Choked accretion onto Kerr-Sen black holes in Einstein-Maxwell-dilaton-axion gravity

TL;DR

This paper models ultrarelativistic fluid accretion onto Kerr-Sen black holes within Einstein-Maxwell-dilaton-axion gravity, revealing how dilaton parameters influence flow dynamics and radiative efficiency.

Contribution

It provides new analytical solutions for fluid flow and flow parameters around Kerr-Sen black holes, highlighting the effects of dilaton fields on accretion processes.

Findings

Ejection rate to injection rate ratio increases with dilaton parameter.

Radiative efficiency is higher for Kerr-Sen black holes than Kerr black holes.

Redshift decreases as dilaton parameter increases.

Abstract

We investigate the process of an ultrarelativistic fluid accreted onto axisymmetric Kerr-Sen black holes in Einstein-Maxwell-dilaton-axion theory. We obtain the solution describing the velocity potential of a stationary irrotational fluid with a stiff equation of state and the solution for the streamlined diagram of the quadrupolar flow. We also investigate how the solution's coefficients and the stagnation points are affected by the parameters. The injection rate, the ejection rate, and the critical angle are discussed in detail. We find that with an increasing dilaton parameter the ratio of the ejection rate to the injection rate increases and that the radiative efficiency is larger, while the redshift is lower, compared to the Kerr black hole.