Conveners
Black Hole: Theory: Session 1
- Samir Mandal (Indian Institute of Space Science and Technology, Thiruvananthapuram, Kerala)
Black Hole: Theory: Session 2
- Indranil Chattopadhyay (ARIES, Nainital)
In the non-relativistic regime, fluid composition do not affect solution of equations of motion, until explicit cooling is considered. One of the main reason is that the information of composition is not included in the equation of state. We show that indeed composition affects solutions of accretion and jets around compact objects where the temperatures are transrelativistic. We also discuss...
We present the general relativistic magneto-hydrodynamic (GRMHD) accretion flow in Kerr space-time in the presence of the shock waves. Adopting the relativistic equation of state, we solve the governing equations in the ideal MHD limit and obtain the shock-induced GRMHD accretion solution for the first time to the best of our knowledge. We find that the subsonic flow entering from the outer...
Viscosity plays a vital role in accretion flows around black holes. It helps in the transport of angular momentum outwards allowing matter to get accreted into the potential well formed by the central compact object. Apart from angular momentum transport, viscosity also heats up the matter. In viscous transonic flows, both with and without shock solutions are possible. Many numerical...
We examine the effect of variable viscosity parameter ($\alpha$) in relativistic, low angular momentum advective accretion flow around rotating black holes. Following the recent simulation studies of magnetohydrodynamic disk that reveal the radial variation of $\alpha(r)$, we theoretically investigate the properties of the global transonic accretion flow considering a one-dimensional power law...
We study the relativistic, inviscid accretion flow in a generic stationary axisymmetric Kerr-Taub-NUT (KTN) space-time in presence of the shock waves. Along with the mass, this KTN space-time contains the spin parameter or the Kerr parameter ($a_{\rm k}$) and the NUT parameter ($n$). Depending on the values of $a_{\rm k}$ and $n$ this space-time represents either black-hole or naked...
Accretion is one of the ubiquitous mechanisms involved in astrophysics. Underlying model was developed from its simplistic spherical symmetric. form, namely Bondi accretion, in 1952, to the disk accretion with nonzero angular momentum in 1990s, to modern magnetically arrested accretion disk flow in the last decade. I will try to touch upon how with the improved and novel observations the...
The radiation pressure supported standard accretion disk model (Shakura Sunyaev 1973 model) is prone to classical thermal and viscous instabilities. However, these instabilities are not observed in astrophysical systems as disks remain thermally stable for astronomical time periods. In this talk, I will show some of the key findings of strongly magnetized accretion disks simulated using 3D...
Observations of X-ray binaries containing black holes indicate the presence of geometrically thick, hot, dynamic Compton cloud around the black hole to satisfactorily explain it’s spectral and temporal properties. In this work, I present results of a few high resolution, 3D hydrodynamic simulations of such Compton cloud around a non-rotating black hole. Our results demonstrate that the...
The central engine in active galactic nuclei (AGNs) and microquasars
is a black hole. As the black hole does not have any hard surface the jet must originate from the inner part of the accretion disc. The radiation field of the accretion disc interacts with the jet material as the jet travels through the radiation field. Various steady-state investigations have shown that the radiation field...
We study the relativistic, inviscid, advective accretion flow around the black holes and investigate a key feature of the accretion flow, namely the shock waves. We observe that the shock-induced accretion solutions are prevalent and such solutions are commonly obtained for a wide range of the flow parameters, such as energy (${\cal E}$) and angular momentum ($\lambda$), around the black holes...
