F. STRIEDER

In stars with temperatures above 20 × 106 K, hydrogen burning is dominated by the CNO cycle. Its rate is determined by the slowest process, the 14N(p, γ )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...

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...

We report on measurements of resonance strengths and energies for the Ep = 151 and 193 keV resonances in the 18O(p,gamma)15N and 17O(p,gamma)14N reactions, respectively, obtained during commissioning of a new setup for alpha-particle detection studies at the LUNA underground laboratory. Our values, omegagamma(151) = 164.2 ± 0.9 stat+12.1−11.7...

Classical novae are important contributors to the abundances of key isotopes, such as the radioactive 18F, whose observation by satellite missions could provide constraints on nucleosynthesis models in novae. The 17O(p,gamma)18F reaction plays a critical role in the synthesis of both oxygen and fluorine isotopes but its reaction rate is not...

Classical novae are important contributors to the abundances of key isotopes, such as the radioactive 18F, whose observation by satellite missions could provide constraints on nucleosynthesis models in novae. The 17Oðp; Þ18F reaction plays a critical role in the synthesis of both oxygen and fluorine isotopes, but its reaction rate is not well...

The 22Ne(p,gamma)23Na reaction takes part in the neon-sodium cycle of hydrogen burning. This cycle is active in asymptotic giant branch stars as well as in novae and contributes to the nucleosythesis of neon and sodium isotopes. In order to reduce the uncertainties in the predicted nucleosynthesis yields, new experimental efforts to measure the...

The direct measurement of reaction cross sections at astrophysical energies often requires the use of solid targets of known thickness, isotopic composition, and stoichiometry that are able to withstand high beam currents for extended periods of time. Here, we report on the production and characterisation of isotopically enriched Ta2O5 targets...

Direct measurements of small nuclear reaction cross sections require a low background in the signal region of interest to achieve the necessary sensitivity. We describe two complementary detector setups that have been used for studies of (p, gamma) reactions with solid targets at the Laboratory for Underground Nuclear Astrophysics (LUNA): a...

The observation of oxygen isotopes in giant stars sheds light on mixing processes operating in their interiors. Due to the very strong correlation between nuclear burning and mixing processes it is very important to reduce the uncertainty on the cross sections of the nuclear reactions that are involved. In this paper we focus our attention on...

The NeNa and the MgAl cycles play a fundamental role in the nucleosynthesis of asymptotic giant branch stars undergoing hot bottom burning. The 23Na(p, γ)24Mgreaction 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...