Bondi accretion disk luminosity around neutral and charged Simpson-Visser spacetimes

TL;DR

This paper studies how accretion disk luminosity around Simpson-Visser spacetimes varies with different parameters, revealing that the spacetime's regularization and charge significantly influence accretion dynamics and potential observational signatures.

Contribution

It provides a detailed analysis of relativistic Bondi accretion in Simpson-Visser spacetimes, exploring the effects of the regularization parameter and charge on accretion properties and luminosities.

Findings

Critical radius and accretion rates vary with spacetime parameters.

Different fluid models show distinct outer region behaviors.

Charge introduces modest shifts in sonic radius and inflow velocities.

Abstract

We investigate relativistic Bondi accretion in the Simpson-Visser spacetime, which, via a single parameter $\ell$, interpolates between the Schwarzschild, regular black hole, extremal and wormhole regimes. First, we analyze the neutral Simpson-Visser geometry, recovering Schwarzschild at $\ell=0$, and then its charged extension of the Reissner-Nordstr\"om metric. In both these cases, we derive the conservation equations and analyze two representative fluid models: a barotropic perfect fluid and a constituent with an exponential density profile. By varying the parameters across regimes, we locate critical (sonic) points and integrate velocity, density and pressure profiles. While near-horizon inflow velocities are similar across the different solutions, we find that the critical radius and the resulting accretion rates and luminosities severely change, depending on the value of the parameter and type of fluid. Remarkably, the barotropic and exponential cases exhibit different trends in the outer regions. Moreover, by extending the analysis to the charged SV spacetime, we find that the presence of a central charge $Q$ produces additional, albeit modest, shifts in the sonic radius which, in combination with those induced by the regularization parameter $\ell$, could provide a double observational marker. In particular, while $\ell$ acts predominantly on the position of the critical point, in the barotropic fluid case, the electromagnetic contribution of $Q$ slightly dampens the inflow velocity near the horizon.