# Bondi Accretion in the Spherically Symmetric Johannsen-Psaltis Spacetime

## TL;DR

This paper investigates how scalar hair deviations in the Johannsen-Psaltis spacetime affect gas accretion rates and particle dynamics, extending classical accretion models to modified black hole metrics.

## Contribution

It introduces a generalized pseudo-Newtonian potential and analyzes accretion in the Johannsen-Psaltis spacetime, highlighting the impact of scalar hair on accretion and gravity.

## Key findings

- Scalar hair parameter $\\epsilon_{3}$ influences accretion rates.
- Positive $\\epsilon_{3}$ reduces accretion and gravity.
- Negative $\\epsilon_{3}$ enhances accretion and gravity.

## Abstract

The Johannsen-Psaltis spacetime explicitly violates the no hair theorem. It describes rotating black holes with scalar hair in the form of parametric deviations from the Kerr metric. In principle, black hole solutions in any modified theory of gravity could be written in terms of the Johannsen-Psaltis metric. We study the accretion of gas onto a static limit of this spacetime. We utilise a recently proposed pseudo-Newtonian formulation of the dynamics around arbitrary static, spherically symmetric spacetimes. We obtain a potential that generalises the Paczy\'nski-Wiita potential to the static Johannsen-Psaltis metric. We also perform a fully relativistic analysis of the geodesic equations in the static Johannsen-Psaltis spacetime. We find that positive values of the scalar hair parameter, $\epsilon_{3}$, lower the accretion rate and vice versa. Similarly, positive (negative) values of $\epsilon_{3}$ reduce (increase) the gravitational acceleration of radially infalling massive particles.