scholarly journals Equatorial Geodesics Around the Magnetars

2017 ◽  
Vol 45 ◽  
pp. 1760050
Author(s):  
Viviane A. P. Alfradique ◽  
Orlenys N. Troconis ◽  
Rodrigo P. Negreiros
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
Complete Solution ◽  
Compact Object ◽  
Relativistic Effects ◽  
Schwarzschild Solution ◽  
Soft Gamma Repeaters ◽  
Definition Of ◽  
The Magnetic Field

Neutron stars manifest themselves as different classes of astrophysical sources that are associated to distinct phenomenology. Here we focus our attention on magnetars (or strongly magnetized neutron stars) that are associated to Soft Gamma Repeaters and Anomalous X-ray Pulsars. The magnetic field on surface of these objects, reaches values greater than [Formula: see text] G. Under intense magnetic fields, relativistic effects begin to be decisive for the definition of the structure and evolution of these objects. We are tempted to question ourselves to how strengths fields affect the structure of neutron star. In this work, our objective is study and compare two solutions of Einstein-Maxwell equations: the Bonnor solution, which is an analytical solution that describe the exterior spacetime for a massive compact object which has a magnetic field that is characterize as a dipole field and a complete solution that describe the interior and exterior spacetime for the same source found by numerical methods). For this, we describe the geodesic equations generated by such solutions. Our results show that the orbits generated by the Bonnor solution are the same as described by numerical solution. Also, show that the inclusion of magnetic fields with values up to [Formula: see text]G in the center of the star does not modify sharply the particle orbits described around this star, so the use of Schwarzschild solution for the description of these orbits is a reasonable approximation.

scholarly journals Spin-1/2 Particles under the Influence of a Uniform Magnetic Field in the Interior Schwarzschild Solution

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 467
Author(s):  
Fayçal Hammad ◽  
Alexandre Landry ◽  
Parvaneh Sadeghi
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Total Mass ◽  
Uniform Magnetic Field ◽  
Energy Levels ◽  
Relativistic Wave Equation ◽  
Relativistic Wave ◽  
Schwarzschild Solution ◽  
Relativistic Regime ◽  
The Magnetic Field

The relativistic wave equation for spin-1/2 particles in the interior Schwarzschild solution in the presence of a uniform magnetic field is obtained. The fully relativistic regime is considered, and the energy levels occupied by the particles are derived as functions of the magnetic field, the radius of the massive sphere and the total mass of the latter. As no assumption is made on the relative strengths of the particles’ interaction with the gravitational and magnetic fields, the relevance of our results to the physics of the interior of neutron stars, where both the gravitational and the magnetic fields are very intense, is discussed.

scholarly journals Cyclotron lines in highly magnetized neutron stars

2019 ◽  
Vol 622 ◽  
pp. A61 ◽  
Author(s):  
R. Staubert ◽  
J. Trümper ◽  
E. Kendziorra ◽  
D. Klochkov ◽  
K. Postnov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
Direct Measurement ◽  
Resonant Scattering ◽  
Electron Cyclotron ◽  
X Ray ◽  
Cyclotron Line ◽  
The Magnetic Field ◽  
Proton Cyclotron

Cyclotron lines, also called cyclotron resonant scattering features are spectral features, generally appearing in absorption, in the X-ray spectra of objects containing highly magnetized neutron stars, allowing the direct measurement of the magnetic field strength in these objects. Cyclotron features are thought to be due to resonant scattering of photons by electrons in the strong magnetic fields. The main content of this contribution focusses on electron cyclotron lines as found in accreting X-ray binary pulsars (XRBP) with magnetic fields on the order of several 1012Gauss. Also, possible proton cyclotron lines from single neutron stars with even stronger magnetic fields are briefly discussed. With regard to electron cyclotron lines, we present an updated list of XRBPs that show evidence of such absorption lines. The first such line was discovered in a 1976 balloon observation of the accreting binary pulsar Hercules X-1, it is considered to be the first direct measurement of the magnetic field of a neutron star. As of today (end 2018), we list 35 XRBPs showing evidence of one ore more electron cyclotron absorption line(s). A few have been measured only once and must be confirmed (several more objects are listed as candidates). In addition to the Tables of objects, we summarize the evidence of variability of the cyclotron line as a function of various parameters (especially pulse phase, luminosity and time), and add a discussion of the different observed phenomena and associated attempts of theoretical modeling. We also discuss our understanding of the underlying physics of accretion onto highly magnetized neutron stars. For proton cyclotron lines, we present tables with seven neutron stars and discuss their nature and the physics in these objects.

scholarly journals Topology of Coronal Magnetic Fields: Extending the Magnetic Skeleton Using Null-like Points

Solar Physics ◽  
2020 ◽  
Vol 295 (12) ◽  
Author(s):  
Daniel T. Lee ◽  
Daniel S. Brown
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Free Field ◽  
Point Sources ◽  
Topological Features ◽  
Perpendicular Component ◽  
Definition Of ◽  
Magnetic Null ◽  
The Magnetic Field ◽  
Continuous Source

AbstractMany phenomena in the Sun’s atmosphere are magnetic in nature and study of the atmospheric magnetic field plays an important part in understanding these phenomena. Tools to study solar magnetic fields include magnetic topology and features such as magnetic null points, separatrix surfaces, and separators. The theory of these has most robustly been developed under magnetic charge topology, where the sources of the magnetic field are taken to be discrete, but observed magnetic fields are continuously distributed, and reconstructions and numerical simulations typically use continuously distributed magnetic boundary conditions. This article investigates the pitfalls in using continuous-source descriptions, particularly when null points on the $z=0$ z = 0 plane are obscured by the continuous flux distribution through, e.g., the overlap of non-point sources. The idea of null-like points on the boundary is introduced where the parallel requirement on the field $B_{\parallel }=0$ B ∥ = 0 is retained but the requirement on the perpendicular component is relaxed, i.e. $B_{\perp }\ne 0$ B ⊥ ≠ 0 . These allow the definition of separatrix-like surfaces which are shown (through use of a squashing factor) to be a class of quasi-separatrix layer, and separator-like lines which retain the x-line structure of separators. Examples are given that demonstrate that the use of null-like points can reinstate topological features that are eliminated in the transition from discrete to continuous sources, and that their inclusion in more involved cases can enhance understanding of the magnetic structure and even change the resulting conclusions. While the examples in this article use the potential approximation, the definition of null-like points is more general and may be employed in other cases such as force-free field extrapolations and MHD simulations.

scholarly journals Magnetic Field Evolution in Neutron Star Crusts: Beyond the Hall Effect

Symmetry ◽  
2022 ◽  
Vol 14 (1) ◽  
pp. 130
Author(s):  
Konstantinos N. Gourgouliatos ◽  
Davide De Grandis ◽  
Andrei Igoshev
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
Hall Effect ◽  
Thermal Emission ◽  
Ohmic Dissipation ◽  
Field Evolution ◽  
The Universe ◽  
The Magnetic Field ◽  
Maxwell Stresses

Neutron stars host the strongest magnetic fields that we know of in the Universe. Their magnetic fields are the main means of generating their radiation, either magnetospheric or through the crust. Moreover, the evolution of the magnetic field has been intimately related to explosive events of magnetars, which host strong magnetic fields, and their persistent thermal emission. The evolution of the magnetic field in the crusts of neutron stars has been described within the framework of the Hall effect and Ohmic dissipation. Yet, this description is limited by the fact that the Maxwell stresses exerted on the crusts of strongly magnetised neutron stars may lead to failure and temperature variations. In the former case, a failed crust does not completely fulfil the necessary conditions for the Hall effect. In the latter, the variations of temperature are strongly related to the magnetic field evolution. Finally, sharp gradients of the star’s temperature may activate battery terms and alter the magnetic field structure, especially in weakly magnetised neutron stars. In this review, we discuss the recent progress made on these effects. We argue that these phenomena are likely to provide novel insight into our understanding of neutron stars and their observable properties.

Production of monopole–antimonopole pairs in very intense but slowly varying magnetic field

2020 ◽  
Vol 35 (21) ◽  
pp. 2050116
Author(s):  
Giorgio Calucci
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
Time Variation ◽  
The Magnetic Field ◽  
Astrophysical Phenomena

The production of pairs of monopole–antimonopole in presence of extremely intense magnetic fields, is briefly investigated in the case where the magnetic field undergoes also a time variation. The possibility that similar conditions are realized, with a production of ordinary particles, was already considered for astrophysical phenomena, e.g. some phases of evolution of neutron stars.

scholarly journals Magnetic Field Decay, or Just Period-Dependent Beaming?

2004 ◽  
Vol 218 ◽  
pp. 41-44 ◽  
Author(s):  
Joeri van Leeuwen ◽  
Frank Verbunt
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Velocity Distribution ◽  
Neutron Stars ◽  
Time Scale ◽  
Radio Pulsar ◽  
New Born ◽  
Field Decay ◽  
The Magnetic Field

Several recent papers conclude that radio-pulsar magnetic fields decay on a time-scale of 10 Myr, apparently contradicting earlier results. We have implemented the methods of these papers in our code and show that this preference for rapid field decay is caused by the assumption that the beaming fraction does not depend on the period. When we do include this dependence, we find that the observed pulsar properties are reproduced best when the modeled field does not decay. When we assume that magnetic fields of new-born neutron stars are from a distribution sufficiently wide to explain magnetars, the magnetic field and period distributions we predict for radio are pulsars wider than observed. Finally we find that the observed velocities overestimate the intrinsic velocity distribution.

scholarly journals EFFECT OF STRONG MAGNETIC FIELDS ON THE EQUILIBRIUM OF A DEGENERATE GAS OF NUCLEONS AND ELECTRONS

1996 ◽  
Vol 10 (23) ◽  
pp. 1141-1149 ◽  
Author(s):  
CHOON-LIN HO ◽  
V.R. KHALILOV ◽  
CHI YANG
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
Strong Magnetic Field ◽  
Constant Magnetic Field ◽  
Fermi Momentum ◽  
Magnetic Field Induction ◽  
Strong Magnetic Fields ◽  
Field Induction ◽  
The Magnetic Field

We obtain the equations that define the equilibrium of a homogeneous relativistic gas of neutrons, protons and electrons in a constant magnetic field as applied to the conditions that probably occur near the center of neutron stars. We compute the relative densities of the particles at equilibrium and the Fermi momentum of electrons in the strong magnetic field as function of the density of neutrons and the magnetic field induction. Novel features are revealed as to the ratio of the number of protons to the number of neutrons at equilibrium in the presence of large magnetic fields.

THE SPIN-UP OF ACCRETING NEUTRON STARS IN BINARY SYSTEMS

2011 ◽  
Vol 20 (10) ◽  
pp. 2019-2022
Author(s):  
J. WANG ◽  
C. M. ZHANG ◽  
Y. H. ZHAO
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
Binary Systems ◽  
Initial Conditions ◽  
Initial Period ◽  
Spin Period ◽  
The Magnetic Field ◽  
Initial Magnetic Field

In binary systems, the rotation of neutron stars can be spun up by the accreted material, and at the same time the decay of their magnetic fields occur in the accretion phase. As a result, the spin period may arrive at a minimum of about 1.5 ms, corresponding to a bottom value of the magnetic field ~ 108 G. Taking the conditions: (i) initial magnetic field varying from 1011 G to 1013 G while setting period as 100 s, (ii) initial period as 1–100 s at B = 5 × 1012 G , we find that this minimum of spin period seems independent of these initial conditions.

scholarly journals MAGNETIC FIELDS IN ACCRETION DISCS AROUND NEUTRON STARS — CONSEQUENCES FOR THE CHANGE OF SPIN

2013 ◽  
Vol 23 ◽  
pp. 106-110
Author(s):  
LUCA NASO ◽  
JOHN MILLER ◽  
WLODEK KLUŹNIAK
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
Accretion Disk ◽  
Accretion Disks ◽  
Magnetic Field Profile ◽  
History Of ◽  
The One ◽  
The Universe ◽  
The Magnetic Field

Accretion disks are ubiquitous in the universe and it is generally accepted that magnetic fields play a pivotal role in accretion-disk physics. The spin history of millisecond pulsars, which are usually classified as magnetized neutron stars spun up by an accretion disk, depends sensitively on the magnetic field structure, and yet highly idealized models from the 80s are still being used for calculating the magnetic field components. We present a possible way of improving the currently used models with a semi-analytic approach. The resulting magnetic field profile of both the poloidal and the toroidal component can be very different from the one suggested previously. This might dramatically change our picture of which parts of the disk tend to spin the star up or down.

scholarly journals The Physics of Soft Gamma Repeaters

2000 ◽  
Vol 195 ◽  
pp. 245-254
Author(s):  
C. Thompson
Keyword(s):  
Magnetic Field ◽  
Free Energy ◽  
Neutron Star ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
Strong Magnetic Fields ◽  
Dominant Source ◽  
Soft Gamma Repeaters ◽  
Physical Diagnostics ◽  
Fireball Model

I describe the evidence that Soft Gamma Repeaters are magnetars—neutron stars in which a decaying magnetic field (rather than rotation) is the dominant source of free energy. The focus here is on the bursting emission of these sources and on direct physical diagnostics of very strong magnetic fields (B ≳ 10 BQED = 4.4 × 1014 G). I also summarize the trapped fireball model of SGR outbursts, the influence of QED processes on their spectra and lightcurves, and the genetic connection between neutron star magnetism and the violent fluid motions in a collapsing supernova core.

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