We present new measurements of the 7 Be(p,γ) 8 B cross section fromĒcm = 116 to 2460 keV, that incorporate several improvements over our previously published experiment, also discussed here. Our new measurements lead to S17(0) = 22.1 ± 0.6(expt) ± 0.6(theor) eV b based on data from Ecm = 116 to 362 keV, where the central value is based on the theory of Descouvemont and Baye. The theoretical error estimate is based on the fit of 12 different theories to our low energy data. We compare our results to other S17(0) values extracted from both direct ( 7 Be(p,γ) 8 B) and indirect (Coulomb dissociation and heavy-ion reaction) measurements, and show that the results of these 3 types of experiments are not mutually compatible. We recommend a "best" value, S17(0) = 21.4 ± 0.5(expt) ± 0.6(theor) eV b, based on the mean of all modern direct measurements below the 1 + resonance. We also present S-factors at 20 keV which is near the center of the Gamow window: the result of our measurements is S17(20) = 21.4 ± 0.6(expt) ± 0.6(theor) eV b, and the recommended value is S17(20) = 20.7 ± 0.5(expt) ± 0.6(theor) eV b.PACS numbers: 26.20+f, 26.65+t, 25.40Lw

Context. Recent studies show that rotation significantly affects the s-process in massive stars. Aims. We provide tables of yields for non-rotating and rotating massive stars between 10 and 150 M at Z = 10 −3 ([Fe/H] = −1.8).Tables for different mass cuts are provided. The complete s-process is followed during the whole evolution with a network of 737 isotopes, from hydrogen to polonium. Methods. A grid of stellar models with initial masses of 10, 15, 20, 25, 40, 60, 85, 120, and 150 M and with an initial rotation rate of both 0% or 40% of the critical velocity was computed. Three extra models were computed in order to investigate the effect of faster rotation (70% of the critical velocity) and of a lower 17 O(α, γ) reaction rate. Results. At the considered metallicity, rotation has a strong impact on the production of s-elements for initial masses between 20 and 60 M . In this range, the first s-process peak is boosted by 2−3 dex if rotation is included. Above 60 M , s-element yields of rotating and non-rotating models are similar. Increasing the initial rotation from 40% to 70% of the critical velocity enhances the production of 40 Z 60 elements by ∼0.5−1 dex. Adopting a reasonably lower 17 O(α, γ) rate in the fast-rotating model (70% of the critical velocity) boosts again the yields of s-elements with 55 Z 82 by about 1 dex. In particular, a modest amount of Pb is produced. Together with s-elements, some light elements (particularly fluorine) are strongly overproduced in rotating models.

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The 18 F(p,α) 15 O reaction rate is crucial for constraining model predictions of the γ-ray observable radioisotope 18 F produced in novae. The determination of this rate is challenging due to particular features of the level scheme of the compound nucleus, 19 Ne, which result in interference effects potentially playing a significant role. The dominant uncertainty in this rate arises from interference between J π =3/2 + states near the proton threshold (Sp = 6.411 MeV) and a broad J π =3/2 + state at 665 keV above threshold. This unknown interference term results in up to a factor of 40 uncertainty in the astrophysical S-factor at nova temperatures. Here we report a new measurement of states in this energy region using the 19 F( 3 He,t) 19 Ne reaction. In stark contrast with previous assumptions we find at least 3 resonances between the proton threshold and Ecm=50 keV, all with different angular distributions. None of these are consistent with J π = 3/2 + angular distributions. We find that the main uncertainty now arises from the unknown proton-width of the 48 keV resonance, not from possible interference effects. Hydrodynamic nova model calculations performed indicate that this unknown width affects 18 F production by at least a factor of two in the model considered.PACS numbers: 26.50.+x, 26.30.Ca, 25.55.Kr Novae occur in binary systems where hydrogen-rich material is accreted from a companion star onto a white dwarf, leading to thermonuclear runaway and subsequent ejection of material. Their ejecta is thought to be the main source of 13 C, 15 N and 17 O in the Galaxy [1,2]. The relevant unstable nuclei are accessible to experiments, and consequently, novae are the only explosive environment where the nuclear physics input is almost entirely based on experimental data [3].However, there are a number of outstanding challenges in our understanding of nova explosions [4], one of which is to reproduce the amount of ejected material inferred from infrared and radio observations, which is systematically underestimated by models. An independent way to constrain the ejected masses would be the detection of γ-rays, produced at the explosion stage. When the envelope becomes optically thin, novae are expected to emit γ-rays, dominated by a prominent 511 keV line. Predicted detectability distances of this prompt γ-ray emission (about 2 -3 kpc [2]) strongly depend on the overall amount of 18 F (T 1/2 (β + )=110 mins) left over after the explosion. This is critically influenced by the 18 F(p,α) 15 O reaction. Sensitivity studies of the impact of reaction rates on nova nucleosynthesis suggest that rates should be known to a precision of, at least, 30% [3]. However, this rate is currently poorly understood and considerable experimental and theoretical effort has been focused on determining this rate ([5, 6] and references therein).Until recently, this rate was thought to be dominated by (i) the 3/2 − resonance at E cm = 330 keV, and (ii) the interference of the 3/2 + states, at 8 and 38 keV E cm , with the known, broad 3...