Accretion process onto super-spinning objects (2009)
Bambi, Cosimo, Freese, Katherine, Harada, Tomohiro, Takahashi, Rohta, Yoshida, Naoki
The accretion process onto spinning objects in Kerr spacetimes is studied with numerical simulations. Our results show that accretion onto compact objects with Kerr parameter (characterizing the...
Huang, Lei, Takahashi, Rohta, Shen, Zhi-Qiang
The vicinity of the supermassive black hole associated with the compact radio source Sagittarius (Sgr) A* is believed to dominate the observed emission at wavelengths near and shorter than $\sim$ 1...
Is the Carter-Israel conjecture correct? (2009)
Bambi, Cosimo, Freese, Katherine, Takahashi, Rohta
According to the Carter-Israel conjecture, the end-state of the gravitational collapse of matter is a Kerr-Newman black hole. Nevertheless, neither the theory nor observations can confirm that. In...
An Approach Detecting the Event Horizon of Sgr A* (2008)
Miyoshi, Makoto, Kameno, Seiji, Ishituka, Jose K., Shen, Zhi-Qiang, Takahashi, Rohta, Horiuchi, Shinji
Imaging the vicinity of a black hole is one of the ultimate goals of VLBI astronomy. The closest massive black hole, Sgr A*, located at the Galactic center, is the leading candidate for such...
Equations of fully general relativistic radiation hydrodynamics around a rotating black hole are derived by using the Kerr-Schild coordinate where there is no coordinate singularity at the event...
Equations of general relativistic radiation hydrodynamics in Kerr space-time (2007)
Equations of fully general relativistic radiation hydrodynamics in Kerr space-time are derived. While the interactions between matter and radiation are introduced in the comoving frame, the...
Horizon-Penetrating Transonic Accretion Disks around Rotating Black Holes (2007)
The stationary hydrodynamic equations for the transonic accretion disks and flows around rotating black holes are presented by using the Kerr-Schild coordinate where there is no coordinate...
Advection-dominated accretion flows with causal viscosity (2007)
We present the basic equations and sample solutions for the steady-state global transonic solutions of the advection-dominated accretion flows (ADAFs) with a causal viscosity prescription. The...
Takahashi, Rohta, Watarai, Ken-Ya
We calculate eclipsing light curves for accretion flows around a rotating black hole taking into account the atmospheric effects of the companion star. In the cases of no atmospheric effects, the...
Numerical study of gamma-ray burst jet formation in collapsars (2007)
Nagataki, Shigehiro, Takahashi, Rohta, Mizuta, Akira, Takiwaki, Tomoya
Toward understanding the central engine of long GRBs (2007)
Nagataki, Shigehiro, Takahashi, Rohta, Mizuta, Akira, Takiwaki, Tomoya
Eclipsing Light-Curve Asymmetry for Black-Hole Accretion Flows (2005)
Watarai, Ken-ya, Takahashi, Rohta, Fukue, Jun
We propose an eclipsing light-curve diagnosis for black-hole accretion flows. When emission from an inner accretion disk around a black hole is occulted by a companion star, the observed light curve...
Black Hole Shadows of Charged Spinning Black Holes (2005)
We propose a method for measuring the black hole charge by imaging a black hole shadow in a galactic center by future interferometers. Even when the black hole is uncharged, it is possible to confirm...
Can we determine a spin parameter of a black hole by observation of a black hole shadow in an accretion disk? In order to answer this question, we make a qualitative analysis and a quantitative...
X-Ray Microlensing of Bright Quasars (2001)
Takahashi, Rohta, Yonehara, Atsunori, Mineshige, Shin
We calculated the expected microlens light curves for several accretion-flow models and compared the results to find what aspects of distinct flow structures can be extracted from the microlens light...