Strongly Magnetized Sources: QED and X-ray Polarization

Radiative corrections of quantum electrodynamics cause a vacuum threaded by a magnetic field to be birefringent. This means that radiation of different polarizations travels at different speeds. Even in the strong magnetic fields of astrophysical sources, the difference in speed is small. However, it has profound consequences for the extent of polarization expected from strongly magnetized sources. We demonstrate how the birefringence arises from first principles, show how birefringence affects the polarization state of radiation and present recent calculations for the expected polarization from magnetars and X-ray pulsars.

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SIMILARITIES OF SGRs WITH LOW MAGNETIC FIELD AND WHITE DWARF PULSARS

International Journal of Modern Physics Conference Series ◽

10.1142/s2010194512008276 ◽

2012 ◽

Vol 18 ◽

pp. 96-100 ◽

Cited By ~ 3

Author(s):

J. G. COELHO ◽

M. MALHEIRO

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

White Dwarf ◽

Alternative Explanation ◽

Gamma Ray ◽

Strong Magnetic Fields ◽

X Ray ◽

Surface Magnetic Field ◽

Astrophysical Objects ◽

Low Magnetic Field

Some of the most interesting types of astrophysical objects that have been intensively studied in the recent years are the Anomalous X-ray Pulsars (AXPs) and Soft Gamma-ray Repeaters (SGRs) seen usually as neutron stars pulsars with super strong magnetic fields. However, in the last two years two SGRs with low magnetic fields have been detected. Moreover, fast and very magnetic white dwarf pulsars have also been observed in the last years. Based on these new pulsar discoveries, white dwarf pulsars have been proposed as an alternative explanation to the observational features of SGRs and AXPs. Here we present several properties of these SGRs/AXPs as WD pulsar, in particular the surface magnetic field and the magnetic dipole momentum.

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Magnetars

International Astronomical Union Colloquium ◽

10.1017/s0252921100060966 ◽

2000 ◽

Vol 177 ◽

pp. 669-680

Author(s):

Christopher Thompson

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Neutron Stars ◽

Particle Emission ◽

Strong Magnetic Fields ◽

X Ray ◽

Soft Gamma Repeaters

AbstractI summarize recent observational and theoretical advances in the understanding of the Soft Gamma Repeaters and the Anomalous X-ray Pulsars. Several direct physical arguments point to very strong magnetic fields (B> 10BQED= 4.4 × 1014 G) in SGR outbursts. The connection between these two classes of neutron stars is examined. Their persistent X-ray emission and spindown behavior are interpreted in the magnetar model, where a decaying magnetic field dominates all other sources of energy for radiative and particle emission. The response of a magnetic field to the violent motions in a supernova core is also examined, with a focus on mechanisms that may impart unusually large kicks.

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Effect of Vacuum Polarization in a Strong Magnetic Field and Spectral Features of X-Ray Source Emission

International Astronomical Union Colloquium ◽

10.1017/s0252921100012161 ◽

1990 ◽

Vol 115 ◽

pp. 78-84

Author(s):

Yu. N. Gnedin

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Neutron Stars ◽

Electromagnetic Radiation ◽

Vacuum Polarization ◽

Spectral Features ◽

Strong Magnetic Fields ◽

X Ray ◽

Electron Positron ◽

Medium Vacuum

AbstractIn strong magnetic fields of neutron stars electron-positron vacuum behaves as an anisotropic medium. Vacuum influences the generation and propagation of electromagnetic radiation in plasma and changes the spectrum of radiation. As a result the change of cyclotron lines shape and appearance of specific “vacuum lines” should be observed in X-ray spectra of accreting neutron stars.

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Effect of Magnetic Fields on the Resistance and Microstructure of Al-Cu Alloy during Solidification Processing

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.287-290.2916 ◽

2011 ◽

Vol 287-290 ◽

pp. 2916-2920

Author(s):

Chun Yan Ban ◽

Peng Qian ◽

Xu Zhang ◽

Qi Xian Ba ◽

Jian Zhong Cui

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Turning Points ◽

Probe Method ◽

Solidification Processing ◽

Ac Magnetic Field ◽

Dc Magnetic Field ◽

Cu Alloy ◽

The Difference ◽

Good Agreement

The resistance of Al-21%Cu alloy under no magnetic field, DC magnetic field and AC magnetic field from liquid to solid was measured by a four-probe method. The difference of resistance versus temperature curves (R-T curves) was analyzed. It is found that the R-T curves of Al-21%Cu alloy are monotone decreasing and have two obvious turning points. Under DC magnetic field, the liquidus and solidus temperatures of the alloy both decrease, while under AC magnetic field, the liquidus and solidus temperatures both increase. There is a good agreement between the microstructure of quenching sample and R-T curves. The mechanism of the effect of magnetic fields was discussed.

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The measurement of the energy of cosmic rays - II—The curvature measurements and the energy spectrum

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1936.0070 ◽

1936 ◽

Vol 154 (883) ◽

pp. 573-587 ◽

Cited By ~ 27

Keyword(s):

Magnetic Field ◽

Energy Spectrum ◽

Cosmic Rays ◽

Magnetic Fields ◽

Strong Magnetic Fields ◽

The Earth ◽

Primary Particles ◽

Curvature Measurements

Both the penetrating power of the cosmic rays through material absorbers and their ability to reach the earth in spite of its magnetic field, make it certain that the energy of many of the primary particles must reach at least 10 11 e-volts. However, the energy measurements by Kunze, and by Anderson, using cloud chambers in strong magnetic fields, have extended only to about 5 x 10 9 e-volts. Particles of greater energy were reported, but the curvature of their tracks was too small to be measured with certainty. We have extended these energy measurements to somewhat higher energies, using a large electro-magnet specially built for the purpose and described in Part I. As used in these experiments, the magnet allowed the photography of tracks 17 cm long in a field of about 14,000 gauss. The magnet weighed about 11,000 kilos and used a power of 25 kilowatts.

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Modeling of magneto-conductivity of bismuth selenide: a topological insulator

SN Applied Sciences ◽

10.1007/s42452-021-04397-8 ◽

2021 ◽

Vol 3 (4) ◽

Author(s):

Yogesh Kumar ◽

Rabia Sultana ◽

Prince Sharma ◽

V. P. S. Awana

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Single Crystal ◽

Single Crystals ◽

X Ray Diffraction ◽

Field Range ◽

X Ray ◽

Bulk Carriers ◽

Different Temperatures

AbstractWe report the magneto-conductivity analysis of Bi2Se3 single crystal at different temperatures in a magnetic field range of ± 14 T. The single crystals are grown by the self-flux method and characterized through X-ray diffraction, Scanning Electron Microscopy, and Raman Spectroscopy. The single crystals show magnetoresistance (MR%) of around 380% at a magnetic field of 14 T and a temperature of 5 K. The Hikami–Larkin–Nagaoka (HLN) equation has been used to fit the magneto-conductivity (MC) data. However, the HLN fitted curve deviates at higher magnetic fields above 1 T, suggesting that the role of surface-driven conductivity suppresses with an increasing magnetic field. This article proposes a speculative model comprising of surface-driven HLN and added quantum diffusive and bulk carriers-driven classical terms. The model successfully explains the MC of the Bi2Se3 single crystal at various temperatures (5–200 K) and applied magnetic fields (up to 14 T).

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Investigating the Magnetospheres of Rapidly Rotating B-type Stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317002812 ◽

2016 ◽

Vol 12 (S329) ◽

pp. 369-372

Author(s):

C. L. Fletcher ◽

V. Petit ◽

Y. Nazé ◽

G. A. Wade ◽

R. H. Townsend ◽

...

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Centrifugal Force ◽

Point Of View ◽

Closed Field ◽

Theoretical Point ◽

X Rays ◽

Rapid Rotation ◽

X Ray ◽

Surface Magnetic Field

AbstractRecent spectropolarimetric surveys of bright, hot stars have found that ~10% of OB-type stars contain strong (mostly dipolar) surface magnetic fields (~kG). The prominent paradigm describing the interaction between the stellar winds and the surface magnetic field is the magnetically confined wind shock (MCWS) model. In this model, the stellar wind plasma is forced to move along the closed field loops of the magnetic field, colliding at the magnetic equator, and creating a shock. As the shocked material cools radiatively it will emit X-rays. Therefore, X-ray spectroscopy is a key tool in detecting and characterizing the hot wind material confined by the magnetic fields of these stars. Some B-type stars are found to have very short rotational periods. The effects of the rapid rotation on the X-ray production within the magnetosphere have yet to be explored in detail. The added centrifugal force due to rapid rotation is predicted to cause faster wind outflows along the field lines, leading to higher shock temperatures and harder X-rays. However, this is not observed in all rapidly rotating magnetic B-type stars. In order to address this from a theoretical point of view, we use the X-ray Analytical Dynamical Magnetosphere (XADM) model, originally developed for slow rotators, with an implementation of new rapid rotational physics. Using X-ray spectroscopy from ESA’s XMM-Newton space telescope, we observed 5 rapidly rotating B-types stars to add to the previous list of observations. Comparing the observed X-ray luminosity and hardness ratio to that predicted by the XADM allows us to determine the role the added centrifugal force plays in the magnetospheric X-ray emission of these stars.

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Magneto- and Tensoresistance of the p Ge Compensated Crystals in the Range of Weak, Intermediate and Classically Strong Magnetic Fields

Фізика і хімія твердого тіла ◽

10.15330/pcss.17.1.43-47 ◽

2016 ◽

Vol 17 (1) ◽

pp. 43-47 ◽

Cited By ~ 1

Author(s):

G.P. Gaidar

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Mechanical Stress ◽

Elastic Deformation ◽

Crystallographic Orientation ◽

Longitudinal Axis ◽

Mechanical Stresses ◽

Strong Magnetic Fields ◽

Compensation Factor

On the crystalsof compensatedp‑Ge (with the compensation factor of k = NSb/NGa = 0.5) the transverse (Н ^ (J // X)) magnetoresistance (within the magnetic fields of 0 < Н £ 22.3 kOe) at fixed values of the mechanical stresses Хі = 0; 0.2; 0.4; 0.6; 0.9; 1.1; 1.5 GPa were measured at 77 K. These mechanical stresses X created the elastic deformation along the samples, the crystallographic orientation of which coincided with the direction of [100]. Also at fixed magnetic field intensities Ні = 2; 4; 8; 10; 15; 20; 22.3 kOe the dependencies of resistivity on the mechanical stress X, which coincides with the longitudinal axis of the crystal (X // J // [100]) and changes in the range of 0 £ Х £ 1.5 GPa, were measured. Last dependences characterized by the presence of a minimum in the range of X ~ 0.5 ¸ 0.6 GPa at the minimal magnetic field intensities Н = 2 kOe, which was shifted to the values of X ~ 0.2 ¸ 0.3 GPa with increasing Н up to 22.3 kOe.

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Magneto–rotational and Thermal Evolution of Magnetars with Crustal Magnetic Fields

International Astronomical Union Colloquium ◽

10.1017/s0252921100060978 ◽

2000 ◽

Vol 177 ◽

pp. 681-684 ◽

Cited By ~ 2

Author(s):

U. Geppert ◽

D. Page ◽

M. Colpi ◽

T. Zannias

Keyword(s):

Magnetic Fields ◽

Binary Systems ◽

Thermal Evolution ◽

Cyclotron lines in highly magnetized neutron stars

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834479 ◽

2019 ◽

Vol 622 ◽

pp. A61 ◽

Cited By ~ 34

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.

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