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Indranil Chattopadhyay

Publications and source records attributed to Indranil Chattopadhyay.

61 records · Page 4Linked to original sources
arXiv2004

Computation of outflow rates from accretion disks around black holes

We self-consistently estimate the outflow rate from the accretion rates of an accretion disk around a black hole in which both the Keplerian and the sub-Keplerian matter flows simultaneously. While Keplerian matter supplies soft-photons, hot sub-Keplerian matter supplies thermal electrons. The temperature of the hot electrons is decided by the degree of inverse Comptonization of the soft photons. If we consider only thermally-driven flows from the centrifugal pressure-supported boundary layer around a black hole, we find that when the thermal electrons are cooled down, either because of the absence of the boundary layer (low compression ratio), or when the surface of the boundary layer is formed very far away, the outflow rate is negligible. For an intermediate size of this boundary layer the outflow rate is maximal. Since the temperature of the thermal electrons also decides the spectral state of a black hole, we predict that the outflow rate should be directly related to the spectral state.

astro-ph↗
arXiv2004

Radiatively driven electron-positron jets from two component accretion flows

Matter accreting onto black holes has long been known to have standing or oscillating shock waves. The post-shock matter puffs up in the form of a torus, which intercepts soft photons from the outer Keplerian disc and inverse Comptonizes to produce hard photons. The post-shock region also produces jets. We study the interaction of both hard photons and soft photons, with on-axis electron-positron jets. We show that the radiation from post-shock torus accelerates the flow to relativistic velocities, while that from the Keplerian disc has marginal effect. We also show that, the velocity at infinity or terminal velocity ${\vartheta}$, depends on the shock location in the disc.

astro-ph↗
arXiv2002

Radiatively Driven Plasma Jets around Compact Objects

Matter accreting onto black holes may develop shocks due to the centrifugal barrier. A part of inflowing matter in the post-shock flow is deflected along the axis in the form of jets. Post-shock flow which behaves like a Compton cloud has `hot' electrons emiting high energy photons. We study the effect of these `hot' photons on the outflowing matter. Radiation from this region could accelerate the outflowing matter but radiation pressure should also slow it down. We show that the radiation drag restricts the flow from attaining a very high velocity. We introduce the concept of an `equilibrium velocity' ($v_{eq} \sim 0.5c$) which sets the upper limit of the terminal velocity achieved by a cold plasma due to radiation deposition force in the absence of gravity. If the injection energy is $E_{in}$, then we find that the terminal velocity $v_\infty$ satisfies a relation $v_\infty^2 \lsim v_{eq}^2 + 2 E_{in}$.

astro-ph↗
arXiv2001

Standing Shocks around Black Holes: An Analytical Study

We compute locations of sonic points and standing shock waves in a thin, axisymmetric, adiabatic flow around a Schwarzschild black hole. We use completely analytical method to achieve our goal. Our results are compared with those obtained numerically and a good agreement is seen. Our results positively prove the existence of shocks in centrifugal pressure dominated flows. We indicate how our results could be used to obtain spectral properties and frequencies of shock oscillations which may be directly related to the quasi-periodic oscillations of hard X-rays.

astro-ph↗
arXiv2000

Bulk Motion Comptonization - a sure sign of Black Holes

Bulk motion Comptonization utilizes properties of both matter and radiation close to the horizon of a black hole. Computation with these considerations produce hard tails of energy spectral slope $\sim 1.5-1.7$. These are the most direct evidence of the horizon of a black hole. We argue that even in presence of winds and outflows this property is not likely to change as winds are negligible in soft states.

astro-ph↗
arXiv2000

On Radiative Acceleration of Jets and Outflows from Advective Disks

Jets and outflows are known to form out of advective accretion flows around black holes. Hard photons from the centrifugal barrier directly hit the electrons and deposit momentum on them. For optically thick flows such deposition is not efficient, but for optically thin flows matter could be accelerated to relativistic speed. In fact, even bound matter could be made free through successive deposition. We discuss these possibilities.

astro-ph↗