arXiv subjects

Sangita Chatterjee

Publications and source records attributed to Sangita Chatterjee.

3 recordsLinked to original sources

arXiv2026

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↗

arXiv2026

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↗

arXiv2023

Ideal E/IMRI vs Real E/IMRI system : Observable signature in LISA

Real extreme/intermediate mass ratio inspiral(E/IMRI) systems are likely to contain large accretion disks which could be as massive as the central supermassive black hole. Therefore, contrary to its ideal model, a real E/IMRI system contains a third important component: the accretion disk. We study the influence of these disks on the emitted GW profile and its detectability through proposed LISA observation. We use a semi-relativistic formalism in the Kerr background (Gair & Glampedakis 2006; Barausse & Rezzolla 2008) for the case of transonic accretion flow which is a potential candidate to describe the accretion flows around AGN. The hydrodynamic drag of the disks modified the motion of the companion as a result the emitted wave changes in amplitude and phase. We found that these changes are detectable through the last few years of observation by LISA (in some cases as small as six months) for EMRIs residing within 3 GPc from the detector and for the accretion rate of the primary black hole of the order of $\dot{M}=1 \dot{M}_{Edd}$. These choices of parameter values are consistent with real systems. The drag effect and hence the detectability of the emitted GW is sensitive to the hydrodynamical model of the disk. Therefore such observations will help one to identify the nature of the accretion flow and verify various paradigms of accretion physics.

astro-ph.HE↗