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We investigate the dynamics and evolution of coalescing neutron stars. The three-dimensional Newtonian equations of hydrodynamics are integrated by the `Piecewise Parabolic Method' However, we do include the effects of the emission of…

Astrophysics · Physics 2016-08-30 M. Ruffert , H. -Th. Janka , W. Keil , G. Schaefer

We present our past and current long-term monitoring program of water masers in the circumstellar envelopes of evolved stars, augmented by occasional interferometric observations. Using as example the Mira-variable U Her, we identify three…

Astrophysics of Galaxies · Physics 2024-02-05 Jan Brand , Dieter Engels , Anders Winnberg

Parameter regions in which stars can become pulsationally unstable are found throughout the Hertzsprung-Russel diagram. Stars of high, intermediate, low and very low masses may cross various instability regions along their paths of…

Solar and Stellar Astrophysics · Physics 2015-06-11 Sonja Schuh

The space of density matrices is embedded in a Euclidean space to deduce the dynamical equation satisfied by the state of an open quantum system. The Euclidean norm is used to obtain an explicit expression for the speed of the evolution of…

Quantum Physics · Physics 2019-12-04 Dorje C Brody , Bradley Longstaff

The present work investigates the numerical evolution of linearized oscillations of non-rotating, spherically symmetric neutron stars within the framework of general relativity. We derive the appropriate equations using the (3+1)-formalism.…

General Relativity and Quantum Cosmology · Physics 2007-05-23 Johannes Ruoff

We present a new hydro code based on spectral methods using spherical coordinates. The first version of this code aims at studying time evolution of inertial modes in slowly rotating neutron stars. In this article, we introduce the…

General Relativity and Quantum Cosmology · Physics 2009-11-07 L. Villain , S. Bonazzola

The excitation of the axial quasi-normal modes of a relativistic star by scattered particles is studied by evolving the time dependent perturbation equations. This work is the first step towards the understanding of more complicated…

General Relativity and Quantum Cosmology · Physics 2009-10-31 V. Ferrari , K. D. Kokkotas

Evolved stars dominate galactic spectra, enrich the galactic medium, expand to change their planetary systems, eject winds of a complex nature, produce spectacular nebulae and illuminate them, and transfer material between binary…

We employ an approximate treatment of dissipative hydrodynamics in three dimensions to study the coalescence of binary neutron stars driven by the emission of gravitational waves. The stars are modeled as compressible ellipsoids obeying a…

Astrophysics · Physics 2009-10-22 Dong Lai , Stu Shapiro

This paper is the first in a series aimed at understanding the long-term evolution of neutron star magnetic fields. We model the stellar matter as an electrically neutral and lightly ionized plasma composed of three moving particle species:…

Astrophysics · Physics 2009-11-13 J. Hoyos , A. Reisenegger , J. A. Valdivia

A general relativistic version of the Euler equation for perfect fluid hydrodynamics is applied to a system of two neutron stars orbiting each other. In the quasi-equilibrium phase of the evolution of this system, a first integral of motion…

General Relativity and Quantum Cosmology · Physics 2009-10-30 S. Bonazzola , E. Gourgoulhon , J. -A. Marck

Recent calculations indicate that in the outer parts of neutron stars nuclei are rod-like or slab-like, rather than roughly spherical. We consider the elastic properties of these phases, and argue that they behave as liquid crystals, rather…

Astrophysics · Physics 2009-10-30 C. J. Pethick , A. Y. Potekhin

The universal relations in neutron stars form an essential entity to understand their properties. The moment of inertia, dimensionless tidal deformability, mass quadrupole moment, and oscillation modes are some of the properties that have…

High Energy Astrophysical Phenomena · Physics 2025-08-13 Sagnik Chatterjee , Kamal Krishna Nath

We construct the first dynamically stable ergostars (equilibrium neutron stars that contain an ergoregion) for a compressible, causal equation of state. We demonstrate their stability by evolving both strict and perturbed equilibrium…

General Relativity and Quantum Cosmology · Physics 2019-12-11 Antonios Tsokaros , Milton Ruiz , Lunan Sun , Stuart L. Shapiro , Kōji Uryū

Under the hydrodynamic equilibrium Buchdahl's conditions on the behavior of the density and the pressure, for regular fluid static circularly symmetric star in (2 + 1) dimensions in the presence of a cosmological constant, is established…

General Relativity and Quantum Cosmology · Physics 2014-12-19 Alberto A. Garcia Diaz

The purpose of these notes is to give a brief review of superfluidity in neutron stars. After a short presentation explaining why and how superfluidity is expected in the crust and core of neutron stars, consequences on thermal evolution…

Astrophysics · Physics 2007-05-23 David Langlois

This is the second in a series of papers on the construction and validation of a three-dimensional code for the solution of the coupled system of the Einstein equations and of the general relativistic hydrodynamic equations, and on the…

General Relativity and Quantum Cosmology · Physics 2009-11-07 J. Font , T. Goodale , S. Iyer , M. Miller , L. Rezzolla , E. Seidel , N. Stergioulas , W. Suen , M. Tobias

Hierarchical triple stars are ideal laboratories for studying the interplay between orbital dynamics and stellar evolution. Both stellar wind mass loss and three-body dynamics cooperate to destabilise triples, which can lead to a variety of…

Solar and Stellar Astrophysics · Physics 2022-05-11 S. Toonen , T. C. N. Boekholt , S. Portegies Zwart

Differential equations are derived which show how generalized Euler vector representations of the Euler rotation axis and angle for a rigid body evolve in time; the Euler vector is also known as a rotation vector or axis-angle vector. The…

Mathematical Physics · Physics 2024-12-11 John H. Elton , John R. Elton

The hand-eye measurements have recently been proven to be very efficient for spacecraft attitude determination relative to an ellipsoidal asteroid. However, recent method does not guarantee full attitude observability for all conditions.…

Systems and Control · Electrical Eng. & Systems 2020-03-26 Jin Wu