SearcharxivSearch

arXiv subjects

Ripon Sk

Publications and source records attributed to Ripon Sk.

4 recordsLinked to original sources

Transonic accretion and the analogue gravity in multi-component elliptical galaxies hosting pseudo-Schwarzschild black holes

Low-angular-momentum, axisymmetric, inviscid accretion flows onto a black hole have been studied using the vertical equilibrium disc model, considering multiple pseudo-Schwarzschild potentials and two thermodynamic equations of state. A multi-component galactic potential-representing stellar, dark matter, and hot-gas contributions-is incorporated to assess environmental effects on the accretion dynamics. In our earlier work, it is found that the effect of multi-component galactic potential on the accretion flow onto a rotating black hole under similar framework of analysis, significantly varies over different standard disc models, being most pronounced in the vertical equilibrium (VE) disc model. Thus it may be interesting to find whether such variation occur for different choices of pseudo potentials too. To begin with, in this work we consider accretion flow onto a non-rotating blackhole with VE geometry. Through the analysis of transonic behaviour and eigenvalue-based critical point classification, we demonstrate that, for all selected black hole potentials, the galactic potential profoundly influences the locations of critical points, the shock-allowed parameter space, shock-location, shock-driven flow variables, and acoustic surface gravity.

astro-ph.HE

On the spin dependence of the emergent gravity phenomena as observed in axially symmetric black hole accretion with spatially varying adiabatic index

The present work addresses an axisymmetrically accreting black hole system from three perspectives: the astrophysical, the dynamical systems, and the emergent gravity standpoint. Steady-state equations governing low angular momentum axially symmetric accretion under a pseudo-Kerr potential are formulated for a multi-species flow with a spatially varying adiabatic index. The resulting transonic solutions are shown to be multi-transonic and may accommodate a stationary shock. Critical points are classified via perturbative dynamical systems methods, and linear stability analysis confirms that the stationary solutions remain stable under radial perturbation. The ensuing acoustic geometry harbours acoustic black holes at the sonic points and an acoustic white hole at the shock location, whose causal structure is constructed via the Carter--Penrose diagram. The surface gravity associated with each acoustic horizon is computed using a generalized expression that accounts for the spatial variation of the local sound speed.

astro-ph.HE

Model-Dependent Galactic Environment Effects on Multi-Transonic Accretion and Emergent Acoustic Gravity around Kerr Black Holes

The hydrodynamics of low angular momentum, multi-transonic, axisymmetric, inviscid accretion flow onto a rotating black hole in presence of a galactic environment has been systematically investigated in detail using three standard disc geometries and two thermodynamic equations of state, within the post-Newtonian framework with a pseudo-potential. In addition to the influence of a centrally located black hole, this study incorporates those due to a multi-component galactic environment -- stellar matter, dark matter, and hot gas. Our analysis reveals that the extent of additional influence of the galactic environment on accretion flow depends severely on the disc model chosen. This effect is particularly pronounced in the vertical equilibrium disc model, whereas it is extremely mild for other two geometries. The same is observed for location of sonic points, parameters related to multi-transonicity and shock formation, and also for the emergent analogue surface gravity calculated. Another observation is that, among different components of galactic environment, contribution of dark matter is most dominant, followed by a mild one due to hot gas; while that due to stellar matter is even milder in determining the flow. The stationary flow characteristics are analysed using semi-analytical numerical methods including the method analogous to critical point analysis used in dynamical systems. Additionally, a time-dependent linear perturbation analysis ensures the stability of stationary accretion flow in all cases, and hence the corresponding acoustic metric and acoustic surface gravity are derived.

astro-ph.HE

Motion of charged particle in Reissner-Nordstrom spacetime: A Jacobi metric approach

The present work discusses motion of neutral and charged particles in Reissner - Nordstrom spacetime. The constant energy paths are derived in a variational principle framework using the Jacobi metric which is parameterized by conserved particle energy. Of particular interest is the case of particle charge and Reissner-Nordstrom black hole charge being of same sign since this leads to a clash of opposing forces - gravitational (attractive) and Coulomb (repulsive). Our paper aims to compliment the recent works of Pugliese, Quevedo and Ruffini [1,2]. The energy dependent Gaussian curvature (induced by Jacobi metric), plays an important role in classifying the trajectories.

gr-qc