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The origins of the various outbursts of hard X-rays from magnetars (highly magnetized neutron stars) are still unknown. We identify instabilities in relativistic magnetospheres that can explain a range of X-ray flare luminosities. Crustal…

High Energy Astrophysical Phenomena · Physics 2023-04-27 J. F. Mahlmann , A. A. Philippov , V. Mewes , B. Ripperda , E. R. Most , L. Sironi

It is generally assumed that the magnetic fields of millisecond pulsars (MSPs) are $\sim 10^{8}$G. We argue that this may not be true and the fields may be appreciably greater. We present six evidences for this: (1) The $\sim 10^{8}$ G…

Solar and Stellar Astrophysics · Physics 2010-08-02 Rafael S. de Souza , Reuven Opher

Motivated by the problem of the formation of active regions from a deep-seated solar magnetic field, we consider the nonlinear three-dimensional evolution of magnetic buoyancy instabilities resulting from a smoothly stratified horizontal…

Astrophysics · Physics 2009-11-13 Evy Kersale , David W. Hughes , Steven M. Tobias

The r-mode instability in rotating relativistic stars has been shown recently to have important astrophysical implications (including the emission of detectable gravitational radiation, the explanation of the initial spins of young neutron…

General Relativity and Quantum Cosmology · Physics 2014-11-17 Nikolaos Stergioulas , Jose A. Font

This paper provides a brief overview of the formation of stellar fossil magnetic fields and what potential instabilities may occur given certain configurations of the magnetic field. In particular, a purely magnetic instability can occur…

Solar and Stellar Astrophysics · Physics 2016-10-28 Kyle Augustson , Stephane Mathis , Antoine Strugarek

Dynamical instabilities in protoneutron stars may produce gravitational waves whose observation could shed light on the physics of core-collapse supernovae. When born with sufficient differential rotation, these stars are susceptible to a…

The Rossi X-ray Timing Explorer has detected nearly coherent oscillations in the tails of type I X-ray bursts from 17 low-mass X-ray binaries. The oscillations are thought to be generated by brightness fluctuations associated with a surface…

Astrophysics · Physics 2011-02-11 Ramesh Narayan , Randall L. Cooper

Magnetic fields have been observed in massive Ap/Bp stars and presumably are also present in the radiative zone of solar-like stars. Yet, to date there is no clear understanding of the dynamics of the magnetic field in stably stratified…

Solar and Stellar Astrophysics · Physics 2023-03-27 G. Monteiro , G. Guerrero , F. Del Sordo , A. Bonanno , P. K. Smolarkiewicz

Neutron stars contain persistent, ordered magnetic fields that are the strongest known in the Universe. However, their magnetic fluxes are similar to those in magnetic A and B stars and white dwarfs, suggesting that flux conservation during…

Astrophysics · Physics 2009-11-13 Andreas Reisenegger

We study here the r-modes in the Cowling approximation of a slowly rotating and magnetized neutron star with a poloidal magnetic field, where we neglect any deformations of the spherical symmetry of the star. We were able to quantify the…

General Relativity and Quantum Cosmology · Physics 2013-11-27 Cecilia Chirenti , Jozef Skakala

We show that young pulsars with normal magnetic fields, which are born as fast rotating neutron stars (NSs) in Type II/Ib supernova explosions, can slow down quickly by relativistic particles emission along their magnetic axis. When they…

Astrophysics · Physics 2007-05-23 Arnon Dar

We examine the spin-up of low luminosity, low mass X-ray binaries (LMXBs) to millisecond pulsars (MSPs). In the conventional spin-up model of the Ghosh & Lamb type, where the stellar magnetic field interacts with the Keplerian accretion…

Astrophysics · Physics 2009-10-30 Insu Yi , Jonathan E. Grindlay

A brief review of the stability of rotating relativistic stars is followed by a more detailed discussion of recent work on an instability of r-modes, modes of rotating stars that have axial parity in the slow-rotation limit. These modes may…

General Relativity and Quantum Cosmology · Physics 2008-11-26 John L. Friedman , Keith H. Lockitch

According to the recycling scenario, millisecond pulsars (MSPs) have evolved from low-mass X-ray binaries (LMXBs). Their orbits are expected to be circular due to tidal interactions during the binary evolution, as observed in most of the…

High Energy Astrophysical Phenomena · Physics 2015-05-19 Long Jiang , Xiang-Dong Li , Jishnu Dey , Mira Dey

Magnetohydrodynamic (MHD) instabilities can play an important role in the dynamics of the pulsar magnetosphere and can be responsible for the formation of various structures. We consider the instability caused by a gradient of the magnetic…

Solar and Stellar Astrophysics · Physics 2014-03-05 Vadim Urpin

The origin of a part of the single pulsars with relatively low magnetic fields B < 1E12 G and with characteristic times Tau < 1E7 yr is established. Such pulsars occur as a result of the disruption of High Mass X-ray Binary Systems after a…

Astrophysics · Physics 2009-11-10 O. H. Guseinov , A. O. Allakhverdiev , S. Tagieva , O. Taskin

Strong magnetic fields in relativistic stars can be a cause of crust fracturing, resulting in the excitation of global torsional oscillations. Such oscillations could become observable in gravitational waves or in high-energy radiation,…

Astrophysics · Physics 2009-11-06 Neophytos Messios , Demetrios B. Papadopoulos , Nikolaos Stergioulas

The extraordinary energetic activity of magnetars is usually explained in terms of dissipation of a huge internal magnetic field of the order of $10^{15-16}$G. How such a strong magnetic field can originate during the formation of a neutron…

High Energy Astrophysical Phenomena · Physics 2017-07-26 A. G. Pili , N. Bucciantini , L. Del Zanna

Observations of surface magnetic fields of cool stars reveal a large diversity of configurations. Although there is now a consensus that these fields are generated through dynamo processes occurring within the convective zone, the physical…

Solar and Stellar Astrophysics · Physics 2022-10-05 B. Zaire , L. Jouve , T. Gastine , J-F. Donati , J. Morin , N. Landin , C. P. Folsom

We discuss some aspects of Pereira et al. (2018) concerning magnetars described by nonlinear theories of the electromagnetism and make the case for the Born-Infeld Lagrangian. We focus on the increase of toroidal magnetic fields in these…

High Energy Astrophysical Phenomena · Physics 2019-04-12 Jonas P. Pereira , Jaziel G. Coelho , Rafael C. R. de Lima