60 research outputs found
Energy Extraction and Particle Acceleration Around Rotating Black Hole in Horava-Lifshitz Gravity
Penrose process on rotational energy extraction of the black hole (BH) in the
original non-projectable Ho\v{r}ava-Lifshitz gravity is studied. The strong
dependence of the extracted energy from the special range of parameters of the
Ho\v{r}ava-Lifshitz gravity, such as parameter and specific angular
momentum has been found. Particle acceleration near the rotating BH in
Ho\v{r}ava-Lifshitz gravity has been studied. It is shown that the fundamental
parameter of the Ho\v{r}ava-Lifshitz gravity can impose limitation on the the
energy of the accelerating particles preventing them from the infinite value.Comment: 6 pages, 3 figures, accepted for publication in Physical Review
Scalar perturbations and quasi-normal modes of a non-linear magnetic-charged black hole surrounded by quintessence
We study scalar perturbations and quasinormal modes of a nonlinear magnetic
charged black hole surrounded by quintessence. Time evolution of scalar
perturbations is studied for different parameters associated with the black
hole solution. We also study the reflection and transmission coefficients along
with absorption cross-section for the considered black hole spacetime. It was
shown that the real part of quasinormal frequency increases with increase in
nonlinear magnetic charge while the module of the imaginary part of the
frequency decreases. The analysis of the perturbations with changing
quintessential parameter showed that perturbations with high values of
become unstable.Comment: 11 pages, 12 figures. v2: refereed versio
Gravitational lensing for a boosted Kerr black hole in the presence of plasma
We obtain the deflection angle for a boosted Kerr black hole in the weak
field approximation. We also study the behavior of light in the presence of
plasma by considering different distributions: singular isothermal sphere,
non-singular isothermal gas sphere, and plasma in a galaxy cluster. We find
that the dragging of the inertial system along with the boosted parameter
affect the value of the deflection angle. As an application, we
studied the magnification for both uniform and SIS distributions.Comment: 20 pages, 17 figures. v2: refereed versio
External Electromagnetic Fields of a Slowly Rotating Magnetized Star with Gravitomagnetic Charge
We study Maxwell equations in the external background spacetime of a slowly
rotating magnetized NUT star and find analytical solutions for the exterior
electric fields after separating the equations of electric field into angular
and radial parts in the lowest order approximation. The star is considered
isolated and in vacuum, with dipolar magnetic field aligned with the axis of
rotation. The contribution to the external electric field of star from the NUT
charge is considered in detail.Comment: 6 pages, 2 figures, accepted for publication in Astrophysics and
Space Scienc
Electromagnetic Fields of Slowly Rotating Magnetized Gravastars
We study the dipolar magnetic field configuration and present solutions of
Maxwell equations in the internal background spacetime of a a slowly rotating
gravastar. The shell of gravastar where magnetic field penetrated is modeled as
sphere consisting of perfect highly magnetized fluid with infinite
conductivity. Dipolar magnetic field of the gravastar is produced by a circular
current loop symmetrically placed at radius at the equatorial plane.Comment: 5 pages, 2 figures, accepted for publication to Mod. Phys. Lett.
Qualifying ringdown and shadow of black holes under general parametrized metrics with photon orbits
The motion of photons around black holes determines the shape of shadow and
match the ringdown properties of a perturbed black hole. Observations of
shadows and ringdown waveforms will reveal the nature of black holes. In this
paper, we study the motion of photons in a general parametrized metric beyond
the Kerr hypothesis. We investigated the radius and frequency of the photon
circular orbits on the equatorial plane and obtained fitted formula with varied
parameters. The Lyapunov exponent which connects to the decay rate of the
ringdown amplitude is also calculated. We also analyzed the shape of shadow
with full parameters of the generally axisymmetric metric. Our results imply
the potential constraint on black hole parameters by combining the Event
Horizon Telescope and gravitational wave observations in the future.Comment: 18 pages, 27 figure
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