scholarly journals Fusion in Space: Nuclear Astrophysics, Neutron Star Mergers, and Accretion Disks

2021 ◽  
Author(s):  
Jonah Miller
Keyword(s):  
Neutron Star ◽  
Accretion Disks ◽  
Nuclear Astrophysics

scholarly journals The Role of Opacities in Accretion Disks

1995 ◽  
Vol 10 ◽  
pp. 597-598
Author(s):  
R. Wehrse
Keyword(s):  
Angular Momentum ◽  
Neutron Star ◽  
Potential Energy ◽  
Accretion Disk ◽  
Accretion Disks ◽  
Heat Generation ◽  
White Dwarf ◽  
Young Stellar Object ◽  
Central Object

An accretion disk is formed when matter with angular momentum is flowing on a gravitating object (as e.g. a white dwarf, a neutron star, a young stellar object, or a black bole). It radiates because the transport of angular momentum (required for the matter to reach the central object) necessarily implies the conversion of potential energy into a form of energy that corresponds to higher entropy. Many aspects of the physics (as e.g. the mechanism for the heat generation) are not yet well understood but they are presently one of the centers of astronomical interest (see e.g. the books by Frank, King, and Raine, 1992, or by Wheeler, 1993).

scholarly journals The Dynamics of Binary Neutron Star Mergers and GW170817

2020 ◽  
Vol 70 (1) ◽  
pp. 95-119 ◽  
Author(s):  
David Radice ◽  
Sebastiano Bernuzzi ◽  
Albino Perego
Keyword(s):  
Neutron Star ◽  
Nuclear Astrophysics ◽  
Theoretical Models ◽  
Physical Processes ◽  
Binary Neutron Star ◽  
Compact Binary ◽  
Open Questions ◽  
Binary Mergers ◽  
R Process ◽  
Process Elements

With the first observation of a binary neutron star merger through gravitational waves and light, GW170817, compact binary mergers have now taken the center stage in nuclear astrophysics. They are thought to be one of the main astrophysical sites of production of r-process elements, and merger observations have become a fundamental tool to constrain the properties of matter. Here, we review our current understanding of the dynamics of neutron star mergers in general and of GW170817 in particular. We discuss the physical processes governing the inspiral, merger, and postmerger evolution, and we highlight the connections between these processes, the dynamics, and the multimessenger observables. Finally, we discuss open questions and issues in the field and the need to address them through a combination of better theoretical models and new observations.

scholarly journals Structure of Strange Quark Matter and Neutron Stars

2004 ◽  
Vol 218 ◽  
pp. 289-296
Author(s):  
James M. Lattimer
Keyword(s):  
Neutron Star ◽  
Symmetry Energy ◽  
Nuclear Physics ◽  
Laboratory Experiments ◽  
Nuclear Astrophysics ◽  
Analytic Solutions ◽  
Strong Interactions ◽  
Skin Thickness ◽  
Neutron Skin ◽  
Global Features

The properties of neutron and strange matter stars are discussed from global and observational perspectives. The global features, i.e., the mass-radius relation, the moment of inertia, and the binding energy, of these objects can be understood by examination of the few known relevant analytic solutions to Einstein's equations. A close connection exists between neutron star radii and the density dependence of the isospin dependence of strong interactions, i.e., the nuclear symmetry energy. Interestingly, a similar relation has been found to exist between the symmetry energy and the neutron skin thickness of neutron-rich nuclei, the object of a new generation of laboratory experiments, although these are 1018 times smaller. Recent observations of neutron star masses and radiation radii are summarized. The status of these observations as predictors of nuclear force properties is examined. The combination of observations, laboratory experiments, and theory is an extremely powerful tool for both nuclear physics and nuclear astrophysics.

scholarly journals Constraints on the astrophysical environment of binaries with gravitational-wave observations

2020 ◽  
Vol 644 ◽  
pp. A147
Author(s):  
Vitor Cardoso ◽  
Andrea Maselli
Keyword(s):  
Black Hole ◽  
Dark Matter ◽  
Neutron Star ◽  
Gravitational Wave ◽  
Accretion Disks ◽  
Environmental Effects ◽  
Surrounding Medium ◽  
Future Generations ◽  
Dynamical Friction ◽  
Compact Binaries

Aims. The dynamics of coalescing compact binaries can be affected by the environment in which the systems evolve, leaving detectable signatures in the emitted gravitational signal. In this paper, we investigate the ability of gravitational-wave detectors to constrain the nature of the environment in which compact binaries merge. Methods. We parametrized a variety of environmental effects by modifying the phase of the gravitational signal emitted by black hole and neutron star binaries. We infer the bounds on such effects by current and future generations of interferometers, studying their dependence on the binary’s parameters. Results. We show that the strong dephasing induced by accretion and dynamical friction can constrain the density of the surrounding medium to orders of magnitude below those of accretion disks. Planned detectors, such as LISA or DECIGO, will be able to probe densities typical of those of dark matter.

scholarly journals In-Medium Strangeness Production and Hyperon-Potentials

2019 ◽  
Vol 26 ◽  
pp. 83
Author(s):  
T. Gaitanos ◽  
A. Violaris ◽  
L. Fabbietti ◽  
M. Steffen ◽  
J. Wirth
Keyword(s):  
Experimental Data ◽  
Neutron Star ◽  
Theoretical Study ◽  
Nuclear Astrophysics ◽  
The Other ◽  
Recent Experimental Data ◽  
Theoretical Treatment ◽  
Kaon Production ◽  
Microscopic Models ◽  
Open Issue

A hot topic of current research concerns the Equation of State (EoS) of nucleons and, in particular, of hyperons in dense nucleonic media. The study of the EoS at nucleon densities far beyond saturation has been initiated several decades ago, however, the behavior of the EoS for strangeness particles is still an open issue. The strangeness part of the EoS is very important not only for the physics of exotic (hyper)nuclei, but also crucial for nuclear astrophysics, e.g., neutron star physics.Here we present our recent investigations related to the theoretical treatment of in-medium hyperon-interactions as well as first preliminary experimental results from pion-induced reactions. The theoretical study is based on the well-established Non-Linear Derivative (NLD) model, which is extended to the strangeness sector via SU(6) symmetry arguments. It turns out that the NLD-predictions are consistent with microscopic models based on the chiral-EFT theory. On the other hand, recent experimental HADES-data on hyperon and kaon production from pion-induced reactions indicate sensitivities on the underlying in-medium hyperon potentials. We thus conclude that, the recent experimental data from pion-induced reactions will definitely set stringent constraints on the still less understood hyperon-potentials in nucleonic matter.

The Contribution of Degenerate Electron Pressure to The Stability of The Outer Region of Thin Keplerian Accretion Disks Around a Neutron Star

2015 ◽  
Vol 11 (1) ◽  
pp. 2886-2891
Author(s):  
Abbi Seyoum Demissie
Keyword(s):  
Neutron Star ◽  
Accretion Disks ◽  
Outer Region ◽  
Thin Disk ◽  
Gas Pressure ◽  
Degenerate Electron ◽  
Small Temperature ◽  
Radial Perturbation ◽  
The Stability ◽  
Definite Temperature

The stability analysis of a geometrically thin, gas-pressure dominated accretion disk around a neutron star is presented. In purely radial perturbation case, thin disk is stable to thermal modes. The stability is analyzed at a small temperature, that is temperature approaching zero and at definite temperature. The contribution of both fully and partially degenerate electrons pressure for the stability of the disk in its outer region is investigated. We find that the disk is stable in this region, where the gas pressure is more dominant than radiation pressure.

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