66 research outputs found
Impact of nuclear mass uncertainties on the -process
Nuclear masses play a fundamental role in understanding how the heaviest
elements in the Universe are created in the -process. We predict -process
nucleosynthesis yields using neutron capture and photodissociation rates that
are based on nuclear density functional theory. Using six Skyrme energy density
functionals based on different optimization protocols, we determine for the
first time systematic uncertainty bands -- related to mass modeling -- for
-process abundances in realistic astrophysical scenarios. We find that
features of the underlying microphysics make an imprint on abundances
especially in the vicinity of neutron shell closures: abundance peaks and
troughs are reflected in trends of neutron separation energy. Further advances
in nuclear theory and experiments, when linked to observations, will help in
the understanding of astrophysical conditions in extreme -process sites.Comment: 7 pages, 3 figure
Origin of the elements
What is the origin of the oxygen we breathe, the hydrogen and oxygen (in form of water H2O) in rivers and oceans, the carbon in all organic compounds, the silicon in electronic hardware, the calcium in our bones, the iron in steel, silver and gold in jewels, the rare earths utilized, e.g. in magnets or lasers, lead or lithium in batteries, and also of naturally occurring uranium and plutonium? The answer lies in the skies. Astrophysical environments from the Big Bang to stars and stellar explosions are the cauldrons where all these elements are made. The papers by Burbidge (Rev Mod Phys 29:547–650, 1957) and Cameron (Publ Astron Soc Pac 69:201, 1957), as well as precursors by Bethe, von Weizsäcker, Hoyle, Gamow, and Suess and Urey provided a very basic understanding of the nucleosynthesis processes responsible for their production, combined with nuclear physics input and required environment conditions such as temperature, density and the overall neutron/proton ratio in seed material. Since then a steady stream of nuclear experiments and nuclear structure theory, astrophysical models of the early universe as well as stars and stellar explosions in single and binary stellar systems has led to a deeper understanding. This involved improvements in stellar models, the composition of stellar wind ejecta, the mechanism of core-collapse supernovae as final fate of massive stars, and the transition (as a function of initial stellar mass) from core-collapse supernovae to hypernovae and long duration gamma-ray bursts (accompanied by the formation of a black hole) in case of single star progenitors. Binary stellar systems give rise to nova explosions, X-ray bursts, type Ia supernovae, neutron star, and neutron star–black hole mergers. All of these events (possibly with the exception of X-ray bursts) eject material with an abundance composition unique to the specific event and lead over time to the evolution of elemental (and isotopic) abundances in the galactic gas and their imprint on the next generation of stars. In the present review, we want to give a modern overview of the nucleosynthesis processes involved, their astrophysical sites, and their impact on the evolution of galaxies
Erratum: Progenitor-explosion connection and remnant birth masses for neutrino-driven supernovae of iron-core progenitors (2012, ApJ, 757, 69)
An erroneous interpretation of the hydrodynamical results led to an incorrect
determination of the fallback masses in Ugliano et al. (2012), which also (on a
smaller level) affects the neutron star masses provided in that paper. This
problem was already addressed and corrected in the follow-up works by Ertl et
al. (2015) and Sukhbold et al. (2015). Therefore, the reader is advised to use
the new data of the latter two publications. In the remaining text of this
Erratum we present the differences of the old and new fallback results in
detail and explain the origin of the mistake in the original analysis by
Ugliano et al. (2012).Comment: 3 pages, 2 figures; submitted to The Astrophysical Journa
Neutrino-driven winds in the aftermath of a neutron star merger: nucleosynthesis and electromagnetic transients
We present a comprehensive nucleosynthesis study of the neutrino-driven wind
in the aftermath of a binary neutron star merger. Our focus is the initial
remnant phase when a massive central neutron star is present. Using tracers
from a recent hydrodynamical simulation, we determine total masses and
integrated abundances to characterize the composition of unbound matter. We
find that the nucleosynthetic yields depend sensitively on both the life time
of the massive neutron star and the polar angle. Matter in excess of up to becomes unbound until . Due to
electron fractions of mainly nuclei with mass
numbers are synthesized, complementing the yields from the earlier
dynamic ejecta. Mixing scenarios with these two types of ejecta can explain the
abundance pattern in r-process enriched metal-poor stars. Additionally, we
calculate heating rates for the decay of the freshly produced radioactive
isotopes. The resulting light curve peaks in the blue band after about . Furthermore, high opacities due to heavy r-process nuclei in the dynamic
ejecta lead to a second peak in the infrared after .Comment: 15 pages, 18 figures, 2 tables, accepted by Ap
Core-collapse supernova simulations with reduced nucleosynthesis networks
We present core-collapse supernova simulations including nuclear reaction
networks that impact explosion dynamics and nucleosynthesis. The different
composition treatment can lead to changes in the neutrino heating in the
vicinity of the shock by modifying the number of nucleons and thus the
neutrino-opacity of the region. This reduces the ram pressure outside the shock
and allows an easier expansion. The energy released by the nuclear reactions
during collapse also slows down the accretion and aids the shock expansion. In
addition, nuclear energy generation in the postshocked matter produces up to
more energetic explosions. Nucleosynthesis is affected due to the
different dynamic evolution of the explosion. Our results indicate that the
energy generation from nuclear reactions helps to sustain late outflows from
the vicinity of the proto-neutron star, synthesizing more neutron-rich species.
Furthermore, we show that there are systematic discrepancies between the ejecta
calculated with in-situ and ex-situ reaction networks. These differences stem
from the intrinsic characteristics of evolving the composition in hydrodynamic
simulations or calculating it with Lagrangian tracer particles. The mass
fractions of some Ca, Ti, Cr, and Fe isotopes are consistently underproduced in
postprocessing calculations, leading to different nucleosynthesis paths. Our
results suggest that large in-situ nuclear reaction networks are important for
a realistic feedback of the energy generation, the neutrino heating, and a more
accurate ejecta composition.Comment: Submitted to ApJ. Received 2022 October 20; revised 2023 May 13;
accepted 2023 May 1
Neutrino-driven winds from neutron star merger remnants
We present a detailed, 3D hydrodynamics study of the neutrino-driven winds
that emerge from the remnant of a NS merger. Our simulations are performed with
the Newtonian, Eulerian code FISH, augmented by a detailed, spectral neutrino
leakage scheme that accounts for heating due to neutrino absorption in
optically thin conditions. Consistent with the 2D study of Dessart et al.
(2009), we find that a strong baryonic wind is blown out along the original
binary rotation axis within ms after the merger. We compute a lower limit
on the expelled mass of , large enough to be
relevant for heavy element nucleosynthesis. The physical properties vary
significantly between different wind regions. For example, due to stronger
neutrino irradiation, the polar regions show substantially larger than
those at lower latitudes. This has its bearings on the nucleosynthesis: the
polar ejecta produce interesting r-process contributions from to
about 130, while the more neutron-rich, lower-latitude parts produce also
elements up to the third r-process peak near . We also calculate the
properties of electromagnetic transients that are powered by the radioactivity
in the wind, in addition to the macronova transient that stems from the dynamic
ejecta. The high-latitude (polar) regions produce UV/optical transients
reaching luminosities up to , which peak around 1
day in optical and 0.3 days in bolometric luminosity. The lower-latitude
regions, due to their contamination with high-opacity heavy elements, produce
dimmer and more red signals, peaking after days in optical and
infrared. Our numerical experiments indicate that it will be difficult to infer
the collapse time-scale of the HMNS to a BH based on the wind electromagnetic
transient, at least for collapse time-scales larger than the wind production
time-scale.Comment: 25 pages, 4 tables, 22 figures. Submitted to MNRA
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