The production of the p-process nuclei in stars is still an open problem for nuclear astrophysics. Current supernova models seem to not produce enough of them, and their high abundances in the Solar System represent a challenge for stellar nucleosynthesis. Different scenarios have been proposed to solve these issues, but more work is needed. In this context, the p-process nuclei provide an...
The lack of knowledge of $\alpha$-nuclear potentials in unstable nuclei constitutes one of the main uncertainties associated to the modeling of the production of heavy p-nuclei [1,2]. Global parametrizations used to model the elastic scattering cross section of α particles on radioactive nuclei may differ up to a factor of 2, with a corresponding impact in the determination of...
The p-nuclei, rich in protons, are created through a specific nucleosynthesis process involving numerous reactions such as (γ, n), (γ, p), and (γ, α) in explosive astrophysical events like supernovae. The research aims to adjust astrophysical scenarios to replicate the observed abundances of these nuclei. A significant challenge in this research is the uncertainty in alpha-nucleus optical...
The existence of some stable neutron deficient nuclei - the p nuclei - can not be explained by neutron-capture processes [1]. Therefore, other types of reactions - dominantly photodisintegration reactions - come into play. This is called the $\gamma$ process. Statistical model calculations play a crucial role in modelling this process as cross sections for many of these photodisintegration...
Heterogeneities in the nucleosynthetic composition of meteorites for the p-nuclides are less common than for s-process isotopes and have been identified for 84Sr (e.g. Charlier et al., 2021), 144Sm (e.g. Andreasen and Sharma, 2006), 174Hf (Peters et al., 2017) and 180W (Cook et al., 2018). The origin of p-nuclide heterogeneity is unclear and is not related to specific presolar grains found in...
Since the very first p-process workshop in Vravron, Greece (2002), theoretical
study of the astrophysical p-process is accompanied by nuclear physics experiments.
These experiments always try to follow the requirements from astrophysical models
and reaction cross sections relevant to the p-process have been measured on various
type of reactions with various techniques. These experiments do...
Understanding the origin of the p nuclides has been an ongoing challenge within the astrophysics community for over 60 years. In the extensively researched $\gamma$ process the reaction flow involves photodisintegration reactions on a vast network of mostly radioactive isotopes. However, as experimental cross sections of $\gamma$-process reactions are very limited, and almost entirely...
O-C shell mergers in massive stars have been proposed as a potential site for the production of p-process isotopes. These mergers provide a convective-reactive environment where the timescales for the nucleosynthesis of C-shell ashes such as $^{20}\mathrm{Ne}$ and convective mixing of species are of the same order. However, the nucleosynthetic pathways of these convective-reactive processes...
The p-process nucleosynthesis can explain proton-rich isotopes that are heavier than iron, which are observed in the Solar System, but discrepancies still persist (e.g. for the Mo and Ru p-isotopes).
We investigate both the systematic and statistical uncertainties associated with theoretical nuclear reaction rates of relevance during the p-process and explore their impact on the p-process...
By definition, the proton-rich isotopes that cannot be reached by neutron-capture processes are the p-only isotopes or the p-nuclei. However, several p-nuclei can produced by the s process in low-mass AGB stars, e.g. (1) $\mathrm{^{94}Mo}$ by two consecutive neutron captures of $\mathrm{^{92}Mo}$ and following the decay of $\mathrm{^{93}Zr}$ and $\mathrm{^{94}Nb}$, (2)...
The $\gamma$-process in core-collapse supernovae (CCSNe) can produce a number of neutron-deficient stable isotopes heavier than iron (p-nuclei). However, current model predictions do to not fully reproduce the solar abundances. We investigate the impact of different explosion energies and parameters on the nucleosynthesis of p-nuclei, by studying stellar models with different initial masses...
The production of the light p-nuclei 113In and 115Sn has been a long-standing problem for $\gamma$-process nucleosynthesis [1,2]. The reaction flow in the Cd-In-Sn region is rather complicated due to the existance of several long-lived $\beta$-decaying isomers, which leads to a general underproduction of these isotopes compared to the other p-nuclei. In this talk, I will discuss the current...
Presolar grains are relic dust grains from dying stars. These microscopic dust particles are found in primitive Solar System materials. Their distinct isotopic compositions record the nucleosynthetic processes in their parent stars and the galactic chemical environment in which these stars formed. We studied presolar graphite grains of high-density type from the Murchison meteorite and found...
In this talk, I will introduce STIR, a model that incorporates neutrino-driven convection in 1D simulations of core-collapse supernovae (Couch et al. 2020, Boccioli et al. 2021). This model has the advantage of being more sophisticated than other 1D models adopted for similar studies and is able to reproduce recent results from 2D and 3D state-of-the-art simulations of core-collapse...
The astrophysical origins of the heaviest stable elements that we observe today in the Solar System are still not fully understood. Recent studies have demonstrated that H-accreting white dwarfs (WDs) in a binary system exploding as type Ia supernovae could be an efficient p-process source beyond iron. However, both observational evidence and stellar models challenge the required frequency of...
This presentation brings into focus $^{78,80}$Kr($\gamma$,$\gamma’$), $^{93}$Mo($\gamma$,n) and $^{90}$Zr($\gamma$,n) cross section measurements carried out using real photons at the HIGS/TUNL facility. The overarching physics motivation for these experimental investigations is to advance knowledge on a forefront topic in nuclear astrophysics – the nucleosynthesis beyond Fe of the rarest...
In this talk, I will show the SIMPLE python code we have developed and its capabilities. The code allows us to use 6 different sets of core-collapse supernova model sets with 15, 20 and 25 solar mass progenitors in order to compare the nucleosynthesis process data from the simulated supernova models with the isotope ratios measured from meteorites. The main objective of the code is to help...
Photonuclear reactions are critical in p-process nucleosynthesis, which produces rare proton-rich isotopes (p-nuclei) through γ-induced reactions like (γ, n), (γ, p), and (γ, α). These reactions occur at temperatures from 1.5 to 3.5 GK, typically in explosive environments such as ty-pe II or type Ia supernovae. Theoretical estimates of p-nuclei nucleosynthesis are uncertain, requiring accurate...
The heavier p-isotopes can be produced through the $\gamma$-process, which involves a complicated reaction network. In this nucleosynthesis process ($\gamma$,$\alpha$) reactions play a key role. To calculate such a reaction network, many input parameters are essential. One of these is the $\alpha$-nucleus optical model potential (AOMP), which describes the interaction between the $\alpha$...
Massive stars are thought to experience p-process nucleosynthesis when they explode as supernovae (and during their last hydrostatic burning stages to a smaller extent). Thanks to the mixing induced by rotational instabilities, rotating massive stars can experience an enhanced s-process during the core helium-burning phase. This can significantly affect the subsequent p-process during their...
The astrophysical p-process is crucial for the synthesis of proton-rich isotopes (p-nuclei) that cannot be formed via the s-process or r-process. Occurring primarily in supernovae, this process involves photodisintegration reactions like (γ, n), (γ, p) and (γ, α), driven by high-energy gamma photons, (p, γ) reactions are also relevant in this context. Recent experimental advances, including...
Study of the isotopic compositions of meteorites and their variations has revealed signatures that can be related to processes of nucleosynthesis in stars. Generally, the size of variations scales inversely with the size of the phases that show such “anomalies”. For the small effects seen in “bulk” it is not always trivial distinguishing astrophysical variations from such of more mundane...
Some of the largest nuclear physics uncertainties in p-process nucleosynthesis stem from the $\alpha$-optical model potential ($\alpha$-OMP). Especially, at high masses the available $\alpha$-OMPs often fail to accurately reproduce experimental results [1]. If the $\alpha$-emission probability in a photodisintegration reaction is comparable to the emission probabilities for other particles,...
I will discuss recent simulation results of neutrino-driven supernova explosions launched from a low-mass 9.6 solar mass iron-core progenitors of low metalicity. The supernova simulations are based on general relativistic neutrino radiation hydrodynamics in spherical symmetry featuring six-species Boltzmann neutrino transport and a complete set of neutrino opacities. Special emphasis is...
One of the questions of heavy element nucleosynthesis associated with massive star explosions will be discussed in this talk, namely the realization of possible conditions enabling neutron capture processes. It depends sensitively on the neutrino fluxes and spectra as well as their evolution, which, in turn are determined by the treatment of neutrino transport in the supernova models. It is...
In massive-star binary systems, upon reaching later stages of stellar evolution one star can expand as a giant and envelope its companion in what is called a common envelope phase. The enveloped companion, here a neutron star, begins to accrete matter. The angular momentum of the accreting material results in the formation of an accretion disk. Accretion of hydrogen rich onto...
The High EffiCiency TOtal absorption spectrometeR (HECTOR) is a summing spectrometer comprised of 16 NaI(Tl) segmented crystals with 2 PMTs on each segment to allow for optimal light collection from incident $\gamma$-rays. The arrangement of the 16 NaI(Tl) crystals allows for almost total 4$\pi$ angular coverage to capture and sum together all $\gamma$-rays following the dexcitation of the...
Several species of short-lived radioactive nuclei (SLRs) are known to have been present in the early solar system (ESS). They are a valuable source of our knowledge of our solar system's formation and early history. Here, we present the latest results from the ERC RADIOSTAR project in a representation usually used in cosmochemistry, where the abundances of SLRs in the early solar system,...
Charge-Exchange (CE) reactions are an important tool for studying the spin-isopin response of nuclei. They can be utilized to obtain information about interactions mediated by the weak nuclear force, such as β and electron capture decay. Using the proportionality between Gamow-Teller strength (B(GT)) and the CE differential cross section, B(GT) distributions can be extracted indirectly. Since...
Thirty years ago, the pioneering experiment on $^{44}$Sm($\alpha$,$\gamma$)$^{148}$Gd by Somorjai $et$ $al.$ [1] (discussed first at a workshop in Budapest in 1994) showed that the prediction of astrophysical reaction rates of $\alpha$-induced reactions is very uncertain. The $\alpha$-nucleus potential (AOMP) was realized as the main source of the wide range of predictions. Only a few years...
Presolar stardust grains, bona-fide particles that formed in the death throes of dying stars and can today be extracted from meteorites, allow us to probe their parent star's isotopic composition. These grains are the sole messenger for directly probing the isotopic composition of the proton-rich isotopes associated with the p-process(es), since these isotopes generally only make up a minute...
