We consider stationary, axially and equatorially symmetric systems consisting of a central rotating and charged degenerate black hole and surrounding physically realistic matter. We show that a + Q = M always holds, where a = J/M is the black hole’s intrinsic angular momentum per unit mass, Q its electric charge and M the well known black hole mass parameter introduced by Christodoulou and Ruff...

We elucidate the feature of gravitational waves (GWs) from a binary-neutron-star merger collapsing to a black hole by general relativistic simulation. We show that GW spectrum imprints the coalescence dynamics, formation process of disk, equation of state for neutron stars, total masses, and mass ratio. A formation mechanism of the central engine of short-gamma-ray bursts, which are likely to b...

Roll forming process is used for manufacturing sheet metal parts by successive bending and creating the final shape with gradual deformation. In this article, deformation of a pre-punched sheet due to the roll forming process was studied. Two main defects in the roll forming process are ovality of holes and bow defect. The ovality of the hole is influenced by the process parameters including sh...

Reverberation mapping is a proven technique that is used to measure the size of the broad emission-line region and central black hole mass in active galactic nuclei. More ambitious reverberation mapping programs that are well within the capabilities of Hubble Space Telescope could allow us to determine the nature and flow of line-emitting gas in active nuclei and to assess accurately the system...

We report on the detection of a thermal disc component from the stellar-mass black hole binary XTE J1118+480 in the canonical low/hard state. The presence of a thermal component with a temperature of approximately 0.21 keV in the Chandra spectra of XTE J1118+480 is found at more than the 14σ confidence level. Based on this evidence, we argue that the accretion disc in XTE J1118+480 is not trunc...

We propose a scenario in which massive stars form at the outer edges of an AGN accretion disc. We analyze the dynamics of a disc forming around a supermassive black hole, in which the angular momentum is transported by turbulence induced by the disc’s self-gravity. We find that once the surface density of the disc exceeds a critical value, the disc fragments into dense clumps. We argue that the...