Radiatively driven relativistic jets with variable adiabatic index equation of state

TL;DR

This study models relativistic jets driven by radiation from accretion discs around black holes, highlighting how accretion rates, flow composition, and black hole mass influence jet speeds, with implications for understanding ultra-relativistic jets.

Contribution

It introduces a detailed relativistic model of radiatively driven jets with variable adiabatic index, accounting for special relativistic effects and black hole mass differences.

Findings

Jet terminal speed increases with accretion rates and synchrotron emission.

Jets around supermassive black holes can become ultra-relativistic at high accretion rates.

Stellar mass black hole jets achieve Lorentz factors around 10.

Abstract

We investigate a relativistic fluid jet driven by radiation from a shocked accretion disc around a non-rotating black hole approximated by Paczy\'nski-Wiita potential. The sub-Keplerian and Keplerian accretion rates control the shock location and therefore, the radiation field around the accretion disc. We compute the radiative moments with full special relativistic transformation. The effect of a fraction of radiation absorbed by the black hole has been approximated, over and above the special relativistic transformations. We show that the radiative moments around a super massive black hole are different compared to that around a stellar mass black hole. We show that the terminal speed of jets increases with the mass accretion rates,synchrotron emission of the accretion disc and reduction of proton fraction of the flow composition. To obtain relativistic terminal velocities of jets, both thermal and radiative driving are important. We show for very high accretion rates and pair dominated flow, jets around super massive black holes are truly ultra-relativistic, while for jets around stellar mass black holes, terminal Lorentz factor of about $10$ is achievable.