On the possibilities of mass loss from an advective accretion disc around stationary black holes (original) (raw)
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Mass-loss from advective accretion disc around rotating black holes
Monthly Notices of the Royal Astronomical Society, 2015
We examine the properties of the outflowing matter from an advective accretion disc around a spinning black hole. During accretion, rotating matter experiences centrifugal pressure supported shock transition that effectively produces a virtual barrier around the black hole in the form of post-shock corona (hereafter, PSC). Due to shock compression, PSC becomes hot and dense that eventually deflects a part of the inflowing matter as bipolar outflows because of the presence of extra thermal gradient force. In our approach, we study the outflow properties in terms of the inflow parameters, namely specific energy (E) and specific angular momentum (λ) considering the realistic outflow geometry around the rotating black holes. We find that spin of the black hole (a k) plays an important role in deciding the outflow rate Rṁ (ratio of mass flux of outflow and inflow), in particular, Rṁ is directly correlated with a k for the same set of inflow parameters. It is found that a large range of the inflow parameters allows global accretion-ejection solutions and the effective area of the parameter space (E, λ) with and without outflow decreases with black hole spin (a k). We compute the maximum outflow rate (R maẋ m) as function of black hole spin (a k) and observe that R maẋ m weakly depends on a k that lies in the range ∼ 10% − 18% of the inflow rate for the adiabatic index (γ) with 1.5 γ 4/3. We present the observational implication of our approach while studying the steady/persistent Jet activities based on the accretion states of black holes. We discuss that our formalism seems to have the potential to explain the observed Jet kinetic power for several Galactic Black Hole sources (GBHs) and Active Galactic Nuclei (AGNs).
Accretion-ejection mechanism from advective accretion disc around rotating black holes
2018
Powerful jets and outflows are commonly observed in accreting black hole systems including active galactic nuclei (AGNs) and X-ray binaries (XRBs). In spite of the rigorous investigations carried out in both theoretical as well as observational fronts, the physical mechanism of jet generation and its powering processes are still remain elusive. In this context, the earlier theoretical investigations predicted that the powering of jets may be due to the spin of the black holes. However, the contradictory claims have been made in the observational front. Motivating with this, we investigate the effect of spin on mass loss from the accretion disc around rotating black holes. In the first work, we investigate the effect of spin on the mass outflow rates from a steady, advective, inviscid, geometrically thin accretion flow around a rotating black hole. For this purpose, we adopt pseudo-Kerr potentials to mimic the spacetime geometry around rotating black holes. We observe that the accret...
Dissipative advective accretion disc solutions with variable adiabatic index around black holes
We investigated accretion on to black holes in presence of viscosity and cooling, by employing an equation of state with variable adiabatic index and multi-species fluid. We obtained the expression of generalized Bernoulli parameter which is a constant of motion for an accretion flow in presence of viscosity and cooling. We obtained all possible transonic solutions for a variety of boundary conditions, viscosity parameters and accretion rates. We identified the solutions with their positions in the parameter space of generalized Bernoulli parameter and the angular momentum on the horizon. We showed that a shocked solution is more luminous than a shock-free one. For particular energies and viscosity parameters, we obtained accretion disc luminosities in the range of 10 −4 − 1.2 times Eddington limit, and the radiative efficiency seemed to increase with the mass accretion rate too. We found steady state shock solutions even for high-viscosity parameters, high accretion rates, and for wide range of composition of the flow, starting from purely electronproton to lepton-dominated accretion flow. However, similar to earlier studies of inviscid flow, accretion shock was not obtained for electron-positron pair plasma.
Computation of mass loss from viscous accretion disc in presence of cooling
New Astronomy, 2008
Rotating accretion flow may undergo centrifugal pressure mediated shock transition even in presence of various dissipative processes, such as viscosity and cooling mechanism. The extra thermal gradient force along the vertical direction in the post-shock flow drives a part of the accreting matter as bipolar outflows which are believed to be the precursor of relativistic jets. We compute mass loss rates from a viscous accretion disc in presence of synchrotron cooling in terms of the inflow parameters. We show cooling significantly affects the mass outflow rate, to the extent that, jets may be generated from flows with higher viscosity. We discuss that our formalism may be employed to explain observed jet power for a couple of black hole candidates. We also indicate that using our formalism, it is possible to connect the spectral properties of the disc with the rate of mass loss.
Relativistic outflows from advection-dominated accretion disks around black holes
Astrophysical Journal - ASTROPHYS J, 2001
Advection-dominated accretion flows (ADAFs) have a positive Bernoulli parameter and are therefore gravitationally unbound. The Newtonian ADAF model has been generalized recently to obtain the ADIOS model that includes outflows of energy and angular momentum, thereby allowing accretion to proceed self-consistently. However, the utilization of a Newtonian gravitational potential limits the ability of this model to describe the inner region of the disk, where any relativistic outflows are likely to originate. In this paper we modify the ADIOS scenario to incorporate a pseudo-Newtonian potential, which approximates the effects of general relativity. The analysis yields a unique, self-similar solution for the structure of the coupled disk/wind system. Interesting features of the new solution include the relativistic character of the outflow in the vicinity of the radius of marginal stability, which represents the inner edge of the quasi-Keplerian disk in our model. Hence, our self-simila...
Monthly Notices of the Royal Astronomical Society, 2013
Using long-duration general relativistic magnetohydrodynamic simulations of radiatively inefficient accretion discs, the energy, momentum and mass outflow rates from such systems are estimated. Outflows occur via two fairly distinct modes: a relativistic jet and a subrelativistic wind. The jet power depends strongly on the black hole spin and on the magnetic flux at the horizon. Unless these are very small, the energy output in the jet dominates over that in the wind. For a rapidly spinning black hole accreting in the magnetically arrested limit, it is confirmed that jet power exceeds the total rate of accretion of rest mass energy. However, because of strong collimation, the jet probably does not have a significant feedback effect on its immediate surroundings. The power in the wind is more modest and shows a weaker dependence on black hole spin and magnetic flux. Nevertheless, because the wind subtends a large solid angle, it is expected to provide efficient feedback on a wide range of scales inside the host galaxy. Empirical formulae are obtained for the energy and momentum outflow rates in the jet and the wind.
Estimation of the mass outflow rates from viscous accretion discs
Monthly Notices of the Royal Astronomical Society, 2013
We study the viscous accretion disc around black holes, and all possible accretion solutions, including shocked as well as shock-free accretion branches. Shock-driven bipolar outflows from a viscous accretion disc around a black hole have been investigated. One can identify two critical viscosity parameters, α cl and α cu , within which the stationary shocks may occur, for each set of boundary conditions. Adiabatic shock has been found for up to viscosity parameter α = 0.3, while in the presence of dissipation and mass loss we have found stationary shock up to α = 0.15. The mass outflow rate may increase or decrease with the change in disc parameters, and is usually around a few to 10 per cent of the mass inflow rate. We show that for the same outer boundary condition, the shock front decreases to a smaller distance with the increase in α. We also show that the increase in dissipation reduces the thermal driving in the post-shock disc, and hence the mass outflow rate decreases up to a few per cent.
Effect of the flow composition on outflow rates from accretion discs around black holes
We studied the outflow behaviour from accretion discs around black holes taking into account the vertical equilibrium accretion flow model. The outflow rate is found to depend crucially on flow composition. Our approach is to study the outflow behaviour as function of inflow around black holes with an equation of state which allows flow to be thermally relativistic close to black holes and non-relativistic far away from black holes. We studied shock ejection model. A pure electron–positron pair flow never undergoes shock transition while presence of some baryons (common in outflows and jets) makes it possible to have standing shock waves in the flow. It can be concluded that the presence of protons is necessary for the flow to show the outflow behaviour. The outflow rate is maximum when the flow contains the proton number density which is 27 per cent of the electron number density. We conclude that a pure electron–positron jet is unlikely to form.
Behaviour of dissipative accretion flows around black holes
Monthly Notices of The Royal Astronomical Society, 2007
We investigate the behaviour of dissipative accreting matter close to a black hole, as this provides important observational features of galactic and extragalactic black hole candidates. We find a complete set of global solutions in the presence of viscosity and synchrotron cooling. We show that advective accretion flow can have a standing shock wave and the dynamics of the shock is controlled by the dissipation parameters (both viscosity and cooling). We study the effective region of the parameter space for standing as well as oscillating shock. We find that the shock front always moves towards the black hole as the dissipation parameters are increased. However, viscosity and cooling have opposite effects in deciding the solution topologies. We obtain two critical cooling parameters that separate the nature of the accretion solution.