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We present our study of stability of differentially rotating, axisymmetric neutron stars described by a polytropic equation of state with $\Gamma = 2$. We focus on quasi-toroidal solutions with a degree of differential rotation $\widetilde…

High Energy Astrophysical Phenomena · Physics 2024-02-29 Paweł Szewczyk , Dorota Gondek-Rosińska , Pablo Cerdá-Durán

We investigate the structure of self-gravitating polytropic stellar systems. We present a method which allows to obtain approximate analytical solutions, $\psi_{n+\epsilon}({\bf x})$, of the nonlinear Poisson equation with the polytropic…

Astrophysics · Physics 2009-10-31 Mikhail V. Medvedev , George Rybicki

We have developed a new numerical scheme to obtain quasiequilibrium structures of nonaxisymmetric compact stars such as binary neutron star systems as well as the spacetime around those systems in general relativity. Concerning…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Fumihiko Usui , Koji Uryu , Yoshiharu Eriguchi

Fragmentation of highly differentially rotating massive stars that undergo collapse has been suggested as a possible channel for binary black hole formation. Such a scenario could explain the formation of the new population of massive black…

High Energy Astrophysical Phenomena · Physics 2019-04-09 Lunan Sun , Milton Ruiz , Stuart L. Shapiro

A recipe is presented to construct an analytic, self-consistent model of a non-barotropic neutron star with a poloidal-toroidal field of arbitrary multipole order, whose toroidal component is confined in a torus around the neutral curve…

High Energy Astrophysical Phenomena · Physics 2015-01-26 Alpha Mastrano , Arthur George Suvorov , Andrew Melatos

We study the effects of anisotropic pressure on the properties of spherically symmetric, gravitationally bound objects. We consider the full general relativistic treatment of this problem and obtain exact solutions for various form of…

Astrophysics · Physics 2007-05-23 Krsna Dev , Marcelo Gleiser

We investigate the effect of the anisotropy of a harmonic trap on the behaviour of a fast rotating Bose-Einstein condensate. This is done in the framework of the 2D Gross-Pitaevskii equation and requires a symplectic reduction of the…

Analysis of PDEs · Mathematics 2008-12-01 Amandine Aftalion , Xavier Blanc , Nicolas Lerner

The internal rotation of low mass stars all along their evolution is of primary interest when studying their rotational dynamics, internal mixing and magnetic fields generation. In this context, helio- and asteroseismology probe angular…

Solar and Stellar Astrophysics · Physics 2016-09-05 Delphine Hypolite , Stéphane Mathis , Michel Rieutord

The influence of rotation on the dynamical evolution of collisional stellar systems is investigated by solving the orbit-averaged Fokker-Planck equation in (E,J_z)-space. We find that large amounts of initial rotation drive the system into…

Astrophysics · Physics 2007-05-23 Ch. Einsel , R. Spurzem

We present preliminary results on a new family of distribution functions that are able to generate axisymmetric, truncated (i.e., finite size) stellar dynamical models characterized by toroidal shapes. The relevant distribution functions…

Astrophysics · Physics 2009-11-10 L. Ciotti , G. Bertin , P. Londrillo

Either bulk rotation or local turbulence is widely invoked to drive fragmentation in collapsing cores so as to produce multiple star systems. Even when the two mechanisms predict different manners in which the stellar spins and orbits are…

Solar and Stellar Astrophysics · Physics 2016-08-17 Jeremy Lim , Paul K. H. Yeung , Tomoyuki Hanawa , Shigehisa Takakuwa , Tomoaki Matsumoto , Kazuya Saigo

We investigate the effects of the purely toroidal magnetic field on the equilibrium structures of the relativistic stars. The master equations for obtaining equilibrium solutions of relativistic rotating stars containing purely toroidal…

Astrophysics · Physics 2008-11-26 Kenta Kiuchi , Shijun Yoshida

Galactic nuclei, the densest stellar environments in the Universe, exhibit a complex geometrical structure. The stars orbiting the central supermassive black hole follow a mass segregated distribution both in the radial distance from the…

Astrophysics of Galaxies · Physics 2023-10-24 Hanxi Wang , Bence Kocsis

In this paper, we consider isotropic solution and extend it to two different exact well-behaved spherical anisotropic solutions through minimal geometric deformation method in $f(R,T,R_{\rho\eta}T^{\rho\eta})$ gravity. We only deform the…

General Relativity and Quantum Cosmology · Physics 2024-04-03 Tayyab Naseer , M. Sharif

Globular clusters are dense stellar systems whose core slowly contracts under the effect of self-gravity. The rate of this process was recently found to be directly linked to the initial amount of velocity anisotropy: tangentially…

Astrophysics of Galaxies · Physics 2022-06-01 Kerwann Tep , Jean-Baptiste Fouvry , Christophe Pichon

A rotating bosonic many-body system in a harmonic trap is studied with the 3D-Cranked Hartree-Fock-Bogoliubov method at zero temperature, which has been applied to nuclear many-body systems at high spin. This method is a variational method…

Other Condensed Matter · Physics 2009-11-13 Nobukuni Hamamoto , Makito Oi , Naoki Onishi

We present a new, simple, fast algorithm to numerically evolve disks of inelastically colliding particles surrounding a central star. Our algorithm adds negligible computational cost to the fastest existing collisionless N-body codes, and…

Astrophysics · Physics 2008-11-26 Yoram Lithwick , Eugene Chiang

We have computed models of rotating relativistic stars with a toroidal magnetic field and investigated the combined effects of magnetic field and rotation on the apparent shape (i.e. the surface deformation), which could be relevant for the…

General Relativity and Quantum Cosmology · Physics 2014-02-14 Joachim Frieben , Luciano Rezzolla

Our focus is to study constellations of disjoint disks in the hyperbolic space, the unit disk equipped with the hyperbolic metric. Each constellation corresponds to a set $E$ which is the union of $m>2$ disks with hyperbolic radii $r_j>0,…

Complex Variables · Mathematics 2023-11-30 Harri Hakula , Mohamed M. S. Nasser , Matti Vuorinen

We construct spherical, hydrostatic models of dense molecular cores and Bok globules consisting of two distinct, spatially separate gas components: a central, isothermal region surrounded by a negative-index, polytropic envelope. The clouds…

Astrophysics · Physics 2009-10-31 Charles L. Curry , Christopher F. McKee