Publications (8)0 Total impact
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Article: Shadow of Kerr-Taub-NUT black hole
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ABSTRACT: The shadow of a rotating black hole with nonvanishing gravitomagnetic charge has been studied. It was shown that in addition to the angular momentum of black hole the gravitomagnetic charge term deforms the shape of the black hole shadow. From the numerical results we have obtained that for a given value of the rotation parameter, the presence of a gravitomagnetic charge enlarges the shadow and reduces its deformation with respect to the spacetime without gravitomagnetic charge. Finally we have studied the capture cross section for massive particles by black hole with the nonvanishing gravitomagnetic charge.12/2012; -
Article: Particle acceleration in the polar cap region of an oscillating neutron star
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ABSTRACT: We revisit particle acceleration in the polar cap region of a neutron star by taking into account both general relativistic effects and the presence of toroidal oscillations at the star surface. In particular, we address the question of whether toroidal oscillations at the stellar surface can affect the acceleration properties in the polar cap. We solve numerically the relativistic electrodynamics equations in the stationary regime, focusing on the computation of the Lorentz factor of a space-charge-limited electron flow accelerated in the polar cap region of a rotating and oscillating pulsar. To this extent, we adopt the correct expression of the general relativistic Goldreich-Julian charge density in the presence of toroidal oscillations. Depending on the ratio of the actual charge density of the pulsar magnetosphere to the Goldreich-Julian charge density, we distinguish two different regimes of the Lorentz factor of the particle flow, namely an oscillatory regime produced for sub-GJ current density configurations, which does not produce an efficient acceleration, and a true accelerating regime for super-GJ current density configurations. We find that star oscillations may be responsible for a significant asymmetry in the pulse profile that depends on the orientation of the oscillations with respect to the pulsar magnetic field. In particular, significant enhancements of the Lorentz factor are produced by stellar oscillations in the super-GJ current density regime.11/2011; -
Article: Energy Extraction and Particle Acceleration Around Rotating Black Hole in Horava-Lifshitz Gravity
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ABSTRACT: 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 $\Lambda_W$ and specific angular momentum $a$ 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.07/2011; -
Article: Explaining radio emission of magnetars via rotating and oscillating magnetospheres of neutron stars
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ABSTRACT: We investigate the conditions for radio emission in rotating and oscillating magnetars, by focusing on the main physical processes determining the position of their death-lines in the P-\dot{P} diagram, i.e. of those lines that separate the regions where the neutron star may be radio-loud or radio-quiet. After using the general relativistic expression for the electromagnetic scalar potential in the magnetar magnetosphere, we find that larger compactness parameters of the star as well as larger inclination angles between the rotation axis and the magnetic moment produce death-lines well above the majority of known magnetars. This is consistent with the observational evidence of no regular radio emission from the magnetars in the frequency range typical for the ordinary pulsars. On the contrary, when oscillations of the magnetar are taken into account, the death-lines shift downward and the conditions necessary for the generation of radio emission in the magnetosphere are met. Present observations showing a close connection between the burst activity of magnetars and the generation of the radio emission in the magnetar magnetosphere are naturally accounted for within our interpretation.07/2011; -
Article: Magnetized Particle Capture Cross Section for Braneworld Black Hole
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ABSTRACT: Capture cross section of magnetized particle (with nonzero magnetic moment) by braneworld black hole in uniform magnetic field is considered. The magnetic moment of particle was chosen as it was done by \citet{rs99} and for the simplicity particle with zero electric charge is chosen. It is shown that the spin of particle as well as the brane parameter are to sustain the stability of particles circularly orbiting around the black hole in braneworld i.e. spin of particles and brane parameter try to prevent the capture by black hole.05/2011; -
Article: Particle motion around black hole in Hořava-Lifshitz gravity
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ABSTRACT: Analytical solutions of Maxwell equations around black hole immersed in external uniform mag-netic field in the background of the Kehagias-Sfetsos (KS) asymptotically flat black hole solution of Hořava-Lifshitz gravity have been found. Influence of magnetic field on effective potential of the radial motion of charged test particle around black hole immersed in external magnetic field in Hořava-Lifshitz gravity has been investigated by using Hamilton-Jacobi method. Exact analytical solution for dependence of the minimal radius of the circular orbits rmc from KS parameter ω for motion of test particle around spherical symmetric black hole in Hořava-Lifshitz gravity has been derived. The critical values of the particle's angular momentum for captured particles by black hole in Hořava-Lifshitz gravity have been obtained numerically. The comparison of the obtained numerical results with the astrophysical observational data on radii of the innermost stable circular orbits gives us the estimation of the parameter as ω ≃ 3.6 · 10 −24 cm −2 .02/2011; -
Article: Electromagnetic Fields of Slowly Rotating Compact Magnetized Stars in Braneworld
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ABSTRACT: We study the structure of electromagnetic field of slowly rotating magnetized star in a Randall-Sundrum II type braneworld. The star is modeled as a sphere consisting of perfect highly magnetized fluid with infinite conductivity and frozen-in dipolar magnetic field. Maxwell's equations for the external magnetic field of the star in the braneworld are analytically solved in approximation of small distance from the surface of the star. We have also found numerical solution for the electric field outside the rotating magnetized neutron star in the braneworld in dependence on brane tension. The influence of brane tension on the electromagnetic energy losses of the rotating magnetized star is underlined. Obtained "brane" corrections are shown to be relevant and have non-negligible values. In comparison with astrophysical observations on pulsars spindown data they may provide an evidence for the brane tension and, thus, serve as a test for the braneworld model of the Universe. Comment: 11 pages, 5 figures12/2010; -
Article: Test particle motion around a black hole in a braneworld
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ABSTRACT: Analytical solutions of Maxwell equations in background spacetime of a black hole in a braneworld immersed in an external uniform magnetic field have been found. The influence of both magnetic and brane parameters on the effective potential of the radial motion of a charged test particle around a slowly rotating black hole in a braneworld immersed in a uniform magnetic field has been investigated by using the Hamilton-Jacobi method. An exact analytical solution for dependence of the radius of the innermost stable circular orbits (ISCO) rISCO from the brane parameter for the motion of a test particle around a nonrotating isolated black hole in a braneworld has been derived. It has been shown that the radius rISCO is monotonically growing with the increase of the module of the brane tidal charge. A comparison of the predictions on rISCO of the braneworld model and of the observational results of ISCO from relativistic accretion disks around black holes provided the upper limit for the brane tidal charge ≲109 cm2.Phys. Rev. D. 05/2009; 81(4).
