Polarization distribution in the image of a synchrotron emitting ring around regular black holes

Abstract

We have studied the polarized image of a synchrotron emitting ring around regular Hayward black hole and Bardeen black hole, respectively. Each of them carries a magnetic field itself in terms of gravity coupled to a nonlinear electrodynamics. Our results show that the main features of the polarization images of emitting rings are similar in these two regular black hole spacetimes. With the increase of magnetic charge parameter, the polarization intensity and electric vector position angle in the image plane increase in both Hayward black hole and Bardeen black hole spacetimes. We also investigate the differences of polarization intensity and electric vector position angle between in the regular black hole spacetime and in the Schwarzschild case, which indicates that the differences in the Hayward black hole spacetime are smaller than those in the Bardeen black hole. We also find the effects of the magnetic charge parameter on the Strokes Q − U loops slightly larger in Bardeen black hole spacetime. These information stored in the polarization image around Hayward and Bardeen black holes could help us to understand regular black holes and the gravity coupled a nonlinear electrodynamics.

Polarized image of a rotating black hole in Scalar-Tensor-Vector-Gravity theory

“…The photon polarization vector at the source f µ in Boyer-Linquist coordinates can be computed through the transformation (13). With the angle ζ between p the magnetic field B…”

“…Moreover, the analysis show that the polarization patterns depend also on the strongly curved spacetime near the black holes. Thus, study of polarized images of black holes is beneficial to probe the matter distribution and the related physical process around black holes [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], even check theories of gravity.…”

“…Moreover, with this model, the image of a finite thin disk can be produced by simply summing contributions from individual radii [26,27]. Thus, this model has been recently applied to study the polarized image of an equatorial emitting ring in various spacetimes, such as, 4D Gauss-Bonnet black hole [12], regular black holes [13], Schwarzschilld-Melvin black hole [16], and so on.…”

Image of Bonnor black dihole with a thin accretion disk and its polarization information

“…Although only the emission within a narrow range of radii R is considered in this simple model, it clearly reveals that the polarization signatures are dominated by magnetic field configuration, black hole spin and observer inclination. With this model, the polarized image of an equatorial emitting ring has been studied for 4D Gauss-Bonnet black hole [17] and regular black holes [18]. The polarized distribution of the image originating from synchrotron radiations of the charged point particle in curved spacetime has been investigated in [19,20].…”

“…Moreover, we note that the intensity of the secondary image is stronger than that of the direct image when θ 0 = 30 • , which differs from that in the case θ 0 = 60 • . It is understandable by a fact that the intensity I of image(18) arising from synchrotron radiation depends on not only the angle ζ, but also on the redshift factor g in the propagation of photon from the source in the disk to the observer. From (6), the value of ζ corresponded to the direct image is less than that of the secondary image in the both cases θ 0 = 30 • and θ 0 = 60 • .…”