496 research outputs found
Testing the role of SNe Ia for galactic chemical evolution of p-nuclei with two-dimensional models and with s-process seeds at different metallicities
Date of Acceptance: 07/11/2014The bulk of p isotopes is created in the "gamma processes" mainly by sequences of photodisintegrations and beta decays in explosive conditions in Type Ia supernovae (SNIa) or in core collapse supernovae (ccSN). The contribution of different stellar sources to the observed distribution of p-nuclei in the solar system is still under debate. We explore single degenerate Type Ia supernovae in the framework of two-dimensional SNIa delayed-detonation explosion models. Travaglio et al. discussed the sensitivity of p-nuclei production to different SNIa models, i.e., delayed detonations of different strength, deflagrations, and the dependence on selected s-process seed distributions. Here we present a detailed study of p-process nucleosynthesis occurring in SNIa with s-process seeds at different metallicities. Based on the delayed-detonation model DDT-a of TRV11, we analyze the dependence of p-nucleosynthesis on the s-seed distribution obtained from different strengths of the 13C pocket. We also demonstrate that 208Pb seed alone changes the p-nuclei production considerably. The heavy-s seeds (140 ≤A < 208) contribute with about 30%-40% to the total light-p nuclei production up to 132Ba (with the exception of 94Mo and 130Ba, to which the heavy-s seeds contribute with about 15% only). Using a Galactic chemical evolution code from Travaglio et al., we study the contribution of SNIa to the solar stable p-nuclei. We find that explosions of Chandrasekhar-mass single degenerate systems produce a large amount of p-nuclei in our Galaxy, both in the range of light (A ≤ 120) and heavy p-nuclei, at almost flat average production factors (within a factor of about three). We discussed in details p-isotopes such as 94Mo with a behavior diverging from the average, which we attribute to uncertainties in the nuclear data or in SNIa modeling. Li et al. find that about 70% of all SNeIa are normal events. If these are explained in the framework of explosions of Chandrasekhar-mass white dwarfs resulting from the single-degenerate progenitor channel, we find that they are responsible for at least 50% of the p-nuclei abundances in the solar system.Peer reviewedFinal Accepted Versio
-Process simulations with a modified reaction library
We have performed -process simulations with the most recent stellar
cross sections from the "Karlsruhe Astrophysical Database of
Nucleosynthesis in Stars" project (version v0.2,
http://nuclear-astrophysics.fzk.de/kadonis). The simulations were carried out
with a parametrized supernova type II shock front model (`` process'')
of a 25 solar mass star and compared to recently published results. A decrease
in the normalized overproduction factor could be attributed to lower cross
sections of a significant fraction of seed nuclei located in the Bi and Pb
region around the =126 shell closure.Comment: 5 pages, 1 figure Proceedings "Nuclear Physics in Astrophysics
NPA-III", Dresden/Germany (2007
Type Ia Supernovae as Sites of p-process: Two-Dimensional Models Coupled to Nucleosynthesis
We explore SNe Ia as p-process sites in the framework of two-dimensional SN
Ia delayed detonation and pure deflagration models. The WD precursor is assumed
to have reached the Chandrasekhar mass in a binary system by mass accretion
from a giant/main sequence companion. We use enhanced s-seed distributions,
obtained from a sequence of thermal pulse instabilities both in the AGB phase
and in the accreted material. We apply the tracer-particle method to
reconstruct the nucleosynthesis by the thermal histories of Lagrangian
particles, passively advected in the hydrodynamic calculations. For each
particle we follow the explosive nucleosynthesis with a detailed network for
all isotopes up to 209Bi. We find that SNe Ia can produce a large amount of
p-nuclei, both the light p-nuclei below A=120 and the heavy-p nuclei, at quite
flat average production factors, tightly related to the s-process seed
distribution. For the first time, we find a stellar source able to produce
both, light and heavy p-nuclei almost at the same level as 56Fe, including the
very debated neutron magic 92,94Mo and 96,98Ru. We also find that there is an
important contribution from p-process nucleosynthesis to the s-only nuclei
80Kr, 86Sr, to the neutron magic 90Zr, and to the neutron-rich 96Zr. Finally,
we investigate the metallicity effect on p-process. Starting with different
s-process seed distributions, for two metallicities Z = 0.02 and Z = 0.001,
running SNe Ia models with different initial composition, we estimate that SNe
Ia can contribute to, at least, 50% of the solar p-process composition.Comment: 62 pages, 14 figures, 5 tables, ApJ in pres
Radiogenic p-isotopes from type Ia supernova, nuclear physics uncertainties, and galactic chemical evolution compared with values in primitive meteorites
The nucleosynthesis of proton-rich isotopes is calculated for multi-dimensional Chandrasekhar-mass models of Type Ia supernovae (SNe Ia) with different metallicities. The predicted abundances of the short-lived radioactive isotopes 92Nb, 97, 98Tc, and 146Sm are given in this framework. The abundance seeds are obtained by calculating s-process nucleosynthesis in the material accreted onto a carbon-oxygen white dwarf from a binary companion. A fine grid of s-seeds at different metallicities and 13C-pocket efficiencies is considered. A galactic chemical evolution model is used to predict the contribution of SN Ia to the solar system p-nuclei composition measured in meteorites. Nuclear physics uncertainties are critical to determine the role of SNe Ia in the production of 92Nb and 146Sm. We find that, if standard Chandrasekhar-mass SNe Ia are at least 50% of all SN Ia, they are strong candidates for reproducing the radiogenic p-process signature observed in meteorites.Peer reviewedFinal Accepted Versio
Guidelines for farmers, transporters and official veterinarians to assess the fitness for transport and slaughter of slaughter pigs
Legislative provisions related to animal transport and ante-mortem meat inspection of farm animals exist both at national and at European level. The Regulation (EC) No. 1/2005 characterizes the transport criteria that are to be met with regard to the animals’ health and welfare
Integrating Generative Artificial Intelligence in Intelligent Vehicle Systems
This paper aims to serve as a comprehensive guide for researchers and
practitioners, offering insights into the current state, potential
applications, and future research directions for generative artificial
intelligence and foundation models within the context of intelligent vehicles.
As the automotive industry progressively integrates AI, generative artificial
intelligence technologies hold the potential to revolutionize user
interactions, delivering more immersive, intuitive, and personalised in-car
experiences. We provide an overview of current applications of generative
artificial intelligence in the automotive domain, emphasizing speech, audio,
vision, and multimodal interactions. We subsequently outline critical future
research areas, including domain adaptability, alignment, multimodal
integration and others, as well as, address the challenges and risks associated
with ethics. By fostering collaboration and addressing these research areas,
generative artificial intelligence can unlock its full potential, transforming
the driving experience and shaping the future of intelligent vehicles.Comment: under revie
Selective laser ionization of N 82 indium isotopes: the new r-process nuclide In
Production yields and beta-decay half-lives of very neutron-rich indium isotopes were determined at CERN/ISOLDE using isobaric selectivity of a resonance-ionization laser ion-source. Beta-delayed neutron multiscaling measurements have yielded improved half-lives for 206(6)~ms In, 165(3)~ms In and 141(5)~ms In. With 92(10)~ms In, a new r-process nuclide has been identified which acts as an important `waiting-point' in the In isotopic chain for neutron densities in the range n--10 n/cm, where the r-matter flow has already passed the abundance-peak region
The s Process: Nuclear Physics, Stellar Models, Observations
Nucleosynthesis in the s process takes place in the He burning layers of low
mass AGB stars and during the He and C burning phases of massive stars. The s
process contributes about half of the element abundances between Cu and Bi in
solar system material. Depending on stellar mass and metallicity the resulting
s-abundance patterns exhibit characteristic features, which provide
comprehensive information for our understanding of the stellar life cycle and
for the chemical evolution of galaxies. The rapidly growing body of detailed
abundance observations, in particular for AGB and post-AGB stars, for objects
in binary systems, and for the very faint metal-poor population represents
exciting challenges and constraints for stellar model calculations. Based on
updated and improved nuclear physics data for the s-process reaction network,
current models are aiming at ab initio solution for the stellar physics related
to convection and mixing processes. Progress in the intimately related areas of
observations, nuclear and atomic physics, and stellar modeling is reviewed and
the corresponding interplay is illustrated by the general abundance patterns of
the elements beyond iron and by the effect of sensitive branching points along
the s-process path. The strong variations of the s-process efficiency with
metallicity bear also interesting consequences for Galactic chemical evolution.Comment: 53 pages, 20 figures, 3 tables; Reviews of Modern Physics, accepte
Determination of the stellar (n,gamma) cross section of 40Ca with accelerator mass spectrometry
The stellar (n,gamma) cross section of 40Ca at kT=25 keV has been measured
with a combination of the activation technique and accelerator mass
spectrometry (AMS). This combination is required when direct off-line counting
of the produced activity is compromised by the long half-life and/or missing
gamma-ray transitions. The neutron activations were performed at the Karlsruhe
Van de Graaff accelerator using the quasistellar neutron spectrum of kT=25 keV
produced by the 7Li(p,n)7Be reaction. The subsequent AMS measurements were
carried out at the Vienna Environmental Research Accelerator (VERA) with a 3 MV
tandem accelerator. The doubly magic 40Ca is a bottle-neck isotope in
incomplete silicon burning, and its neutron capture cross section determines
the amount of leakage, thus impacting on the eventual production of iron group
elements. Because of its high abundance, 40Ca can also play a secondary role as
"neutron poison" for the s-process. Previous determinations of this value at
stellar energies were based on time-of-flight measurements. Our method uses an
independent approach, and yields for the Maxwellian-averaged cross section at
kT=30 keV a value of 30 keV= 5.73+/-0.34 mb.Comment: 8 pages, 3 figure
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