Low angular momentum relativistic hot accretion flow around Kerr black holes with variable adiabatic index

Abstract

We study the relativistic, time-independent, low angular momentum, inviscid, advective accretion flow around Kerr black hole. Considering the relativistic equation of state (REoS), we examine the transonic properties of the flow and find that there exists an upper bound of the location of the physically accepted critical point (r max out ). However, no such limit exists when an ideal gas equation of state (IEoS) is assumed to describe the flow. Further, we calculate the global accretion solutions that contain shock waves and separate the domain of parameter space in angular momentum (λ) and energy (E) plane. We find ample disagreement between the shock parameter spaces obtained for REoS and IEoS, respectively. In general, post-shock flow (equivalently post-shock corona, hereafter PSC) is characterized by shock location (r s ) and compression ratio (R, measure of density compression across the shock front) which are uniquely determined for flow with given input parameters, namely (E, λ). Using r s and R, we empirically compute the oscillation frequency (ν QP O ) of the shock front which is in general quasi-periodic (QP) in nature and retrace the domain of shock parameter space in the r s −R plane in terms of ν QP O for REoS around the weakly as well as rapidly rotating black holes. Finally, we indicate the relevance of the present work to explain the plausible origin of high frequency QPO (HFQPO) and its connection with the spin (a k ) of the Galactic black hole sources.

Effects of adiabatic index on the sonic surface and time variability of low angular momentum accretion flows

“…Nevertheless, our results stay in agreement with this work for their models with Ideal EoS (IEoS) and spinless black hole with a = 0. As it is shown in Dihingia et al (2019), for different values of , λ and spin parameter a, the range of compression ratio covers the values of (R) as R max = 3.79 down to R min = 1.19. From our simulation, we get a R max = 3.88 and R min = 1.3 for model D6 with γ = 1.4 during the whole evolution of the flow.…”

“…A more recent semi-analytic work shows the effects of variable adiabatic index on shock formation and oscillation by using a relativistic EoS (Dihingia et al 2019). We note that in our code we use the adiabatic EoS with a constant γ, due to the difficulties of the conservative MHD scheme embedded in HARM.…”

Shocks in relativistic viscous accretion flows around Kerr black holes

“…For GRO J1655−40, the source mass is estimated using the dynamical method as MBH = 5.1 − 6.3 M⊙ (Greene, Bailyn & Orosz 2001;Beer & Podsiadlowski 2002). Interestingly, contradictory claims appear in the measurement of the spin parameter (Abramowicz & Kluźniak 2001;Shafee et al 2006;Motta et al 2014;Aktar et al 2017;Dihingia, Das & Nandi 2019) which is yet to be settled. Hence, in this work, we consider 0.8 ≤ a k ≤ 0.99 for representation and calculate ν max QP O as before.…”

“…After the shock transition, flow momentarily slows down, however, gradually picks its radial velocity as it moves inward and ultimately enters into the black hole after crossing another critical point usually located close to the horizon. This renders the complete shock induced global accretion solution and solutions of this kind have been examined by several researchers (Fukue 1987;Chakrabarti 1989;Yang & Kafatos 1995;Lu, Gu & Yuan 1999;Becker & Kazanas 2001;Fukumura & Tsuruta 2004;Chakrabarti & Das 2004;Das 2007;Sarkar & Das 2016;Dihingia, Das & Mandal 2018a,b;Dihingia, Das & Nandi 2019). Due to shock compression, post-shock flow becomes hot and dense that results a puffed up torus like structure surrounding the black hole which is equivalently called as post-shock corona (hereafter PSC) (Aktar, Das & Nandi 2015).…”

Point-wise Self-similar Solution for Spiral Shocks in Accretion Disk with Mass Outflow in Binary

“…As a useful supplement to prevailing theory, the shocks in accretion flow, including the axisymmetric radially standing shocks and non-axisymmetric spiral shocks, have been rigorously investigated in literature over past decades. Series of theoretical works proposed and gradually improved the radially standing shock model Corresponding author: Ramiz Aktar & Li Xue ramizaktar@gmail.com, lixue@xmu.edu.cn (Fukue 1987;Chakrabarti 1989;Lu et al 1999;Becker & Kazanas 2001;Fukumura & Tsuruta 2004;Chakrabarti & Das 2004;Sarkar & Das 2016;Sarkar et al 2018;Dihingia et al 2018Dihingia et al , 2019b. This model has been used to explain the observational spectral states and quasiperiodic oscillations of compact objects (Chakrabarti & Titarchuk 1995;Molteni et al 1996).…”