67 research outputs found
Properties of accretion shock waves in viscous flows with cooling effects
We study the properties of the shock waves for a viscous accretion flow
having low angular momentum in presence of synchrotron cooling. We present all
possible accretion solutions in terms of flow parameters. We identify the
region of the parameter space for steady and oscillating shocks and show the
effect of various energy dissipation processes on it. We discuss the role of
the shock waves while explaining the observations from black hole candidates.Comment: 3 pages; 3 figures; prepared on the basis of the talk presented in
the MG11 Meeting on General Relativity, Berlin, July 23-29, 200
Parameter space study of magnetohydrodynamic flows around magnetized compact objects
We solve the magnetohydrodynamic (MHD) equations governing axisymmetric flows
around neutron stars and black holes and found all possible solution topologies
for adiabatic accretion. We divide the parameter space spanned by the conserved
energy and angular momentum of the flow in terms of the flow topologies. We
also study the possibility of the formation of the MHD shock waves.Comment: 3 pages; 4 figures; prepared on the basis of the talk presented in
the MG11 Meeting on General Relativity, Berlin, July 23-29, 200
Study of mass outflow rates from magnetized advective accretion disk around rotating black holes
We develop and discuss a model formalism to study the properties of mass
outflows that are emerged out from a relativistic, magnetized, viscous,
advective accretion flow around a rotating black hole. In doing so, we consider
the toroidal component as the dominant magnetic fields and synchrotron process
is the dominant cooling mechanism inside the accretion disk. With this, we
self-consistently solve the coupled accretion-ejection governing equations in
the steady state and obtain the shock-induced global inflow-outflow solutions
in terms of the inflow parameters, namely plasma- (, and being gas and magnetic pressures),
accretion rates () and viscosity (), respectively.
Using these solutions, we compute the mass outflow rate (, the
ratio of outflow to inflow mass flux) and find that mass loss from the
magnetized accretion disk continues to take place for wide range of inflow
parameters and black hole spin (). We also observe that
strongly depends on plasma-, , and ,
and it increases as the magnetic activity inside the accretion disk is
increased. Further, we compute the maximum mass outflow rate () by freely varying the inflow parameters and find that for
magnetic pressure dominated disk, () for (). Finally, while discussing the implication
of our model formalism, we compute the maximum jet kinetic power using which appears to be in close agreement with the observed jet
kinetic power of several black hole sources.Comment: 14 pages, 8 figures, 1 table, Comments welcom
Formation of non-steady outflows and QPOs around black hole
We study the time dependent properties of sub-Keplerian viscous accretion
flow around the black holes. We find that rotating matter feels centrifugal
barrier on the way towards the black holes and eventually, shock transition is
triggered allowing a part of the post-shock matter to eject out as bipolar
outflow. This outflowing matters are supposed to be the precursor of
relativistic jets. As viscosity is increased, shock becomes unsteady and start
to oscillate when viscosity reached its critical value. This causes the inner
part of the disk unsteady resulting periodic ejection of matter from the
post-shock region. Also, the same hot and dense post-shock matter emits high
energy radiation which modulates quasi-periodically. The power density spectra
confirms this features as most of the power is concentrated at a narrow
frequency range --- a characteristics (i. e. Quasi-Periodic Oscillation)
commonly seen in several outbursting black hole candidates.Comment: 6 Pages, 4 figures, RECTO 2013 conference proceedings published in
Astronomical Society of India Conference Serie
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