Estimation of the mass outflow rates from viscous accretion discs

Kumar, Rajiv; Chattopadhyay, Indranil

doi:10.1093/mnras/sts641

Cited by 46 publications

(60 citation statements)

References 57 publications

(87 reference statements)

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“…Here, we consider two different values of adiabatic index that represents accretion flow lying in the range between ultra-relativistic (γ = 4/3) to semi-non-relativistic (γ = 1.5) domain. We observe that in all cases, α cri B initially increases with βin and asymptotically approaches to the saturation values ∼ 0.4 (for γ = 4/3) and ∼ 0.27 (for γ = 1.5), respectively for gas pressure dominated flow Chakrabarti & Das (2004); King et al (2007); Das et al (2009) ;Kumar & Chattopadhyay (2013). Our steady model eventually establishes the fact that global shocks accretion solution can be obtained for fairly high viscosity parameter (Fig.…”

Section: Discussionsupporting

confidence: 75%

“…In this analysis, we treat f as a free parameter and chose its value as f = 0.998 for representation. Evidently, this is the measure of energy dissipation across the shock (Das et al 2010;Singh & Chakrabarti 2011;Sarkar & Das 2013;Kumar & Chattopadhyay 2013). We then compute the maximum energy dissipation (∆E max ) by freely varying all the flow parameters and plot it as function of βin for various values of accretion rates in Fig.…”

Section: Global Accretion Solutionsmentioning

confidence: 99%

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Properties of magnetically supported dissipative accretion flow around black holes with cooling effects

Sarkar

Das

Mandal

2017

Monthly Notices of the Royal Astronomical Society

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We investigate the global structure of the advection dominated accretion flow around a Schwarzschild black hole where the accretion disc is threaded by toroidal magnetic fields. We consider synchrotron radiative process as an effective cooling mechanism active in the flow. With this, we obtain the global transonic accretion solutions by exploring the variety of boundary conditions and dissipation parameters, namely accretion rate (ṁ) and viscosity (α B ). The fact that depending on the initial parameters, steady state accretion flows can possess centrifugally supported shock waves. These global shock solutions exist even when the level of dissipation is relatively high. We study the properties of shock waves and observe that the dynamics of the post-shock corona (hereafter, PSC) is regulated by the flow parameters. Interestingly, we find that shock solution disappears completely when the dissipation parameters exceed their critical values. We calculate the critical values of viscosity parameter (α cri B ) adopting the canonical values of adiabatic indices as γ = 4/3 (ultra-relativistic) and 1.5 (seminon-relativistic) and find that in the gas pressure dominated domain, α cri B ∼ 0.4 for γ = 4/3 and α cri B ∼ 0.27 for γ = 1.5, respectively. We further show that global shock solutions are relatively more luminous compared to the shock free solutions. Also, we have calculated the synchrotron spectra for shocked solutions. When the shock is considered to be dissipative in nature, it would have an important implication as the available energy at PSC can be utilized to power the outflowing matter escaped from PSC. Towards this, we calculate the maximum shock luminosity and discuss the observational implication of our present formalism.

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Section: Discussionsupporting

confidence: 75%

Section: Global Accretion Solutionsmentioning

confidence: 99%

Properties of magnetically supported dissipative accretion flow around black holes with cooling effects

Sarkar

Das

Mandal

2017

Monthly Notices of the Royal Astronomical Society

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“…In passing, we may mention that our result differs significantly from an earlier work 13 in that we maintain continuity of angular momentum across an axisymmetric shock by choosing an appropriate stress condition. This led to a change in limits of the viscosity parameter.…”

Section: Conclusion and Discussioncontrasting

confidence: 59%

Thermal dissipation and outflows originating at shock front in viscous accretion flow around a black hole

Nagarkoti¹,

Chakrabarti²

2017

The Fourteenth Marcel Grossmann Meeting

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We use α prescription of viscosity and study steady state solutions of an accretion flow, in presence of dissipative shocks. The flow solutions depend on four initial parameters namely, E in , l H , α and f . We study all such solutions possible and divide the parameter space into regions which allow the formation of such shock waves and which do not. Then, we follow a similar study in presence of outflows. From the analysis of the resultant parameter space, we find that the dissipative shocks can still form for the values of α as high as 0.27 in small regions of the flow parameter space in absence of outflows. This value reduces to 0.2 in presence of outflows. The typical values of α appear in the range 0.01 − 0.15. The values of α reported from numerical simulations are always lower than 0.1. This signifies that viscosity parameter in accretion flows is low enough to form dissipative shocks, both in presence and absence of outflows. This supports our claim that shocks could be omnipresent. It was also found that a dissipation factor of f > 0.3 does not produce shocks in significant region of the flow parameter space and hence, these values are not physically relevant. Likewise, at the maximum, ∼ 13% of inflowing matter can be ejected as outflows at the CENBOL.

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“…In the present paper we include these after combining the description of the outflow, and formalism of dissipation as present in the literature (Das & Chakrabarti 1999;Singh & Chakrabarti 2012;Kumar & Chattopadhyay 2013). In Kumar & Chattopadhyay (2013) dΩ dx was chosen to be continuous which triggers a jump in the angular momentum at the shock, while we use a continuity in angular momentum since we are discussing axisymmetric shocks. This difference induces major changes in the Rankine-Hugoniot conditions, though, some of their conclusions remain similar to those present in our work.…”

Section: Discussionmentioning

confidence: 99%

“…If these estimates are lower as compared to our limits, it would indicate that CENBOL would form and radiation emitted from it is an integral part of the c 2016 The Authors spectral and timing properties of black holes. It has been shown recently (Nagarkoti & Chakrabarti (2016) [Paper I]; see also, Kumar & Chattopadhyay (2013), with a different viscous stress prescription), that there is an upper limit on the Shakura & Sunyaev (1973) viscosity parameter above which three sonic points and therefore standing shocks are not possible in a viscous accretion flow. These results were predicted by Chakrabarti (1990a) and Chakrabarti (1996a) in the context of isothemal and polytropic flows respectively where it was shown that the topology of solutions change dramatically beyond a critical value of viscosity.…”

Section: Introductionmentioning

confidence: 99%

Viscosity parameter in dissipative accretion flows with mass outflow around black holes

Nagarkoti

Chakrabarti

2016

Mon. Not. R. Astron. Soc.

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Numerical hydrodynamic simulation of inviscid and viscous flows have shown that significant outflows could be produced from the CENtrifugal pressure supported BOundary Layer or CENBOL of an advective disk. However, this barrier is weakened in presence of viscosity, more so, if there are explicit energy dissipations at the boundary layer itself. We study effects of viscosity and energy dissipation theoretically on the outflow rate and show that as the viscosity or energy dissipation (or both) rises, the prospect of formation of outflows is greatly reduced, thereby verifying results obtained through observations and numerical simulations. Indeed, we find that in a dissipative viscous flow, shocks in presence of outflows can be produced only if the Shakura-Sunyaev viscosity parameter α is less than 0.2. This is a direct consequence of modification of the Rankine-Hugoniot relation across the shock in a viscous flow, when the energy dissipation and mass loss in the form of outflows from the post-shock region are included. If we ignore the effects of mass loss altogether, the standing dissipative shocks in viscous flows may occur only if α < 0.27. These limits are tighter than the absolute limit of α = 0.3 valid for a situation when the shock itself neither dissipates energy nor any outflow is formed. We compute typical viscosity parameters required to understand spectral and temporal properties of several black hole candidates such as GX399-4, MAXI J1659-152 and MAXI J1836-194 and find that required α are indeed well within our prescribed limit.

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Estimation of the mass outflow rates from viscous accretion discs

Cited by 46 publications

References 57 publications

Properties of magnetically supported dissipative accretion flow around black holes with cooling effects

Properties of magnetically supported dissipative accretion flow around black holes with cooling effects

Thermal dissipation and outflows originating at shock front in viscous accretion flow around a black hole

Viscosity parameter in dissipative accretion flows with mass outflow around black holes

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