MG15 - Talk detail

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Session

Accepted

Yes

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Time

Talk

Title

Abstract

The outward transport of the angular momentum of accreting matter leads to the accretion flow and formation of disc around the compact objects. Here, we discuss the importance of large scale strong magnetic field in the removal of angular momentum outward, as well as the possible origin of different kinds of magnetic barrier in advective, geometrically thick, sub-Keplerian accretion flows around black holes. The origin of this large scale strong magnetic field near the event horizon is due to the advection of the magnetic flux by the accreting gas from the environment, say, the interstellar medium or a companion star, because of flux freezing. In this simplest vertically averaged, 1.5-dimensional disc model, we choose the maximum upper limit of the magnetic field, which the disc around a black hole can sustain. In this circumstance, the accreting gas either decelerates or faces the magnetic barrier near the event horizon by the accumulated magnetic field depending on the geometry. We suggest that these types of flow are the basic building block to produce jets and outflows in the accreting system. We also find that in some cases, when matter is trying to go back to infinity after knocking the barrier, it is prevented being escaped by the cumulative action of strong gravity and the magnetic tension, hence by another barrier. In this way, magnetic field can lock the matter in between these two barriers and it might be a possible explanation for the formation of episodic jet.

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Session

Accepted

Yes

Order

Time

Talk

Title

Abstract

The most self-consistent approach, in order to understand vertical transport of matter through the magnetic effects, which in turn leads to the radial in-fall of the rest of the matter, is considering the flow to be moving in the vertical direction from the disc plane. Such an attempt, in the absence of magnetic effects, was made earlier by Bhattacharya, Ghosh & Mukhopadhyay (2010) in the model framework of coupled disc-outflow systems. In such a framework, we can see the energetics of the disc outflow strongly depend on the mass, accretion rate, and spin of the black holes. Here, we explore the coupled 2.5-dimensional disc-outflow systems in the presence of large-scale magnetic field enabling angular momentum transport, when the magnetic field plays an indispensable role in order to generate vertical flux in the three-dimensional flows. We attempt to reproduce the observed luminosities (L) of two extreme cases - the under-fed AGNs and quasars (e.g. Sgr A*) with L ~ 10^33 ergs/sec to ultra-luminous X-ray sources with L ~ 10^40 ergs/sec, at different combinations of mass accretion rate, ratio of specific heats, magnetic field geometry and Kerr parameter.

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