Jan Schee
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View article: Oscillatory Behaviors in General Relativistic Magnetohydrodynamical Simulations of Interacting Toroids
Oscillatory Behaviors in General Relativistic Magnetohydrodynamical Simulations of Interacting Toroids Open
Oscillatory behavior in the total flux emitted from both single and double torus structures was observed in our general relativistic magnetohydrodynamical simulations performed using the High-Accuracy Astrophysical Relativistic MHD code. T…
View article: Primary Proca Hair and the Double-Peak Optics of Black Holes
Primary Proca Hair and the Double-Peak Optics of Black Holes Open
We study the optical properties of black holes endowed with primary Proca hair, focusing on the distinctive double-peak structure generated in the effective potential by the massive vector field. This novel feature drastically modifies the…
View article: Light curve of a hotspot on equatorial orbit around Kerr black hole surrounded by reflective firewall
Light curve of a hotspot on equatorial orbit around Kerr black hole surrounded by reflective firewall Open
The light curve of an isolated bright spot in a Keplarian orbit is studied to investigate the signature of the firewall around the event horizon of the black hole. An increase in total observed flux is found. In addition to that, for firew…
View article: Temperature Anisotropy of the CMBR and the Non-zero Cosmological Constant
Temperature Anisotropy of the CMBR and the Non-zero Cosmological Constant Open
We analyze the effect of a spherically symmetric clump on the anisotropy of the cosmic microwave background radiation temperature in the framework of the standard model of cosmology with a non-zero cosmological constant $Λ$ and we show tha…
View article: Appearance of Keplerian discs orbiting on both sides of a reflection-symmetric wormhole
Appearance of Keplerian discs orbiting on both sides of a reflection-symmetric wormhole Open
We construct optical appearance and profiled spectral lines of Keplerian discs with inner edge at the innermost circular geodesic located on both sides of the reflection-symmetric Simpson-Visser wormhole, in dependence on its parameter and…
View article: Strong gravitational lensing around Kehagias-Sfetsos compact objects surrounded by plasma
Strong gravitational lensing around Kehagias-Sfetsos compact objects surrounded by plasma Open
We present the analysis how Hořava gravity and plasma influence the strong lensing phenomena around Kehagias-Sfetsos (KS) black holes. Using the semi-analytical Bozza method of strong lensing limit, we determine the multiple images, namely…
View article: Light curves of the hot spots on circular orbits around generic regular black holes related to non-linear electrodynamics with Maxwellian weak-field Limit
Light curves of the hot spots on circular orbits around generic regular black holes related to non-linear electrodynamics with Maxwellian weak-field Limit Open
The combined effect of a strong gravitational field and electromagnetic field in the vicinity of a generic regular black hole related to non-linear electrodynamics with Maxwellian weak-field limit on the radiation flux of a hot spot orbiti…
View article: Shadow of the magnetically and tidally deformed black hole
Shadow of the magnetically and tidally deformed black hole Open
We consider a simple model of a black hole surrounded by a toroidal structure and experiencing deformation due to magnetic field and the tidal force. For this system we construct the shadows of Preston-Poisson black hole, apply it to super…
View article: Generic Regular Black Holes Related to Nonlinear Electrodynamics with Maxwellian Weak-field Limit: Shadows and Images of Keplerian Disks
Generic Regular Black Holes Related to Nonlinear Electrodynamics with Maxwellian Weak-field Limit: Shadows and Images of Keplerian Disks Open
We study optical phenomena in generic regular, magnetically charged, spherically symmetric black hole spacetimes arising from coupling of the Einstein gravity and nonlinear electrodynamics (NED) with the Maxwellian weak-field limit, where …
View article: Gravitational lensing around Kehagias-Sfetsos compact objects surrounded by plasma
Gravitational lensing around Kehagias-Sfetsos compact objects surrounded by plasma Open
We study the optical properties of the Kehagias-Sfetsos (KS) compact objects, characterized by the "Hořava" parameter $ω_{_{KS}}$, in the presence of plasma, considering its homogeneous or power-law density distribution. The strong effects…
View article: Effective Geometry of the Bardeen Spacetimes: Gravitational Lensing and Frequency Mapping of Keplerian Disks
Effective Geometry of the Bardeen Spacetimes: Gravitational Lensing and Frequency Mapping of Keplerian Disks Open
We study the appearance of Keplerian accretion disks in order to demonstrate the influence of the nonlinear electrodynamics (NED) on the gravitational lensing and frequency shifting of the images of the Keplerian disks. We focus our attent…
View article: Electromagnetic perturbations of black holes in general relativity coupled to nonlinear electrodynamics
Electromagnetic perturbations of black holes in general relativity coupled to nonlinear electrodynamics Open
The electromagnetic (EM) perturbations of the black hole solutions in general relativity coupled to nonlinear electrodynamics (NED) are studied for both electrically and magnetically charged black holes, assuming that the EM perturbations …
View article: Particle collisions and optical effects in the mining Kerr-Newman spacetimes
Particle collisions and optical effects in the mining Kerr-Newman spacetimes Open
We study ultra-high-energy particle collisions and optical effects in the\nextraordinary class of mining braneworld Kerr-Newman (KN) naked singularity\nspacetimes, predicting extremely high efficiency of Keplerian accretion, and\ncompare t…
View article: Scalar perturbations of nonsingular nonrotating black holes in conformal gravity
Scalar perturbations of nonsingular nonrotating black holes in conformal gravity Open
We study scalar and electromagnetic perturbations of a family of nonsingular nonrotating black hole spacetimes that are solutions in a large class of conformally invariant theories of gravity. The effective potential for scalar perturbatio…
View article: Quasinormal frequencies of black hole in the braneworld
Quasinormal frequencies of black hole in the braneworld Open
We have studied scalar, electromagnetic and gravitational perturbations of the four-dimensional Reissner-Nordstr\"{o}m-like black holes with a \textit{tidal charge} in the Randall-Sundrum braneworld. The quasinormal modes of these scalar, …
View article: Profiled spectral lines generated by Keplerian discs orbiting in the Bardeen and Ayòn-Beato–Garcìa spacetimes
Profiled spectral lines generated by Keplerian discs orbiting in the Bardeen and Ayòn-Beato–Garcìa spacetimes Open
Shape and frequency-shift map of direct and indirect images of Keplerian\ndiscs orbiting in Bardeen and Ayon-Beato-Garcia (ABG) black hole and no-horizon\nspacetimes are determined. Then profiles of spectral lines generated in the\ninnermo…