The problem of constructing global models describing isolated axially symmetric rotating bodies in equilibrium is analyzed. It is claimed that, whenever the global spacetime is constructed by giving boundary data on the limiting surface of the body and integrating Einstein’s equations both inside and ouside the body, the problem becomes overdetermined. Similarly, when the spacetime describing t...

In this paper we present a fully relativistic approach to modelling both the continuum emission and the reflected fluorescent iron line from a primary X-ray source near a Kerr black hole. The X-ray source is located above an accretion disc orbiting around the black hole. The source is assumed to be a static point source located on an arbitrary position above the disc, on or off the axis of rota...

γ Cassiopeia (γ Cas), is known to be a binary system consisting of a Be-type star and a low-mass (M ∼ 1M ) companion of unknown nature orbiting in the Be-disc plane. Here, we apply the quasi-spherical accretion theory on to a compact magnetized star and show that if the low-mass companion of γ Cas is a fast spinning neutron star, the key observational signatures of γ Cas are remarkably well rep...

ABSTRACT We study the radiatively driven fluid jets around a non-rotating black hole. The radiation arising from inner compact corona and outer sub-Keplerian part of disc accelerates jets. obtain steady state, semi-analytical, outflow solutions. thermodynamics is described by variable adiabatic index equation state. develop total variation diminishing (TVD) routine to investigate time dependent...

The purpose of this note is mainly pedagogical. An apparent paradox will be described which arises in this connection. From the resolution of this paradox one may learn two things. First, one realizes that there are, in a certain sense, two different kinds of Lorentz contractions. Secondly, one sees most clearly how the nonEuclidean space geometry comes into being if the disc is set rotating. C...

Transient spectral features have been discovered in the X-ray spectra of Active Galactic Nuclei, mostly in the 5–7 keV energy range. Several interpretations were proposed for the origin of these features. We examined a model of Doppler boosted blue horns of the iron line originating from a spot in a black hole accretion disc, taking into account different approximations of general relativistic ...

Continuous flow spinning disc processing (SDP), which has extremely rapid mixing under plug flow conditions, effective heat and mass transfer, allowing high throughput with low wastage solvent efficiency, is effective in gaining access to superparamagnetic Fe3O4 nanoparticles at room temperature. These are formed by passing ammonia gas over a thin aqueous film of Fe which is introduced through ...

Rotating accretion flow may undergo centrifugal pressure mediated shock transition even in presence of various dissipative processes, such as viscosity and cooling mechanism. The extra thermal gradient force along the vertical direction in the post shock flow drives a part of the accreting matter as bipolar outflows which are believed to be the precursor of relativistic jets. We compute mass lo...

We report spectral results from three BeppoSAX observations of the black hole candidate XTE J1650–500 during its 2001/2002 outburst. We find strong evidence for the presence of a broad and strongly relativistic Fe emission line. The line profile indicates an accretion disc extending down to two gravitational radii suggesting the presence of a rapidly rotating central Kerr black hole. Thanks to ...

The spin-down of Be stars due to angular momentum transport from star to disc has been considered. This has been prompted by empirical studies of observed optical and IR line profile studies indicating that the disc is rotating in a Keplerian fashion. It is found that substantial spin-down may occur, especially for late B stars throughout their main-sequence lives for the “strongest” discs (mos...