EMMI workshop: Neutron Matter in Astrophysics: From Neutron Stars to the r-Process

Neutron-capture elements often are extremely overabundant in metal-poor halo stars. In some cases we have been able to determine accurate abundances or significant upper limits to over 30 elements with Z>30. These detailed abundance distributions can provide significant constraints on neutron- capture nucleosynthesis predictions. But how well do we really know the neutron-capture...

Observations of elemental abundances in metal-poor stars in the Galactic halo and dwarf galaxies are used to shed light on the stellar sources for the elements (1) from Na to Zn, (2) from Sr to Ag, and (3) from Ba to U. The production of Sr, Y, and Zr in the neutrino-driven winds from nascent neutron stars provides a key insight into the diverse sources operating in the early universe. It is...

Observations indicate that r-process elements have at least two components. The heavy r-process nuclei (A>130) are synthesized by rapid neutron capture in a yet unknown site. The second component corresponds to the lighter element primary process (LEPP) or weak r-process. Our nucleosynthesis studies are based on hydrodynamical simulations for core-collapse supernovae and their subsequent...

Recent observations of thermal emissions from quiescent and isolated cooling neutron stars and of photospheric radius expansions in X-ray bursters can be used to estimate their masses and radii. Although the observational uncertainties for each source are considerable, they can be used to snugly constrain the mass-radius relation if it is assumed that a single such relation fits all neutron...

This talk will discuss the impact of chiral three-nucleon forces on neutron-rich nuclei and on neutron-rich matter. I will show that three-nucleon forces lead to repulsive contributions to the interactions among valence neutrons that change the location of the neutron drip line from 28O to the experimentally observed 24O. This three-nucleon mechanism provides the first microscopic explanation...

Thermodynamical properties and the composition of nuclear matter are strongly affected by correlations, in particular the formation of clusters. At very low densities and finite temperatures the system can be described by the virial equation of state that is based on experimental data. With increasing density medium effects become important that modify the properties of the clusters. At...

We perform a systematic analysis of the density dependence of nuclear symmetry energy within the microscopic Brueckner-Hartree-Fock (BHF) approach using the realistic Argonne V18 nucleon-nucleon potential plus a phenomenological three-body force of Urbana type. Our results are compared thoroughly with those arising from several Skyrme and relativistic effective models. The values of the...

The properties of exotic nuclei are ideally studied in inverse-kinematics experiments at high beam energies using the FRS-LAND facilities at GSI, allowing exclusive measurements of all projectile-like residues following the electromagnetic excitation of the projectile in a high-Z target (Pb). At beam energies of ~500 AMeV electromagnetic excitations are dominated by dipole...

It is important, both for nuclear structure physics and understanding the synthesis of heavy elements in the cosmos, to determine how single-particle states change as we move away from the valley of stability, especially around shell closures. One powerful method to probe single-particle structure of nuclei is to use single-nucleon transfer reactions. With short-lived exotic nuclei, these...

Recent experiments with stored exotic nuclei, that have been performed at the Experimental Storage Ring ESR in Darmstadt, Germany, will be discussed in this contribution. Broad-band Schottky (SMS) and Isochronous (IMS) mass spectrometry are extremely powerful methods for simultaneous measurements of big numbers of nuclear masses in one experiment. The former method is applied to...

We investigate r-process nucleosynthesis during magneto-hydrodynamic supernova explosions driven by rapid rotations and strong magnetic fields. These types of supernovae are very important not only for magnetar formation sites, but also for astronomical r-process sites in astrophysics. Our r-process nucleosynthesis simulations are based on the astronomical supernova explosion models, which...

Although they are but a small fraction of the mass ejected in core-collapse supernovae, neutrino-driven winds (NDWs) from nascent proto-neutron stars (PNSs) have the potential to contribute significantly to supernova nucleosynthesis. In previous works, the NDW has been implicated as a possible source of r-process and light p-process isotopes. I will present time-dependent hydrodynamic...

Core collapse supernovae have long been considered one of the most promising astrophysical sites for r-process nucleosynthesis. Detailed calculations of the neutrino-heated winds from proto-neutron stars, however, find that the ratio of neutrons to seed nuclei is generally too low for the r-process to reach the second or third abundance peaks. Success instead appears to require some...

The abundances of r-process nucleosynthesis in the mass A=130 region are largely affected by the nuclear structure properties around the N=82 magic number. Some simulations show a better description of the abundances if a shell quenching of N=82 is assumed. In addition, the anomalous behavior of the experimental 2+ excitation energies in neutron rich Cd isotopes has been interpreted as an...

Within the Generalized Energy-density Functional method we have systematically calculated the beta-decay total energy releases, half-lives and beta-delayed neutron emission branchings for near-spherical nuclei with charge numbers Z = 60 - 80 near the neutron shell at N = 126. Together with our previous calculations this provides a basic set of the weak rates for the r-process modeling. Our...

Radiation Pressure Acceleration (RPA) with solid state density ion bunches, which are about 1E15 times more dense then classically accelerated ion bunches, allow for a high probability that generated fission products fuse again, when the thorium beam strikes a second close Th target. The fission fragments have a 1/sin(Theta) angular distribution and thus are predominantly emitted in beam...

The rapid neutron-capture process, or r-process, is known to be of fundamental importance for explaining the origin of approximately half of the A>60 stable nuclei observed in nature. In recent years nuclear astrophysicists have developed more and more sophisticated r-process models, eagerly trying to add new astrophysical or nuclear physics ingredients to explain the solar system...

We consider neutrinos and nucleosynthesis in several different environments: supernovae, gamma ray bursts and compact object mergers. We examine the role of neutrinos in the r-process, the p-process and in the formation of Nickel-26. We consider the impact of neutrino general relativistic effects and collective neutrino flavor transformation.

The shear viscosity plays an important role in damping gravitational wave driven instabilities in old and accreting neutron stars. We discuss the shear viscosity in the presence of an antikaon condensate in neutron stars, using Boltzmann kinetic equation in the relaxation time approximation. The calculation of shear viscosity involves the equation of state (EoS) as an input, that we construct...

We extend the hadronic SU(3) non-linear sigma model to include quark degrees of freedom. The choice of potential for the deconfinement order parameter as a function of temperature and chemical potential allows us to construct a realistic phase diagram from the analysis of the order parameters of the system. These parameters are the chiral condensate, for the chiral symmetry restoration, and...

Modern constraints from the mass and mass-radius-relation measurements require stiff EoS at high densities, whereas flow data from heavy-ion collisions seem to disfavour too stiff behavior of the EoS. Our aim is to present a nuclear EoS at supernuclear densities which satisfies both the constraints from neutron star (NS) and the heavy ion collision phenomenology. The data from massive NSs and...

Replaced by D. Blaschke

The thermal evolution of hybrid stars is investigated. The structure and composition of these objects are obtained by means of an exteded hadronic and quark SU(3) non-linear sigma model. Within this model the degrees of freedom of the system change naturally from quarks to hadrons, allowing a more natural description of hybrid stars. In this work we will focus on the thermal evolution of these...

The site of the r-process has been the most enduring mystery in nucleosynthesis theory since the publication of the seminal papers in this field. Of particular promise (in their times and for some even today) have been the many efforts suggesting Type II supernovae as the site with the relevant conditions arising either in or near the exploding core (initially championed by Burbidge et al.),...

Recently we have shown that neutron capture rates on nuclei near stability can significantly influence the r-process abundance pattern. We discuss the different mechanisms by which the abundance pattern is sensitive to the capture rates and identify key nuclei whose rates are of particular importance. We compare the behavior of the system in different astrophysical conditions, e.g. an...