rates and the relative error for the four reactions of interest are then numerically calculated in the temperature ranges of relevance for BBN [Formula: see text]. These value were then used as input physics for primordial nucleosynthesis calculations in order to evaluate their impact on the calculated primordial abundances and isotopical composition for H, He and Li. New results on the [Formula: see text]He reaction rate were also taken into account.These were compared with the observational primordial abundance estimates in different astrophysical sites. Reactions to be studied in perspective will also be discussed.

AN UPDATED6Li(p, α)3He REACTION RATE AT ASTROPHYSICAL ENERGIES WITH THE TROJAN HORSE METHOD

2013 ◽  
Vol 768 (1) ◽  
pp. 65 ◽  
Author(s):  
L. Lamia ◽  
C. Spitaleri ◽  
R. G. Pizzone ◽  
E. Tognelli ◽  
A. Tumino ◽  
...  
Keyword(s):  
Reaction Rate ◽  
Trojan Horse ◽  
Trojan Horse Method

scholarly journals Study of 3He(n,p)3H reaction at cosmological energies with trojan horse method

2020 ◽  
Vol 227 ◽  
pp. 02013 ◽  
Author(s):  
C. Spampinato ◽  
R.G. Pizzone ◽  
R. Spartà ◽  
M. Couder ◽  
W. Tan ◽  
...  
Keyword(s):  
Energy Range ◽  
Big Bang ◽  
Trojan Horse ◽  
Big Bang Nucleosynthesis ◽  
Preliminary Results ◽  
Trojan Horse Method ◽  
Gamow Energy ◽  
The Big Bang

In the network of reactions present in the Big Bang nucleosynthesis, the 3He(n, p)3H has an important role which impacts the final 7Li abundance. The Trojan Horse Method (THM) has been applied to the 3He(d, pt)H reaction in order to extract the astrophysical S(E)-factor of the 3He(n, p)3H in the Gamow energy range. The experiment will be described in the present work together with the first preliminary results.

scholarly journals New High-Precision Measurement of the Reaction Rate of the 18O(p, α)15N Reaction via THM

2009 ◽  
Vol 26 (3) ◽  
pp. 237-242 ◽  
Author(s):  
M. La Cognata ◽  
C. Spitaleri ◽  
A. M. Mukhamedzhanov ◽  
B. Irgaziev ◽  
R. E. Tribble ◽  
...  
Keyword(s):  
High Precision ◽  
Precision Measurement ◽  
Reaction Rate ◽  
Trojan Horse ◽  
High Precision Measurement ◽  
Spectroscopic Measurements ◽  
A Value ◽  
Trojan Horse Method ◽  
First Time ◽  
Measured Strength

AbstractThe 18O(p, α)15N reaction rate has been extracted by means of the Trojan-Horse method. For the first time the contribution of the 20-keV peak has been directly evaluated, giving a value about 35% larger than previously estimated. The present approach has allowed to improve the accuracy of a factor 8.5, as it is based on the measured strength instead of educated guesses or spectroscopic measurements. The contribution of the 90-keV resonance has been determined as well, which turned out to be of negligible importance to astrophysics.

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