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The magnetar magnetosphere is gradually twisted by shearing from footpoint motion, and stored magnetic energy also increases at the same time. When a state exceeds a threshold, flares/outbursts manifest themselves as a result of a…

High Energy Astrophysical Phenomena · Physics 2018-04-25 Yasufumi Kojima

Spherical harmonics (SH) have been extensively used as a basis for analyzing the morphology of particles in granular mechanics. The use of SH is facilitated by mapping the particle coordinates onto a unit sphere, in practice often a…

Soft Condensed Matter · Physics 2024-11-14 Mahmoud Shaqfa , Wim M. van Rees

We study the emission of gravitational waves from spheroidal magnetized strange stars for both an isolated slowly rotating star and a binary system. In the first case, we compute the quadrupole moment and the amplitude of gravitational…

General Relativity and Quantum Cosmology · Physics 2024-02-01 S. López Pérez , D. Manreza Paret , A. Pérez Martínez

We consider a modified gravity theory, $f(R)=R+\alpha R^n-\frac{\mu^4}{R^m}$, in the metric formulation and analyze the contribution of electromagnetic field on the range of dynamical instability of a star filled with anisotropic matter.…

General Physics · Physics 2015-10-22 H. Rizwana Kausar , Ifra Noureen , M. Umair Shahzad

We calculate axisymmetric spheroidal modes of neutron stars magnetized with an axisymmetric poloidal magnetic field. We use polytropes of the indices $n\sim1$ as background equilibrium models of neutron stars where we ignore the deformation…

High Energy Astrophysical Phenomena · Physics 2017-12-06 Umin Lee

The magnetic geometry of the surface magnetic fields of more than 55 cool stars have now been mapped using spectropolarimetry. In order to better understand these observations, we compare the magnetic field topology at different surface…

Solar and Stellar Astrophysics · Physics 2017-01-25 L. T. Lehmann , M. M. Jardine , A. A. Vidotto , D. H. Mackay , V. See , J. -F. Donati , C. P. Folsom , S. V. Jeffers , S. C. Marsden , J. Morin , P. Petit

From a set of stellar spectropolarimetric observations, we report the detection of surface magnetic fields in a sample of four solar-type stars, namely HD 73350, HD 76151, HD 146233 (18 Sco) and HD 190771. Assuming that the observed…

A model of magnetic field structure is presented to help test the prevalence of flux freezing in star-forming clouds of various shapes, orientations, and degrees of central concentration, and to estimate their magnetic field strength. The…

Astrophysics of Galaxies · Physics 2018-11-28 Philip C. Myers , Shantanu Basu , Sayantan Auddy

We calculate non-axisymmetric oscillations of neutron stars magnetized by purely poloidal magnetic fields. We use polytropes of index $n=1$ and 1.5 as a background model, where we ignore the equilibrium deformation due to the magnetic…

High Energy Astrophysical Phenomena · Physics 2015-12-16 Hidetaka Asai , Umin Lee , Shijun Yoshida

Stellar spin is one of the fundamental quantities that characterize a star itself and its planetary system. Nevertheless, stellar spin-down mechanisms in protostellar and pre-main-sequence stellar phases have been a long-standing problem in…

Solar and Stellar Astrophysics · Physics 2024-12-20 Shinsuke Takasao , Masanobu Kunitomo , Takeru K. Suzuki , Kazunari Iwasaki , Kengo Tomida

An oblique pulsar magnetosphere with a plasma conductivity is studied by using a pseudo-spectral method. In the pseudo-spectral method, the time-dependent Maxwell equations are solved, both electric and magnetic fields are expanded in terms…

High Energy Astrophysical Phenomena · Physics 2016-07-27 Gang Cao , Li Zhang , Sineng Sun

A highly accurate, multi-domain spectral code is used in order to construct sequences of general relativistic, differentially rotating neutron stars in axisymmetry and stationarity. For bodies with a spheroidal topology and a homogeneous or…

General Relativity and Quantum Cosmology · Physics 2016-06-01 Marcus Ansorg , Dorota Gondek-Rosińska , Loïc Villain

We consider the gravitational potential of a rotating star with non-uniform density to derive the orbital and epicyclic frequencies of the particles orbiting the star. We assume that the star is composed of concentric spheroids of constant…

Solar and Stellar Astrophysics · Physics 2022-08-17 D. A. Bollimpalli

A deformation of a neutron star due to its own magnetic field is an important issue in gravitational wave astronomy, since a misaligned rotator with small ellipticity may emit continuous gravitational wave that may be observed by…

High Energy Astrophysical Phenomena · Physics 2015-06-16 Shin'ichirou Yoshida

Magnetar magnetospheres are strongly twisted, and are able to power sudden energetic events through the rapid release of stored electromagnetic energy. In this paper, we investigate twisted relativistic force-free axisymmetric…

High Energy Astrophysical Phenomena · Physics 2023-11-15 D. Ntotsikas , K. N. Gourgouliatos , I. Contopoulos , S. K. Lander

The stationary axisymmetric force-free magnetosphere of a pulsar is considered. We present an exact dipolar solution of the pulsar equation, construct the magnetospheric model on its basis and examine its observational support. The new…

High Energy Astrophysical Phenomena · Physics 2016-08-30 S. A. Petrova

Magnetar magnetospheres gradually become twisted due to shearing by footpoint motion. The axisymmetric solutions for the force-free field with a power-law current model are calculated by taking into account general relativistic effects.…

High Energy Astrophysical Phenomena · Physics 2017-04-19 Yasufumi Kojima

Electrospheres are environments with the same origin as pulsars; a highly magnetized rotating neutron star. In pulsars, a cascade of electron-positron pair creation enriches the plasma. The plasma surrounding an electrosphere consists only…

High Energy Astrophysical Phenomena · Physics 2024-02-28 Fabrice Mottez

We determine constraints on the form of axisymmetric toroidal magnetic fields dictated by hydrostatic balance in a type II superconducting neutron star with a barotropic equation of state. Using Lagrangian perturbation theory, we find the…

Astrophysics · Physics 2009-11-16 Taner Akgun , Ira Wasserman

The equilibrium configurations of slowly rotating anisotropic self-gravitating fluids are computed using the extended Hartle structure equations, including anisotropic effects, derived in our previous paper. We focus on the so-called…

General Relativity and Quantum Cosmology · Physics 2025-10-20 Philip Beltracchi , Camilo Posada
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