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

Imbriani, G.; Costantini, H.; Formicola, A.; Vomiero, Alberto; Angulo, C.; Bemmerer, D.; Bonetti, R.; Broggini, C.; Confortola, F.; Corvisiero, P.; Cruz, J.; Descouvemont, Pierre; Fülöp, Zs.; Gervino, G.; Guglielmetti, A.; Gustavino, C.; Gyürky, Gy.; Jesus, A.P.; Junker, M.; Klug, J. N.; Lemut, A.; Menegazzo, R.; Prati, P.; Roca, V.; Rolfs, C.; Romano, M.; Rossi‐Alvarez, C.; Schümann, F.; Schürmann, D.; Somorjai, E.; Straniero, O.; Strieder, F.; Terrasi, F.; Trautvetter, H. P.

doi:10.1140/epja/i2005-10138-7

Cited by 228 publications

(285 citation statements)

References 22 publications

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“…Nuclear reaction rates are drawn from Caughlan & Fowler (1988) or the NACRE collaboration (Angulo et al 1999), with preference given to the latter when available. We used newer specific reaction rates for the reactions 14 N(p, γ) 15 O (Imbriani et al 2005) and 12 C(α, γ) 16 O (Kunz et al 2002). All other options took default values, which are described in the MESA instrument papers (Paxton et al 2011(Paxton et al , 2013 and available in the source code.…”

Section: Stellar Models and Fitting Proceduresmentioning

confidence: 99%

A new correction of stellar oscillation frequencies for near-surface effects

Ball

Gizon

2014

A&A

221

337

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Context. Space-based observations of solar-like oscillations present an opportunity to constrain stellar models using individual mode frequencies. However, current stellar models are inaccurate near the surface, which introduces a systematic difference that must be corrected. Aims. We introduce and evaluate two parametrizations of the surface corrections based on formulae given by Gough (1990, LNP, 367, 283). The first we call a cubic term proportional to ν 3 /I and the second has an additional inverse term proportional to ν −1 /I, where ν and I are the frequency and inertia of an oscillation mode. Methods. We first show that these formulae accurately correct model frequencies of two different solar models (Model S and a calibrated MESA model) when compared to observed BiSON frequencies. In particular, even the cubic form alone fits significantly better than a power law. We then incorporate the parametrizations into a modelling pipeline that simultaneously fits the surface effects and the underlying stellar model parameters. We apply this pipeline to synthetic observations of a Sun-like stellar model, solar observations degraded to typical asteroseismic uncertainties, and observations of the well-studied CoRoT target HD 52265. For comparison, we also run the pipeline with the scaled power-law correction proposed by Kjeldsen et al. (2008, ApJ, 683, L175). Results. The fits to synthetic and degraded solar data show that the method is unbiased and produces best-fit parameters that are consistent with the input models and known parameters of the Sun. Our results for HD 52265 are consistent with previous modelling efforts and the magnitude of the surface correction is similar to that of the Sun. The fit using a scaled power-law correction is significantly worse but yields consistent parameters, suggesting that HD 52265 is sufficiently Sun-like for the same power-law to be applicable. Conclusions. We find that the cubic term alone is suitable for asteroseismic applications and it is easy to implement in an existing pipeline. It reproduces the frequency dependence of the surface correction better than a power-law fit, both when comparing calibrated solar models to BiSON observations and when fitting stellar models using the individual frequencies. This parametrization is thus a useful new way to correct model frequencies so that observations of individual mode frequencies can be exploited.

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Section: Stellar Models and Fitting Proceduresmentioning

confidence: 99%

A new correction of stellar oscillation frequencies for near-surface effects

Ball

Gizon

2014

A&A

221

337

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“…Recently, the 14 N(p, γ) 15 O cross section has been measured by the LUNA collaboration close to 70 keV (see e.g. Imbriani et al 2005;Bemmerer et al 2006;Lemut et al 2006), leading to an improved estimate of the S (E) factor at astrophysical energies (S (0) = 1.61 ± 0.08 keV, about half of the value of the NACRE compilation by Angulo et al 1999).…”

Section: N(p γ) 15 O Cross Sectionmentioning

confidence: 99%

“…Brunish et al 1990), we adopted the updated rates by Hammer et al (2005) for the 12 C+α and by the LUNA collaboration (see Imbriani et al 2005, and references therein) for the 14 N + p cross sections. For the other nuclear reactions we adopted the same rates as in Ciacio et al (1997).…”

Section: Evolutionary Stellar Modelsmentioning

confidence: 99%

Uncertainties on the theoretical predictions for classical Cepheid pulsational quantities

Valle

Marconi²,

Degl’Innocenti

et al. 2009

A&A

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Context. With their period-luminosity relation, "classical Cepheids" (CC) are the most common primary distance indicators within the Local Group, also providing an absolute calibration of important secondary distance indicators. However, the predicted position of these pulsators in the HR diagram, along the so called blue loop, that is the expected distribution of Cepheids within the instability strip is affected by several model inputs, reflecting upon the predicted PL relation. Aims. The aim of this work is to quantitatively evaluate the effects on the theoretical PL relation of current uncertainties on the chemical abundances of Cepheids in the Large Magellanic Cloud (LMC) and on several physical assumptions adopted in the evolutionary models. We will separately analyse how the different factors influence the evolutionary and pulsational observables and the resulting PL relation. Methods. To achieve this goal we computed new sets of updated evolutionary and pulsational models. Results. As a result, we find that present uncertainties on the most relevant H and He burning reaction rates do not influence in a relevant way the loop extension in temperature. On the contrary, current uncertainties on the LMC chemical composition significantly affect the loop extension and also reflect in the morphology of the instability strip; however their influence on the predicted pulsational parameters is negligible. We also discussed how overshooting and mass loss, sometimes suggested as possible solutions for the long-standing problem of the Cepheid mass discrepancy, influence the ML relation and the pulsational parameters. Conclusions. In summary, the present uncertainties on the physical inputs adopted in the evolutionary codes and in the LMC chemical composition are negligible for the prediction of the main pulsational properties. On the other hand, the inclusion of overshooting in the previous hydrogen burning phase and/or of mass loss is expected to significantly change the resulting theoretical pulsational scenario for Cepheids, as well as the calibration of their distance scale. These systematic effects are expected to influence the theoretical Cepheid calibration of the secondary distance indicators and in turn the resulting evaluation of the Hubble constant.

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“…In the past ten years there have been several experiments that measured this cross section using both direct and indirect methods. In particular, the experiment performed by the LUNA collaboration (Imbriani et al 2005;Costantini et al 2009) has reached the lowest energy, about 70 keV, which corresponds to a stellar temperature of about 50 MK. It is worth noting that a reliable extrapolation of the LUNA data to the solar Gamow peak requires combining low-energy with high-energy data, namely the results of the LENA experiment at TUNL (Runkle et al 2005).…”

Section: Reaction Rate Uncertaintiesmentioning

confidence: 99%

Effects of nuclear cross sections on¹⁹F nucleosynthesis at low metallicities

Cristallo

Leva

Imbriani

et al. 2014

A&A

Self Cite

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Context. The origin of fluorine is a longstanding problem in nuclear astrophysics. It is widely recognized that asymptotic giant branch (AGB) stars are among the most important contributors to the Galactic fluorine production. Aims. In general, extant nucleosynthesis models overestimate the fluorine production by AGB stars with respect to observations. Although those differences are rather small at solar metallicity, low metallicity AGB stellar models predict fluorine surface abundances up to one order of magnitude larger than the observed ones. Methods. As part of a project devoted to reducing the uncertainties in the nuclear physics that affect the nucleosynthesis in AGB stellar models, we review the relevant nuclear reaction rates involved in the fluorine production or destruction. We perform this analysis on a model with initial mass M = 2 M and Z = 0.001. Results. We found that the major uncertainties are due to the 13 C(α,n) 16 O, the 19 F(α,p) 22 Ne, and the 14 N(p,γ) 15 O reactions. A change in the corresponding reaction rates within the present experimental uncertainties implies surface 19 F variations at the AGB tip lower than 10%, thus much smaller than observational uncertainties. For some α capture reactions, however, cross sections at astrophysically relevant energies are determined on the basis of nuclear models, in which some low-energy resonance parameters are very poorly known. Thus, larger variations in the rates of those processes cannot be excluded. That being so, we explore the effects of the variation in some α capture rates well beyond the current published uncertainties. The largest 19 F variations are obtained by varying the 15 N(α,γ) 19 F and the 19 F(α,p) 22 Ne reactions. Conclusions. The currently estimated uncertainties of the nuclear reaction rates involved in the production and destruction of fluorine produce minor 19 F variations in the ejecta of AGB stars. Analysis of some α capture processes that assume a wider uncertainty range determines 19 F abundances in better agreement with recent spectroscopic fluorine measurements at low metallicity. In the framework of this scenario, the 15 N(α,γ) 19 F and the 19 F(α,p) 22 Ne reactions show the strongest effects on fluorine nucleosynthesis. The presence of poorly known low-energy resonances make such a scenario possible, even if it is unlikely. We plan to measure these resonances directly.

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

Cited by 228 publications

References 22 publications

A new correction of stellar oscillation frequencies for near-surface effects

A new correction of stellar oscillation frequencies for near-surface effects

Uncertainties on the theoretical predictions for classical Cepheid pulsational quantities

Effects of nuclear cross sections on¹⁹F nucleosynthesis at low metallicities

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

Cited by 228 publications

References 22 publications

A new correction of stellar oscillation frequencies for near-surface effects

A new correction of stellar oscillation frequencies for near-surface effects

Uncertainties on the theoretical predictions for classical Cepheid pulsational quantities

Effects of nuclear cross sections on19F nucleosynthesis at low metallicities

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Effects of nuclear cross sections on¹⁹F nucleosynthesis at low metallicities