The knowledge of the production of extinct radioactivities like 92Nb and 146Sm by photodisintegration processes in ccSN and SNIa models is essential for interpreting abundances in meteoritic material and for Galactic Chemical Evolution (GCE). The 92Mo/92Nb and 146Sm/144Sm ratios provide constraints for GCE and production sites. We present results for SNIa with emphasis on nuclear uncertainties.
The abundances of 92Nb and 146Sm in the early Solar System are determined from meteoritic analysis and their stellar production is attributed to the p process. We investigate if their origin from thermonuclear supernovae deriving from the explosion o
f white dwarfs with mass above the Chandrasekhar limit is in agreement with the abundance of 53Mn, another radionuclide present in the early Solar System and produced in the same events. A consistent solution for 92Nb and 53Mn cannot be found within the current uncertainties and requires that the 92Nb/92Mo ratio in the early Solar System is at least 50% lower than the current nominal value, which is outside its present error bars. A different solution is to invoke another production site for 92Nb, which we find in the alpha-rich freezeout during core-collapse supernovae from massive stars. Whichever scenario we consider, we find that a relatively long time interval of at least ~10 Myr must have elapsed from when the star-forming region where the Sun was born was isolated from the interstellar medium and the birth of the Sun. This is in agreement with results obtained from radionuclides heavier than iron produced by neutron captures and lends further support to the idea that the Sun was born in a massive star-forming region together with many thousands of stellar siblings.
We explore SNIa as p-process sources in the framework of two-dimensional SNIa models using enhanced s-seed distributions as directly obtained from a sequence of thermal pulse instabilities. The SNIa WD precursor is assumed to have reached the Chandra
sekhar mass limit in a binary system by mass accretion from a giant/main sequence companion. We apply the tracer-particle method to reconstruct the nucleosynthesis from the thermal histories of Lagrangian particles, passively advected in the hydrodynamic calculations. For each particle we follow the explosive nucleosynthesis with a detailed nuclear reaction network. We select tracers within the typical temperature range for p-process production, 1.5-3.7 109K, and analyse in detail their behaviour, exploring the influence of different s-process distributions on the p-process nucleosynthesis. We find that SNIa contribute to a large fraction of p-nuclei, both the light p-nuclei and the heavy-p nuclei at a quite flat average production factor. For the first time, the very abundant Ru and Mo p-isotopes are reproduced at the same level as the heavy p-nuclei. We investigate the metallicity effect on the p-process production. Starting with a range of s-seeds distributions obtained for different metallicities, running SNIa two-dimensional models and using a simple chemical evolution code, we give estimates of the SNIa contribution to the solar p-process composition. We find that SNIa contribute for at least 50% at the solar p-nuclei composition, in a primary way.
Type Ia supernovae are thought to be the outcome of the thermonuclear explosion of a carbon/oxygen white dwarf in a close binary system. Their optical light curve is powered by thermalized gamma-rays produced by the radioactive decay of 56Ni, the mos
t abundant isotope present in the debris. The maximum and the shape of the light curve strongly depends on the total amount and distribution of this freshly synthesized isotope, as well as on the velocity and density distribution of the ejecta. Gamma-rays escaping the ejecta have the advantage of their lower interaction with the ejecta, the possibility to distinguish among isotopes and the relative simplicity of their transport modelling, and can be used as a diagnostic tool for studying the structure of the exploding star and the characteristics of the explosion, as it has been proved in the case of SN2014J.
Rare information on photodisintegration reactions of nuclei with mass numbers $A approx 160$ at astrophysical conditions impedes our understanding of the origin of $p$-nuclei. Experimental determination of the key ($p,gamma$) cross sections has been
playing an important role to verify nuclear reaction models and to provide rates of relevant ($gamma,p$) reactions in $gamma$-process. In this paper we report the first cross section measurements of $^{160}$Dy($p,gamma$)$^{161}$Ho and $^{161}$Dy($p,n$)$^{161}$Ho in the beam energy range of 3.4 - 7.0 MeV, partially covering the Gamow window. Such determinations are possible by using two targets with various isotopic fractions. The cross section data can put a strong constraint on the nuclear level densities and gamma strength functions for $A approx$ 160 in the Hauser-Feshbach statistical model. Furthermore, we find the best parameters for TALYS that reproduce the A $thicksim$ 160 data available, $^{160}$Dy($p,gamma$)$^{161}$Ho and $^{162}$Er($p,gamma$)$^{163}$Tm, and recommend the constrained $^{161}$Ho($gamma,p$)$^{160}$Dy reaction rates over a wide temperature range for $gamma$-process network calculations. Although the determined $^{161}$Ho($gamma$, p) stellar reaction rates at the temperature of 1 to 2 GK can differ by up to one order of magnitude from the NON-SMOKER predictions, it has a minor effect on the yields of $^{160}$Dy and accordingly the $p$-nuclei, $^{156,158}$Dy. A sensitivity study confirms that the cross section of $^{160}$Dy($p$, $gamma$)$^{161}$Ho is measured precisely enough to predict yields of $p$-nuclei in the $gamma$-process.
Nuclear uncertainties in the production of $p$ nuclei in massive stars have been quantified in a Monte Carlo procedure. Bespoke temperature-dependent uncertainties were assigned to different types of reactions involving nuclei from Fe to Bi. Their si
multaneous impact was studied in postprocessing explosive trajectories for three different stellar models. It was found that the grid of mass zones in the model of a 25 $M_odot$ star, which is widely used for investigations of $p$ nucleosynthesis, is too crude to properly resolve the detailed temperature changes required for describing the production of $p$ nuclei. Using models with finer grids for 15 $M_odot$ and 25 $M_odot$ stars with initial solar metallicity, it was found that most of the production uncertainties introduced by nuclear reaction uncertainties are smaller than a factor of two. Since a large number of rates were varied at the same time in the Monte Carlo procedure, possible cancellation effects of several uncertainties could be taken into account. Key rates were identified for each $p$ nucleus, which provide the dominant contribution to the production uncertainty. These key rates were found by examining correlations between rate variations and resulting abundance changes. This method is superior to studying flow patterns, especially when the flows are complex, and to individual, sequential variation of a few rates.