Polarization Study of Gamma-ray Binary Systems

2021 ◽  
Vol 922 (2) ◽  
pp. 260
Author(s):  
Hu Xingxing ◽  
Takata Jumpei
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Binary Systems ◽  
Gamma Ray ◽  
Polarization Degree ◽  
Polarization Angle ◽  
X Ray ◽  
Cone Axis ◽  
Orbital Phase ◽  
The Magnetic Field

Abstract The polarization of X-ray emission is a unique tool used to investigate the magnetic field structure around astrophysical objects. In this paper, we study the linear polarization of X-ray emissions from gamma-ray binary systems based on pulsar scenarios. We discuss synchrotron emission from pulsar wind particles accelerated by a standing shock. We explore three kinds of axisymmetric magnetic field structures: (i) toroidal magnetic fields, (ii) poloidal magnetic fields, and (iii) tangled magnetic fields. Because of the axisymmetric structure, the polarization angle of integrated emission is oriented along or perpendicular to the shock-cone axis projected on the sky and swings around 360° in one orbit. For the toroidal case, the polarization angle is always directed along the shock-cone axis and smoothly changes along the orbital phase. For the poloidal/tangled magnetic field, the direction of the polarization angle depends on the system parameters and orbital phase. In one orbit, the polarization degree for the toroidal case can reach the maximum value of the synchrotron radiation (∼70%), while the maximum polarization degree for poloidal/tangled field cases is several 10%. We apply our model to bright gamma-ray binary LS 5039 and make predictions for future observations. With the expected sensitivity of the Imaging X-ray Polarimetry Explorer, linear polarization can be detected by an observation of several days if the magnetic field is dominated by the toroidal magnetic field. If the magnetic field is dominated by the poloidal/tangled field, significant detection is expected with an observation longer than 10 days.

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.

Performance Evaluation of an MR-Compatible Rotating Anode X-Ray Tube

2013 ◽  
Author(s):  
Mihye Shin ◽  
Prasheel Lillaney ◽  
Waldo Hinshaw ◽  
Rebecca Fahrig
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Magnetic Moments ◽  
X Ray ◽  
Close Proximity ◽  
Motor Design ◽  
Design Requirements ◽  
And Performance ◽  
The Magnetic Field ◽  
Lorentz Force Law

The key technical innovation needed for close proximity hybrid x-ray/MR (XMR) imaging systems is a new rotating anode x-ray tube motor that can operate in the presence of strong magnetic fields. In order for the new motor design to be optimized between conflicting design requirements, we implemented a numerical model for evaluating the dynamics of the motor. The model predicts the amount of produced torque, rotation speed, and time to accelerate based on the Lorentz force law; the motor is accelerated by the interaction between the magnetic moments of the motor wire loops and an external magnetic field. It also includes an empirical model of bearing friction and electromagnetic force from the magnetic field. Our proposed computational model is validated by experiments using several different magnitudes of external magnetic fields, which averagely shows an agreement within 0.5 % error during acceleration. We are using this model to improve the efficiency and performance of future iterations of the x-ray tube motor.

scholarly journals Rheological and Resistance Properties of Magnetorheological Elastomer with Cobalt for Sensor Application

2020 ◽  
Vol 10 (5) ◽  
pp. 1638 ◽  
Author(s):  
Afiq Azri Zainudin ◽  
Nurul Azhani Yunus ◽  
Saiful Amri Mazlan ◽  
Muhammad Kashfi Shabdin ◽  
Siti Aishah Abdul Aziz ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Vibrating Sample Magnetometer ◽  
Magnetorheological Elastomer ◽  
X Ray ◽  
Sensing Applications ◽  
Morphological Aspects ◽  
Frequency Sweep Test ◽  
Applied Forces ◽  
The Magnetic Field

Cobalt particles have been introduced as a filler due to the advantages of embedding their magnetic and electrical properties in magnetorheological elastomer (MRE). In the present research, the rheology and resistance of MRE are experimentally evaluated. Isotropic and anisotropic MRE samples containing silicone rubber and cobalt particles were fabricated. The magnetic properties of MRE are conducted using a vibrating sample magnetometer (VSM). The morphological aspects of MRE are observed by using field emission scanning electron microscopy (FESEM) and characterized by energy-dispersive X-ray spectroscopy (EDX). Rheological properties under various magnetic field strengths were measured for the magnetic field, strain amplitude, and frequency sweep test by using a parallel-plate rheometer. Subsequently, the resistance of MRE is tested under different applied forces and magnetic fields. The MRE storage modulus depicted an enhancement in field-dependent modulus across all the applied magnetic fields. The electrical resistance generated from the sample can be manipulated by external magnetic fields and mechanical loads. The conductivity of MRE is due to the existence of cobalt arrangements observed by FESEM. By introducing cobalt as filler and obtaining satisfactory results, the study might open new avenues for cobalt to be used as filler in MRE fabrication for future sensing applications.

scholarly journals Statistics of Radio-X-Ray Emission and Magnetic Fields in the Intergalactic Medium

1990 ◽  
Vol 139 ◽  
pp. 414-415
Author(s):  
Hitoshi Hanami
Keyword(s):  
Magnetic Field ◽  
Cosmic Rays ◽  
Magnetic Fields ◽  
Intergalactic Medium ◽  
Relativistic Electrons ◽  
X Ray ◽  
Cooling Flows ◽  
Hot Plasma ◽  
Inverse Compton ◽  
The Magnetic Field

X-ray observations have demonstrated that the intergalactic medium in many clusters (cf. Coma, Perseus) contains a thin, hot plasma that may be produced by the accretion process in the gravitational potential of clusters with radiative cooling; this is usually called “cooling flows” (Fabian, Nulsen, and Canizares 1984; Sarazin 1986). On the other hand, the existence of radio halos in some clusters has been reported (Coma: Jaffe, Perola, and Valentijn 1976; A401: Roland et al. 1981). In addition, many elliptical galaxies in the center of clusters are also strong synchrotron radio sources. These radio emissions provide evidence for large amounts of relativistic electrons associated with the active phenomena in or around these galaxies and clusters. We can estimate the values or limits on the magnetic field in the cluster from the limits on the inverse Compton X-ray emission with the synchrotron radio emission (cf. Jaffe 1980). The intracluster field strength Bo is roughly 1 μG. It has been suggested that the influence of cosmic rays and magnetic fields is important for the properties and dynamics of the intercluster medium (Böhringer and Morfill 1988; Soker and Sarazin 1989). If cooling flows are real, this inward flow can impede the escape of the cosmic rays from the central galaxies in clusters and enhance the magnetic field. The confinement of the cosmic rays and the magnetic field in the center of clusters affects the gas of the intracluster medium.

scholarly journals Magnetars and white dwarf pulsars

2016 ◽  
Vol 25 (09) ◽  
pp. 1641025 ◽  
Author(s):  
Ronaldo V. Lobato ◽  
Manuel Malheiro ◽  
Jaziel G. Coelho
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Neutron Stars ◽  
White Dwarf ◽  
Alternative Model ◽  
Gamma Ray ◽  
X Ray ◽  
Surface Magnetic Field ◽  
Rotation Periods ◽  
Strong Surface

The anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs) are a class of pulsars understood as neutron stars (NSs) with super strong surface magnetic fields, namely [Formula: see text][Formula: see text]G, and for that reason are known as magnetars. However, in the last years, some SGRs/AXPs with low surface magnetic fields [Formula: see text]–[Formula: see text][Formula: see text]G have been detected, challenging the magnetar description. Moreover, some fast and very magnetic white dwarfs (WDs) have also been observed, and at least one showed X-ray energy emission as an ordinary pulsar. Following this fact, an alternative model based on WDs pulsars has been proposed to explain this special class of pulsars. In this model, AXPs and SGRs as dense and magnetized WDs can have surface magnetic field [Formula: see text]–[Formula: see text] G and rotate very fast with frequencies [Formula: see text][Formula: see text]rad/s, consistent with the observed rotation periods [Formula: see text]–12)[Formula: see text]s.

scholarly journals AXPs & SGRs: Magnetar or Quarctar?

2012 ◽  
Vol 8 (S291) ◽  
pp. 474-476
Author(s):  
Guojun Qiao ◽  
Xionwei Liu ◽  
Renxin Xu ◽  
Yuanjie Du ◽  
Jinlin Han ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Loss Rate ◽  
Gamma Ray ◽  
Radiation Energy ◽  
X Ray ◽  
Two Factors ◽  
Normal Method ◽  
The Magnetic Field

AbstractThe concept of a “magnetar” was proposed mainly because of two factors. First, the X-ray luminosity of Anomalous X-ray Pulsars (AXPs) and Soft Gamma-Ray Repeaters (SGRs) is larger than the rotational energy loss rate (Lx > Ėrot), and second, the magnetic field strength calculated from “normal method” is super strong. It is proposed that the radiation energy of magnetar comes from its magnetic fields. Here it is argued that the magnetic field strength calculated through the normal method is incorrect at the situation Lx > Ėrot, because the wind braking is not taken into account. Besides, the “anti-magnetar” and some other X-ray and radio observations are difficult to understand with a magnetar model.Instead of the magnetar, we propose a “quarctar”, which is a crusted quark star in an accretion disk, to explain the observations. In this model, the persistent X-ray emission, burst luminosity, spectrum of AXPs and SGRs can be understood naturally. The radio-emitting AXPs, which are challenging the magnetar, can also be explained by the quarctar model.

scholarly journals On the Nature of Magnetars

2004 ◽  
Vol 218 ◽  
pp. 265-266
Author(s):  
Ya. N. Istomin
Keyword(s):  
Magnetic Field ◽  
Neutron Star ◽  
Magnetic Fields ◽  
Electromagnetic Fields ◽  
Gamma Ray ◽  
X Ray ◽  
Surface Magnetic Field ◽  
The Core ◽  
Neutron Star Crust ◽  
High Magnitude

The electromagnetic fields of magnetodipole radiation can penetrate to the conducting matter of a neutron star crust and create there electric currents and tangential magnetic fields of high magnitude. The solution obtained here has the form of surface magnetic field discontinuities propagating through the crust to the core. This model explains the phenomena of magnetars — Soft Gamma-ray Repeaters and Anomalous X-ray Pulsars.

scholarly journals SIMILARITIES OF SGRs WITH LOW MAGNETIC FIELD AND WHITE DWARF PULSARS

2012 ◽  
Vol 18 ◽  
pp. 96-100 ◽  
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.

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 The synchrotron polarization in decaying magnetic field in gamma-ray bursts

2020 ◽  
Vol 498 (3) ◽  
pp. 3492-3502
Author(s):  
K F Cheng ◽  
X H Zhao ◽  
J M Bai
Keyword(s):  
Magnetic Field ◽  
Energy Band ◽  
Large Scale ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Polarization Degree ◽  
Band Spectrum ◽  
Polarization Angle ◽  
Radiation Mechanism

ABSTRACT Polarization can serve as a probe of the radiation mechanism and magnetic field (MF) configuration in gamma-ray bursts (GRBs). In the case of constant MF, the synchrotron polarization in the prompt phase of GRBs has been widely studied. In this paper, we consider the case of the decaying MF. We calculate the time-averaged and instantaneous synchrotron polarizations in a pulse for different viewing angles and for the large-scale decaying MF model, which can explain the so-called Band spectrum. We find that the on-axis time-averaged polarization degree (PD) in the energy band of 50–500 keV for the decaying large-scale MF model (∼0.6 for typical parameters) is higher than that in the constant MF model (∼0.5). An interesting result is the instantaneous PD in the off-axis case will experience a turnover, i.e. the PD will evolve from a positive value to a negative one. This suggests the polarization angle (PA) change by an angle of 90°. Such a result is roughly consistent with the discovery of the PA evolution within a pulse in some bursts, such as GRB 170114A and GRB 160821A. Our result implies at least a part of bursts (off-axis bursts) should have the PA evolution in a pulse.

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