Dissipative accretion flows around a rotating black hole

J. Cosmol. Astropart. Phys.

2022

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We present the global solutions of low angular momentum, inviscid, advective accretion flow around Kerr-Taub-NUT (KTN) black hole in presence and absence of shock waves. These solutions are obtained by solving the governing equations that describe the relativistic accretion flow in KTN spacetime which is characterized by the Kerr parameter (a k) and NUT parameter (n). During accretion, rotating flow experiences centrifugal barrier that eventually triggers the discontinuous shock transition provided the relativistic shock conditions are satisfied. In reality, the viability of shocked accretion solution appears more generic over the shock free solution as the former possesses high entropy content at the inner edge of the disc. Due to shock compression, the post-shock flow (equivalently post-shock corona, hereafter PSC) becomes hot and dense, and therefore, can produce high energy radiations after reprocessing the soft photons from the pre-shock flow via inverse Comptonization. In general, PSC is characterized by the shock properties, namely shock location (rs ), compression ratio (R) and shock strength (S), and we examine their dependencies on the energy (ξ) and angular momentum (λ) of the flow as well as black hole parameters. We identify the effective domain of the parameter space in λ-ξ plane for shock and observe that shock continues to form for wide range of flow parameters. We also find that a k and n act oppositely in determining the shock properties and shock parameter space. Finally, we calculate the disc luminosity (L) considering free-free emissions and observe that accretion flows containing shocks are more luminous compared to the shock free solutions.

Section: Parameter-space For Shockmentioning

confidence: 89%

Section: Shock Propertiesmentioning

confidence: 94%

Study of relativistic accretion flow around KTN black hole with shocks

Sen

Maity

J. Cosmol. Astropart. Phys.

2022

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“…This causes the piling of matter which eventually may trigger the shock transition. The feasibility of shock solutions and its implications have been studied extensively around non-rotating black holes (Fukue 1987;Chakrabarti 1989;Lu et al 1999;Becker & Kazanas 2001;Das et al 2001a;Fukumura & Tsuruta 2004;Chakrabarti & Das 2004;Das 2007;Das et al 2009;Sarkar & Das 2016) as well as rotating black holes (Chakrabarti 1996b;Das & Chakrabarti 2008;Das et al 2010;Aktar et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Estimation of mass outflow rates from dissipative accretion disc around rotating black holes

Aktar

Monthly Notices of the Royal Astronomical Society

Nandi

et al. 2017

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We study the properties of the dissipative accretion flow around rotating black holes in presence of mass loss. We obtain the complete set of global inflow-outflow solutions in the steady state by solving the underlying conservation equations selfconsistently. We observe that global inflow-outflow solutions are not the isolated solution, instead such solutions are possible for wide range of inflow parameters. Accordingly, we identify the boundary of the parameter space for outflows, spanned by the angular momentum (λ in ) and the energy (E in ) at the inner sonic point (x in ), as function of the dissipation parameters and find that parameter space gradually shrinks with the increase of dissipation rates. Further, we examine the properties of the outflow rate Rṁ (defined as the ratio of outflow to inflow mass flux) and ascertain that dissipative processes play the decisive role in determining the outflow rates. We calculate the limits on the maximum outflow rate (R maẋ m ) in terms of viscosity parameter (α) as well as black hole spin (a k ) and obtain the limiting range as 3% R maẋ m 19%. Moreover, we calculate the viable range of α that admits the coupled inflow-outflow solutions and find that α 0.25 for Rṁ = 0. Finally, we discuss the observational implication of our formalism to infer the spin of the black holes. Towards this, considering the highest observed QPO frequency of black hole source GRO J1655-40 (∼ 450 Hz), we constrain the spin value of the source as a k 0.57.

“…It is generally believed that in the context of understanding the black hole spectral properties (Chakrabarti & Mandal 2006) as well as jets and outflows (Das & Chakrabarti 2008;Aktar et al 2015;Sarkar & Das 2016;Aktar et al 2017), shock induced global accretion solutions are potentially preferred over the shock free solutions. Therefore, it is worthy to identify the range of flow parameters that admits shocks.…”

Section: Global Accretion Solutions Including Shockmentioning

confidence: 99%

Accretion-ejection in rotating black holes: a model for ‘outliers’ track of radio-X-ray correlation in X-ray binaries

Aktar

Nandi

2019

Astrophys Space Sci

Self Cite

We study the global accretion-ejection solutions around a rotating black hole considering three widely accepted pseudo-Kerr potentials that satisfactorily mimic the space-time geometry of rotating black holes. We find that all the pseudo potentials provide standing shock solutions for large range of flow parameters. We identify the effective region of the shock parameter space spanned by energy (E in ) and angular momentum (λ in ) measured at the inner critical point (x in ) and find that the possibility of shock formation becomes feeble when the viscosity parameter (α) is increased. In addition, we find that shock parameter space also depends on the adiabatic index (γ) of the flow and the shock formation continues to take place for a wide range of γ as 1.5 ≤ γ ≤ 4/3. For all the pseudo potentials, we calculate the critical viscosity parameter (α cri shock ) beyond which standing shock ceases to exist and compare them as function of black hole spin (a k ). We observe that all the pseudo potentials under consideration are qualitatively similar as far as the standing shocks are concerned, however, they differ both qualitatively and quantitatively from each other for rapidly rotating black holes. Further, we compute the mass loss from the disc using all three pseudo potentials and find that the maximum mass outflow rate (R maẋ m ) weakly depends on the black hole spin. To validate our model, we calculate the maximum jet kinetic power using the accretion-ejection formalism and compare it with the radio jet power of low-hard state of the black hole X-ray binaries (hereafter XRBs). The outcome of our results indicate that XRBs along the 'outliers' track might be rapidly rotating.