Estimation of bipolar jets from accretion discs around Kerr black holes

Abstract

We analyse flows around a rotating black hole and obtain self-consistent accretion-ejection solutions in full general relativistic prescription. Entire energy-angular momentum parameter space is investigated in the advective regime to obtain shocked and shock-free accretion solutions. Jet equations of motion are solved along the von-Zeipel surfaces computed from the post-shock disc, simultaneously with the equations of accretion disc along the equatorial plane. For a given spin parameter, the mass outflow rate increases as the shock moves closer to the black hole, but eventually decreases, maximizing at some intermediate value of shock location. Interestingly, we obtain all types of possible jet solutions, for example, steady shock solution with multiple critical points, bound solution with two critical points and smooth solution with single critical point. Multiple critical points may exist in jet solution for spin parameter $a_s\ge 0.5$. The jet terminal speed generally increases if the accretion shock forms closer to the horizon and is higher for corotating black hole than the counter-rotating and the non-rotating one. Quantitatively speaking, shocks in jet may form for spin parameter $a_s>0.6$ and jet shocks range between $6r_g$ and $130r_g$ above the equatorial plane, while the jet terminal speed $v_{{\rm j}\infty} > 0.35{\cm}$ if Bernoulli parameter ${\cal E}\geq1.01$ for $a_s>0.99$.