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We study the main astrophysical properties of differentially rotating neutron stars described as stationary and axisymmetric configurations of a moderately stiff $\Gamma=2$ polytropic fluid. The high level of accuracy and of stability of…

High Energy Astrophysical Phenomena · Physics 2017-03-08 Dorota Gondek-Rosinska , Izabela Kowalska , Loic Villain , Marcus Ansorg , Marcin Kucaba

This article deals with the problem of the motion of stars in galaxies. By using the Newton's theory combined with a gravitational time dilatation for the weak gravitational field, it is possible to give a solution without using the dark…

Cosmology and Nongalactic Astrophysics · Physics 2010-07-22 Emmanuel Moulay

This paper reviews some of the important advances made over the last decade concerning theory of roAp stars.

Astrophysics · Physics 2009-11-13 M. S. Cunha

We investigate whether compact stars having Tolman-like interior geometry admit conformal symmetry. Taking anisotropic pressure along the two principal directions within the compact object, we obtain physically relevant quantities such as…

General Relativity and Quantum Cosmology · Physics 2016-07-25 Farook Rahaman , Sunil D. Maharaj , Iftikar Hossain Sardar , Koushik Chakraborty

We systematically study pulsar light curves, taking into account the special relativistic effect, i.e., the Doppler factor due to the fast spin of the neutron stars, together with the time delay, which comes from the difference of the…

High Energy Astrophysical Phenomena · Physics 2018-12-05 Hajime Sotani , Umpei Miyamoto

We construct rapidly rotating neutron star models in scalar-tensor theories with a massive scalar field. The fact that the scalar field has nonzero mass leads to very interesting results since the allowed range of values of the coupling…

General Relativity and Quantum Cosmology · Physics 2016-11-15 Daniela D. Doneva , Stoytcho S. Yazadjiev

Rapid rotation enhances the dynamo operating in stars, and thus also introducessignificantly stronger magnetic activity than is seen in slower rotators. Many young cool stars still have the rapid, primordial rotation rates induced by the…

Solar and Stellar Astrophysics · Physics 2015-06-03 H. Korhonen

We study neutron star configurations in a simple shift-symmetric subfamily of degenerate higher-order scalar-tensor (DHOST) theories, whose deviations from General Relativity (GR) are characterized by a single parameter. We compute the…

General Relativity and Quantum Cosmology · Physics 2022-11-09 Hamza Boumaza , David Langlois

Current study highlights the physical characteristics of charged anisotropic compact stars by exploring some exact solutions of modified field equations in $f(R,G)$ gravity. A comprehensive analysis is performed from the obtained solutions…

General Relativity and Quantum Cosmology · Physics 2018-06-13 M. Farasat Shamir , Saeeda Zia

A new spectral code for constructing general-relativistic models of rapidly rotating stars with an unprecedented accuracy is presented. As a first application, we reexamine uniformly rotating homogeneous stars and compare our results with…

Astrophysics · Physics 2010-12-23 M. Ansorg , A. Kleinwächter , R. Meinel

We present the field equations governing the equilibrium of rapidly rotating neutron stars in scalar-tensor theories of gravity, as well as representative numerical solutions. The conditions for the presence of a nontrivial scalar field and…

General Relativity and Quantum Cosmology · Physics 2014-02-25 Daniela D. Doneva , Stoytcho S. Yazadjiev , Nikolaos Stergioulas , Kostas D. Kokkotas

We reconsider the problem of a slowly rotating homogeneous star, or Schwarzschild star, when its compactness goes beyond the Buchdahl bound and approaches the gravastar limit $R\to 2M$. We compute surface and integral properties of such…

General Relativity and Quantum Cosmology · Physics 2024-01-23 Philip Beltracchi , Camilo Posada

In this paper, we study the stellar structure in terms of alternative theory of gravity specially by f (R;T) gravity theory. Here, we consider the function f (R;T) = R+2VT where R is the Ricci scalar, T is the stress-energy momentum and V…

General Relativity and Quantum Cosmology · Physics 2021-06-24 J. Kumar , H. D. Singh , A. K. Prasad

Massive stars exhibit a variety of instabilities, many of which are poorly understood. We explore instabilities induced by centrifugal forces and angular momentum transport in massive rotating stars. First, we derive and numerically solve…

Solar and Stellar Astrophysics · Physics 2022-04-08 Yanlong Shi , Jim Fuller

In modeling a relativistic disk around a compact object, the self-gravity of the disk is often neglected while it needs to be incorporated for more accurate descriptions in several circumstances. Extending the Komatsu-Eriguchi-Hachisu…

High Energy Astrophysical Phenomena · Physics 2024-10-29 Yoonsoo Kim , Jinho Kim , Hee Il Kim , Hyung Mok Lee

We identify combinations of observables for rotating neutron stars that can one day bear on the question of whether there can be first order phase transitions in the neutron matter therein. We employ the Hartle-Thorne theory for stationary,…

Nuclear Theory · Physics 2023-11-08 Pablo Navarro Moreno , Felipe J. Llanes-Estrada , Eva Lope-Oter

We consider both mode calculations and time evolutions of axial r-modes for relativistic uniformly rotating non-barotropic neutron stars, using the slow-rotation formalism, in which rotational corrections are considered up to linear order…

General Relativity and Quantum Cosmology · Physics 2014-11-17 Johannes Ruoff , Kostas D. Kokkotas

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 construct sequences of rapidly rotating neutron stars in dilatonic Einstein-Gauss-Bonnet theory, employing two equations of state for the nuclear matter. We analyze the dependence of the physical properties of these neutron stars on the…

General Relativity and Quantum Cosmology · Physics 2016-06-22 Burkhard Kleihaus , Jutta Kunz , Sindy Mojica , Marco Zagermann

In this work, we study the gravitational back-reaction (i.e., the "self-force") of a point mass moving around a non-rotating, compact star on a circular orbit. We find that the additional self-force, comparing with the case with a point…

General Relativity and Quantum Cosmology · Physics 2024-06-05 Xuefeng Feng , Huan Yang