scholarly journals The magnetic field structure in CTA 102 from high-resolution mm-VLBI observations during the flaring state in 2016–2017

2019 ◽  
Vol 622 ◽  
pp. A158 ◽  
Author(s):  
Carolina Casadio ◽  
Alan P. Marscher ◽  
Svetlana G. Jorstad ◽  
Dmitry A. Blinov ◽  
Nicholas R. MacDonald ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Faraday Rotation ◽  
High Energy ◽  
Field Structure ◽  
Physical Processes ◽  
Magnetic Field Structure ◽  
The Core ◽  
Doppler Factor ◽  
High Energy Emission ◽  
The Magnetic Field

Context. Investigating the magnetic field structure in the innermost regions of relativistic jets is fundamental to understanding the crucial physical processes giving rise to jet formation, as well as to their extraordinary radiation output up to γ-ray energies. Aims. We study the magnetic field structure of the quasar CTA 102 with 3 and 7 mm VLBI polarimetric observations, reaching an unprecedented resolution (∼50 μas). We also investigate the variability and physical processes occurring in the source during the observing period, which coincides with a very active state of the source over the entire electromagnetic spectrum. Methods. We perform the Faraday rotation analysis using 3 and 7 mm data and we compare the obtained rotation measure (RM) map with the polarization evolution in 7 mm VLBA images. We study the kinematics and variability at 7 mm and infer the physical parameters associated with variability. From the analysis of γ-ray and X-ray data, we compute a minimum Doppler factor value required to explain the observed high-energy emission. Results. Faraday rotation analysis shows a gradient in RM with a maximum value of ∼6 × 104 rad m−2 and intrinsic electric vector position angles (EVPAs) oriented around the centroid of the core, suggesting the presence of large-scale helical magnetic fields. Such a magnetic field structure is also visible in 7 mm images when a new superluminal component is crossing the core region. The 7 mm EVPA orientation is different when the component is exiting the core or crossing a stationary feature at ∼0.1 mas. The interaction between the superluminal component and a recollimation shock at ∼0.1 mas could have triggered the multi-wavelength flares. The variability Doppler factor associated with such an interaction is large enough to explain the high-energy emission and the remarkable optical flare occurred very close in time.

scholarly journals Modeling of pulsar magnetospheres

2012 ◽  
Vol 8 (S291) ◽  
pp. 291-291
Author(s):  
Anatoly Spitkovsky
Keyword(s):  
Magnetic Field ◽  
High Energy ◽  
Field Structure ◽  
Emission Region ◽  
Magnetic Field Structure ◽  
Resistive Force ◽  
Model Predictions ◽  
The Status ◽  
High Energy Emission ◽  
Vacuum Space

AbstractThe inner workings of pulsar magnetospheres have fascinated and confused researchers since the discovery of pulsars. I will review the status of magnetospheric models, including vacuum, space-charge-limited and resistive force-free MHD. I will highlight model predictions for the integrated pulsar quantities (such as spin down and torques) and the observational consequences of calculated magnetic field structure. Particularly, high-energy emission from pulsars allows putting new constraints on the geometry of the emission region and the physics of particle acceleration in the magnetosphere.

scholarly journals The magnetic field structure in the multi-source magnetized core NGC 2024 FIR 5

2008 ◽  
Vol 4 (S259) ◽  
pp. 53-60
Author(s):  
Felipe de O. Alves ◽  
J. M. Girart ◽  
S.-P. Lai ◽  
R. Rao ◽  
Q. Zhang
Keyword(s):  
Magnetic Field ◽  
Dust Emission ◽  
Field Structure ◽  
Magnetic Field Structure ◽  
The Core ◽  
Evolutionary Scenario ◽  
Field Geometry ◽  
Field Lines ◽  
Grain Properties ◽  
The Magnetic Field

AbstractThis work reports high resolution SMA polarimetric observations toward NGC 2024 FIR 5, a magnetized core previously found to harbour protostars. Our 345 GHz data indicates the presence of an extended dust emission associated with the dense core where the protostars are embedded. The 3σ polarized intensity shows depolarization toward the peak of Stokes I emission. This diminishing polarized flux implies that the alignment efficiency of the core dust grains is low within higher column densities where grain properties are likely different. The derived magnetic field geometry exhibits pinched field lines which are typical in evolved supercritical clouds where the magnetic field no longer support the core from collapsing. As a consequence for protostars, the gravitational pulling along the disk's long axis makes an equatorial bend to the field lines that, in turn, results in a hourglass shape. The SMA field structure agrees perfectly with the BIMA map. However, models are still necessary to provide a complete description of the evolutionary scenario of FIR 5.

scholarly journals Inferences About the Magnetic Field Structure of a CME with Both In Situ and Faraday Rotation Constraints

2020 ◽  
Vol 896 (2) ◽  
pp. 99
Author(s):  
Brian E. Wood ◽  
Samuel Tun-Beltran ◽  
Jason E. Kooi ◽  
Emil J. Polisensky ◽  
Teresa Nieves-Chinchilla
Keyword(s):  
Magnetic Field ◽  
Faraday Rotation ◽  
Field Structure ◽  
Magnetic Field Structure ◽  
The Magnetic Field

scholarly journals Gamma-ray pulsar light curves as probes of magnetospheric structure

2016 ◽  
Vol 82 (3) ◽  
Author(s):  
A. K. Harding
Keyword(s):  
Magnetic Field ◽  
Gamma Ray ◽  
High Energy ◽  
Field Structure ◽  
Light Curves ◽  
Pulsar Magnetosphere ◽  
Magnetic Field Structure ◽  
Energy Emission ◽  
Emission Models ◽  
High Energy Emission

The large number of ${\it\gamma}$-ray pulsars discovered by the Fermi Gamma-Ray Space Telescope since its launch in 2008 dwarfs the handful that were previously known. The variety of observed light curves makes possible a tomography of both the ensemble-averaged field structure and the high-energy emission regions of a pulsar magnetosphere. Fitting the ${\it\gamma}$-ray pulsar light curves with model magnetospheres and emission models has revealed that most of the high-energy emission, and the particles acceleration, takes place near or beyond the light cylinder, near the current sheet. As pulsar magnetosphere models become more sophisticated, it is possible to probe magnetic field structure and emission that are self-consistently determined. Light curve modelling will continue to be a powerful tool for constraining the pulsar magnetosphere physics.

scholarly journals The Magnetic Be Star Sigma Orionis E

1987 ◽  
Vol 92 ◽  
pp. 82-83 ◽  
Author(s):  
C. T. Bolton ◽  
A. W. Fullerton ◽  
D. Bohlender ◽  
J. D. Landstreet ◽  
D. R. Gies
Keyword(s):  
Magnetic Field ◽  
Field Structure ◽  
High Signal ◽  
Rotational Period ◽  
Magnetic Field Structure ◽  
The Past ◽  
Distribution Of Elements ◽  
Be Star ◽  
Hα Emission ◽  
The Magnetic Field

Over the past two years, we have obtained high resolution high signal/noise (S/N) spectra of the magnetic Be star σ Ori E at the Canada-France-Hawaii Telescope and McDonald Observatory. These spectra, which cover the spectral regions 399-417.5 and 440-458.5 nm and the Hα line and have typical S/N>200 and spectral resolution ≃0.02 nm, were obtained at a variety of rotational phases in order to study the magnetic field structure, the distribution of elements in the photosphere, and the effects of the magnetic field on the emission envelope. Our analysis of these spectra confirms, refines and extends the results obtained by Landstreet & Borra (1978), Groote & Hunger (1982 and references therein), and Nakajima (1985).The Hα emission is usually double-peaked, but it undergoes remarkable variations with the 1.19081 d rotational period of the star, which show that the emitting gas is localized into two regions which co-rotate with the star.

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