Astrophysical models of r-process nucleosynthesis an update

After tf, thermodynamic variables are evolved following the prescription in Fujimoto et al. It has been related to neutrino emission from the hot collapsed core and accreted matter Betheand this regular scenario is again becoming more and more promising with recent multi-D hydrodynamic approaches and improved spectral neutrino transport e.

The r-process contributes to the abundances of the heaviest four isotopes Xe, Xe, Xe and Xe and is totally responsible for the heaviest two of those. Therefore, we present two different nucleosynthesis calculations: That sequence could also begin earlier in galactic time than would s-process nucleosynthesis; so each scenario fits the earlier growth of r-process abundances in the galaxy.

For the post-processing we only consider gravitationally unbound tracer particles see Section 2. There are additional shortcomings in the treatment presented here.

Standard image High-resolution image Export PowerPoint slide 5. Note that the "contact" interface of the asymmetric merger is different from the symmetric case. Otherwise they would dim quickly. This includes that thermodynamic properties of tracer particles are only extrapolated beyond the end of the MHD calculation and the nucleosynthesis results were not yet tested with several nuclear mass models.

In this second approach, we post-process the data from the tracer and use the neutrino information obtained with the leakage scheme Section 2.

Primary stellar nucleosynthesis begins earlier in the galaxy than does secondary nucleosynthesis.

Astrophysics > Solar and Stellar Astrophysics

Some recent studies, which include the fact that our Galaxy possibly results from smaller merging subsystems with different star formation rateshave been expected to show a way out of this dilemma.

We use integrated neutrino luminosities to update the electron fraction outside the neutrinosphere neglecting the effect of neutrino energy deposition on the matter temperature.

Although the model provides profiles for rotation and magnetic fields, we use an analytic prescription for their distributions and we will comment on this choice in Section 4.

Standard image High-resolution image Export PowerPoint slide 4. Clayton[7] who found that no single temporal snapshot matched the solar r-process abundances, but, that when superposed, did achieve a successful characterization of the r-process abundance distribution.

Fowler and Donald D. This trend is confirmed also by the network for T 10 GK. They record the thermodynamic conditions of a particular fluid element and serve as input to the post-processing nucleosynthesis calculations. The present Letter has the aim of exploring the results from our 3D magnetohydrodynamic MHD calculations, which lead to bipolar jet ejection.

Ye for the original simulation without neutrino captures green and including a simplified prescription for neutrino heating red. After tf, thermodynamic variables are evolved following the prescription in Fujimoto et al. For this reason, in the asymmetric system the contact region preferentially contributes to ejecta with low initial densities.

Confirming relevance to the r-process is that it is radiogenic power from radioactive decay of r-process nuclei that maintains the visibility of these spun off r-process fragments.

The major outcome was that high rotation rates and possibly unrealistically high magnetic fields were required to launch explosions.

Astrophysics > Solar and Stellar Astrophysics

The n, 2n rates are estimated with the TALYS code and the reverse rates from detailed balance expressions. The neutron-capture flow must therefore wait for beta decay at those so-called waiting points, which therefore grow larger in abundance similar to water in a dammed up river.

Electron-capture supernovae, which explode without a long phase of accretion onto the proto-neutron star PNSapparently provide more favorable conditions Wanajo et al. For those hitherto unexplained abundance peaks, which are approximately 10 u lighter than the s-process abundance peaks, to be created by rapid neutron capture implied that other neutron-rich nuclei would also be synthesized by the same process.

Note that the improvements in the electron fraction calculation result only in minor variations of the abundances. History[ edit ] The need for a physical setting providing rapid capture of neutrons was seen from the relative abundances of isotopes of heavy chemical elements given in a table of abundances by Hans Suess and Harold Urey in The ejected material must be relatively neutron-rich, a condition which has been difficult to achieve in models, [4] so that astrophysicists remain uneasy about their adequacy for successful r-process yields Entirely new astronomical data about the r process was discovered in when the LIGO and Virgo gravitational-wave observatories discovered a merger of two neutron stars.

In order to obtain mass integrated abundances we distribute the total ejected mass equally among all ejected tracers.

Standard image High-resolution image Export PowerPoint slide The final mass-integrated ejecta composition is shown in Figure 4. Consequently, strongly magnetized regions appear near the rotational axis with an associated magnetic pressure quickly reaching and exceeding that of the local gas pressure.

However, the agreement is not equally good for all mass numbers as the nuclei between peaks are slightly underproduced. Their nucleosynthesis, however, exhibits extreme sensitivity to the detailed conditions in the ejecta, whose viability for strong r-processing could not be verified by sophisticated hydrodynamical models e.

Representation of dominant fission regions in the N, Z plane. The locations are given in the projection on the orbital plane at the time when the stellar collision begins. The computed model then undergoes gravitational collapse and experiences core-bounce due to the stiffening of the EoS above nuclear saturation density.

Abstract: An update on astrophysical models for nucleosynthesis via rapid neutron capture, the r process, is given. A neutrino-induced r process in supernova helium shells may have operated up to metallicities of ~10^-3 times the solar value.

Another r-process source, possibly neutron star mergers, is required for higher metallicities. Astrophysical robustness of the r-process nucleosynthesis Oleg Korobkin Stockholm University, Oskar Klein Centre, Sweden September 9, O. Korobkin robustness of the r-process in neutron star mergers September 9, 1 / An update on astrophysical models for nucleosynthesis via rapid neutron capture, the r process, is given.

A neutrino-induced r process in supernova helium shells may have operated up to metallicities of ~10^-3 times the solar value. Another r-process source, possibly neutron star mergers, is. The r-process typically synthesizes new nuclei of the heaviest four isotopes of any heavy element, being totally responsible for the abundances of its two heaviest isotopes, which are referred to as r-only nuclei.

We present a large survey of r-process nucleosynthesis models. The parameters varied are the initial electron-to-baryon ratio, Y e, the entropy per baryon, s, and the dynamical timescale, τ 0.

These quantities usefully characterize the abundances expected from any explosive event. An update on astrophysical models for nucleosynthesis via rapid neutron capture, the r process, is given.

A neutrino-induced r process in supernova helium shells may have operated up to metallicities of ∼ 10 −3 times the solar value.

Another r-process source, possibly neutron .

Astrophysical models of r-process nucleosynthesis an update
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r-PROCESS NUCLEOSYNTHESIS IN DYNAMICALLY EJECTED MATTER OF NEUTRON STAR MERGERS - IOPscience