arXiv subjects

Shokoufe Faraji

Publications and source records attributed to Shokoufe Faraji.

25 records · Page 2Linked to original sources

arXiv2022

Dynamics of charged particles and quasi-periodic oscillations in the vicinity of a distorted, deformed compact object embedded in a uniform magnetic field

This work presents the dynamic properties of charged test particles influenced by the gravitational and electromagnetic fields. Accordingly, in this work, we concentrate on the static and axially symmetric metric containing two quadrupole parameters. One relates to the central object, and another relates to the external distribution of matter. This metric may associate the observable effects to these parameters as dynamical degrees of freedom. The astrophysical motivation for choosing such a field is the possibility to constitute a reasonable model for an actual situation occurring in the objects' vicinity. To test the role of large-scale magnetic fields in accretion processes, we start by analyzing different bound orbits of timelike orbits under the influence of the system's different parameters. This leads to examining their stability concerning radial and/or vertical oscillations. The main focus is to discuss the effect of magnetic field on the oscillation modes' resonant phenomena using different resonant models for disc-oscillation modes. In the present contribution, we further explore the possibility of relating oscillatory frequencies of charged particles to the frequencies of the high-frequency quasi-periodic oscillations observed in the microquasars GRS 1915+105, XTE 1550-564 and GRO 1655-40 via assuming the relevance of resonant phenomena of the radial and vertical oscillations.

astro-ph.HE↗

arXiv2022

Circular geodesics in a New Generalization of q-metric

This paper introduces an alternative generalization of the static solution with quadrupole moment, the $\rm q$-metric, that describes a deformed compact object in the presence of the external fields characterized by multipole moments. In addition, we also examine the impact of the external fields up to quadrupole on the circular geodesics and the interplay of these two quadrupoles on the place of the innermost stable circular orbit (ISCO) in the equatorial plane.

gr-qc↗

arXiv2021

Magnetized tori in the background of a deformed compact object

This paper studied the relativistic accretion thick disc model raised by a deformed compact object that slightly deviated from spherical up to the quadrupole moment by utilising $\rm q$-metric. This metric is the simplest asymptotically flat solution of Einstein's equation with quadrupole moment. This work aims to study the effects of quadrupole moments in combination with the parameters of the thick magnetised disc model via studying the properties of these equilibrium sequences of magnetised, non-self-gravitating discs in this space-time. We employed different angular momentum distributions and discussed the procedure of building this toroidal disc model based on a combination of approaches previously considered in the literature. We have shown the properties of this relativistic accretion disc model and its dependence on the initial parameters. Besides, this theoretical model can be served as the initial data for numerical simulations.

astro-ph.HE↗

arXiv2021

Effect of an external mass distribution on the magnetized accretion disk

In this paper, we constructed the magnetized thick disk model analytically around the static black hole in the presence of an external distribution of matter up to the quadrupole moment. This space-time is a solution to Einstein's field equation describing the exterior of a static and axially symmetric object locally. This work aims to study this space-time and the effects of quadrupole moments via studying the properties of the equilibrium sequences of magnetized, non-self-gravitating disks in this space-time. We discussed a procedure to build the thick disk model based on a combination of two approaches previously considered in the literature. We have examined different angular momentum distributions, and We have shown the properties of this relativistic accretion disc model in this background.

astro-ph.HE↗

arXiv2021

Thin accretion disk around the distorted Schwarzschild black hole

We construct the relativistic standard steady, optically thick, cold and geometrically thin accretion disk around a distorted Schwarzschild black hole. The distortion of this static and axially symmetric black hole solution, is connected to an external distribution of matter. If the effects due to the rotation are negligible, this distribution can describe the exterior of any axially symmetric astrophysical model. Also, the distortion could be related to the outer parts of the accretion disk. We study the effects due to a distortion up to the quadrupole, and compare the physical characteristics of this disk to the usual Schwarzschild case.

astro-ph.HE↗

arXiv2021

Quasi-periodic oscillatory motion of particles orbiting a distorted deformed compact object

This work explores the dynamic properties of test particles surrounding a distorted, deformed compact object. The astrophysical motivation was to choose such background, which could constitute a more reasonable model of a real situation that arises in the vicinity of compact objects with the possibility of having parameters as the extra physical degrees of freedom. This can facilitate associating observational data with astrophysical systems. This work's main goal is to study the dynamic regime of motion and quasi-periodic oscillation in this background, depending on different parameters of the system. Also, we exercise the resonant phenomena of the radial and vertical oscillations at their observed quasi-periodic oscillations frequency ratio of 3:2.

astro-ph.HE↗

arXiv2020

Structure of the thin disk in the background of a distorted naked singularity versus a distorted static black hole

We consider the standard relativistic geometrically thin and optically thick accretion disc around a distorted static black hole and a distorted naked singularity. The distortion is the result of the existence of a static axisymmetric external distribution of matter via exercising quadrupole moments. Our main purpose of this work is to investigate whether the naked singularity models have their own observational fingerprint if they do exist. In fact, understanding the astrophysical behavior of naked singularities seems to be extremely important in the perspective of general relativity and understanding of black hole physics today.

astro-ph.HE↗