Ken-ichi Oohara

Structure of Superposed Two Kerr Metrics

Properties of the superposed two Kerr metrics derived by Kramer and Neugebauer are examined. Particularly, the structure of the infinite redshift surfaces is given by changing the distance between the two Kerr metrics.

Gravitational radiation emitted by N particles in circular orbits

Abstract We have computed the gravitational radiation emitted by N particles of equal mass in a circular orbit around a Schwarzschild black hole. It is found that the luminosity decreases sharp with the increase of N due to the phase cancellation effect. The application of the Bekensteins octopole formula shows the decay time of the orbit of a triple compact star each of mass 1.4 M ⊚ with a period of 10 min can be 5.4 x 10 9 yr.

Energy, momentum and angular momentum of gravitational radiation from a particle plunging into a non-rotating black hole

Abstract We have computed the energy Δ E , the momentum Δ P and the angular momentum Δ J of gravitational radiation induced by a particle of mass μ and angular momentum μ L z plunging into a Schwarzschild black hole of mass M (⪢μ). It is found that the maximum value of Δ P is 4.5 × 10 −2 ( μ / M ) μc , ΔE / ΔJ ≈ 0.15 c /( GM / c 2 ), and a rotating ring plunging into a black hole emits less energy than a non-rotating one.

Gravitational radiation from a particle scattered by a non-rotating black hole

Abstract We have analyzed the gravitational radiation emitted by a particle of mass μ and angular momentum μ L z [>4μ( GM / itc 2 ) c ] scattered by a Schwarzschild black hole of mass M (⪢μ). It is found that the quasi-normal mode is not excited even when the periastron approaches the limiting value 4 GM / c 2 . The total energy for L z = 4.1 ( GM / c 2 ) c is 1.24 x 1 (μ/ M ) c 2 , which is smaller than for L z = 3.9 ( GM / c 2 ) c .

Apparent horizons of time-symmetric initial value for three black holes

Abstract The apparent horizon of three black holes on a time-symmetric space-like hypersurface is examined. The area is computed for various values of separation parameters. Using Hawkings mass formula, we found that the maximum possible efficiency of energy release is no more than 8.44 × 10 -3 when the initial apparent horizon encloses three black holes.

Excitation of the Free Oscillation of a Schwarzschild Black Hole by the Gravitational Waves from a Scattered Test Particle

On etudie les ondes gravitationnelles rayonnees par une particule depreuve de masse μ et de moment angulaire orbital μLz partant de linfini avec une vitesse finie (1-e −2 ) 1/2 •c et diffusee par un trou noir de Schwarzschild de masse M (>>μ)