Estimation of bipolar jets from accretion discs around Kerr black holes

Abstract

We analyse flows around a rotating black hole and obtain self-consistent accretionejection 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 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 j∞ > 0.35c if Bernoulli parameter E 1.01 for a s > 0.99.

The 2D Disk Structure with Advective Transonic Inflow–Outflow Solutions around Black Holes

“…As the matter is moving inward, the flow variables are changed very fast and the flow becomes subsonic. This supersonic to subsonic transition of the inflow matter along the radial direction may give hint for the possibility of occurrence of shock transition in the flow, although this transition is not much sharp as accretion shocks studied in the literature (Fukue 1987;Chakrabarti 1989;Becker et al 2008;Lee et al 2016;Kumar & Chattopadhyay 2017). The outflows occurred close to the BH because the thermal pressure and rotation velocity are increasing very fast and the local energy (as the profile of B e in the Figure 1c, f and i) becomes sufficient to generate bipolar outflows.…”

“…Since the time scales of AGNs and BHXBs can be scaled by the mass of the BHs, but inner boundary conditions are same, so the basic physics of both kind of objects can be similar (McHardy et al 2006). In this context, there are a several theoretical and numerical studies on accretion processes with Keplerian/sub-Keplerian flows and that can play an important role in generations of soft spectrum (Shakura & Sunyaev 1973;Novikov & Thorne 1973;Abramowicz et al 1988) and hard spectral state (Sunyaev & Titarchuk 1980;Chakrabarti & Titarchuk 1995;Narayan & Yi 1995b;Esin et al 1997), hard/soft state transitions (Wu et al 2016), and the outflows from the accretion disks around BHs (Narayan & Yi 1995a;Molteni et al 1996a,b;Igumenshchev & Abramowicz 1999, 2000Ohsuga et al 2005;Okuda et al 2007;Yang et al 2014;Das et al 2014;Bu et al 2016a,b;Lee et al 2016;Kumar & Chattopadhyay 2017;Jiang et al 2017). The mechanism for the jet generation and evolution of it is still not much clear and a topic of active research in the fields of theory and observations.…”

Jet launching radius in low-power radio-loud AGNs in advection-dominated accretion flows

“…However, the jets launching radius will be larger, if GR or BH spin is taken into account. We speculate that when GR or BH spin is utilized, this would increase the accreted angular momentum due to frame-dragging (e.g., Kumar & Chattopadhyay 2017). As a result, this will force the centrifugal barrier to be at a larger orbit causing a shock radius or the jet launching radius to move further away from the event horizon.…”

“…Our value is about 500 larger, and this clearly implies that first-order Fermi acceleration process is very efficient in accelerating the high-energy particles to power the jets/outflows. Because our value is too large, this suggests that we need to relax our way of constraining the diffusion coefficient κ 0 in the transport equation as we have discussed above, or allowing the outflows to occur downstream from the shock location as suggested by Chakrabarti (1999), and more recently by Kumar & Chattopadhyay (2017). Additionally, the enhancement of emission from radiation due to the presence of a shock is expected to be about a factor of ∼ 5 − 6 comparing against the background gas when a shock is absent in the flow, and this is because we have shown that the mean energy of the relativistic particles in the disk is boosted by a factor of ∼ 5 − 6 at the shock location (e.g., LB05).…”

“…However, in actuality, the unbounded energies can be released in a range of distance below a shock location as we have suggested earlier. For example, Chakrabarti (1999) and Kumar & Chattopadhyay (2017) allowed the outflows to occur between the shock location and the inner sonic point. We speculate the huge energy dissipation fraction can be reduced by allowing the outflows to occur in the downstream region of the shock or over a small range of values in the vicinity of a shock (e.g., Lee & Becker 2017), since the particle acceleration process is strongest at the shock location.…”