Sandip K. Chakrabarti
Articles written in Journal of Astrophysics and Astronomy
Volume 9 Issue 1 March 1988 pp 49-61
Spacetime with self-gravitating thick disc
We compute the metric coefficients and study some properties of the spacetime comprising of a Schwarzschild hole distorted by a self gravitating thick disc.
Volume 9 Issue 4 December 1988 pp 185-192
Vortex rings in the working surface of radio jets
We study the effects of the presence of vortex rings surrounding a supersonic radio jet inside the cocoon of a radio lobe. We show that both the jet and the shocked ambient medium are pinched. Flow speed inside the cocoon is always close to the sonic value and it stays so by successively passing through several oblique shocks. We also discuss the possibility of the non-linear growth of the instabilities of the contact surface to explain the numerical results in the literature.
Volume 9 Issue 4 December 1988 pp 243-248
On the damping of the bending waves in Saturn’s ring
We study numerically the motion of a single particle in the bending wave of finite thickness in Saturn’s ring. We include the forcing due to the planet, a moon, the coriolis force and the self gravity of the ring. In particular, we compute the variation of the velocity arising due to the variation of the amplitude and the phase of the epicyclic motion across the local vertical height of the ring. We suggest that the dissipation of energy due to the collision of ring particles in this shear layer damps out the bending wave of Saturn’s ring at the 5:3 vertical resonance of Mimas within a distance of 150 km from the site of its launching as is observed in Voyager data.
Volume 10 Issue 3 September 1989 pp 261-277
Multiple shocks in the rotating winds from self-gravitating discs
We present the analytic theory of dissipative and non-dissi-pative shocks in the rotating outflows in both the pseudo-Newtonian and the Schwarzschild geometry. We include the effects of the self gravity of the surrounding massive disc and show that the flow may have as many as five critical points when the angular momentum and the disc mass are sufficiently high. This leads to the possibility of the multiple
Volume 11 Issue 1 March 1990 pp 29-35
The Newtonian forces in the Kerr geometry
Sandip K. Chakrabarti A. R. Prasanna
We study the properties of the ’Newtonian forces’ acting on a test particle in the field of the Kerr black hole geometry. We show that the centrifugal force and the Coriolis force reverse signs at several different locations. We point out the possible relevance of such reversals particularly in the study of the stability properties of the compact rotating stars and the accretion discs in hydrostatic equilibria
Volume 23 Issue 1-2 March 2002 pp 143-147
Standing shocks around black holes and estimation of outflow rates
Santabrata Das Sandip K. Chakrabarti
We self-consistently obtain shock locations in an accretion flow by using an analytical method. One can obtain the spectral properties, quasi-periodic oscillation frequencies and the outflow rates when the inflow parameters are known. Since temperature of the CENBOL decides the spectral states of the black hole, and also the outflow rate, the outflow rate is directly related to the spectral states.
Volume 23 Issue 1-2 March 2002 pp 149-153
Radiatively driven winds from effective boundary layer around black holes
Indranil Chattopadhyay Sandip K. Chakrabarti
Matter accreting onto black holes suffers a standing or oscillating shock wave in much of the parameter space. The post-shock region is hot, puffed up and reprocesses soft photons from a Keplerian disc to produce the characteristic hard tail of the spectrum of accretion discs. The post-shock torus is also the base of the bipolar jets. We study the interaction of these jets with the hard photons emitted from the disc. We show that radiative force can accelerate outflows but the drag can limit the terminal speed. We introduce an equilibrium speed υ_{eq} as a function of distance, above which the flow will experience radiative deceleration.
Volume 23 Issue 1-2 March 2002 pp 155-164
Interaction of accretion shocks with winds
Kinsuk Acharya Sandip K. Chakrabarti D. Molteni
Accretion shocks are known to oscillate in presence of cooling processes in the disk. This oscillation may also cause quasi-periodic oscillations of black holes. In the presence of strong winds, these shocks have oscillations in vertical direction as well. We show examples of shock oscillations under the influence of both the effects. When the shocks are absent and the flow is cooler, the wind becomes weaker and the vertical oscillation becomes negligible.
Volume 23 Issue 3-4 December 2002 pp 213-233
S. Naik A. R. Rao Sandip K. Chakrabarti
We present the results of a detailed analysis of RXTE observations of class
Volume 43 All articles Published: 3 December 2022 Article ID 0090
Study of accretion flows around an ultraluminous X-ray source M82 X-1 using NuSTAR data
SANTANU MONDAL BISWARAJ PALIT SANDIP K. CHAKRABARTI
We study the spectral properties and accretion flow behavior of an ultraluminous X-ray source M82X-1 using NuSTAR observations. We use the physical two-component advective flow (TCAF) model to fit the data and to derive the accretion flow properties of the source. From the model fitted parameters, we found that M82X-1 is harboring an intermediate mass black hole at its centre, where the mass varies from$156.04^{+13.51}_{-15.30}$ to $380.96^{+28.38}_{-29.76}$ $M_{\odot}$. The error weighed average mass of the black hole is $273 \pm 43$ $M_{\odot}$, whichaccreted in nearly super-Eddington rate. The Compton cloud was compact with a size of $\sim$13$r_g$ and the shock compression ratio had nearly intermediate values except for the epoch four. These indicate a possible significant mass outflow from the inner region of the disk. The quasi periodic oscillation (QPO) frequencies estimatedfrom the model fitted parameters can reproduce the observed QPOs. The robustness of the model parameters is verified by drawing the confidence contours among them.
Volume 44, 2023
All articles
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