34 citations · 36 across the 2 of their papers we have counts for
5 papers
Shadow formation in gravitational collapse: Redshift and blueshift by spacetime dynamics
Yasutaka Koga, Nobuyuki Asaka, Masashi Kimura +1
A black hole illuminated by a background light source is observed as a black hole shadow. For a black hole formed by gravitational collapse of a transmissive object, redshift of li…
Dynamical photon sphere and time evolving shadow around black holes with temporal accretion
Yasutaka Koga, Nobuyuki Asaka, Masashi Kimura +1
A photon sphere is known as the geometrical structure shaping a black hole shadow. The mechanism is well understood for static or stationary black hole spacetimes such as the Schwa…
Do black hole shadows merge?
Kazumasa Okabayashi, Nobuyuki Asaka, Ken-ichi Nakao
The so-called black hole shadow is not a silhouette of a black hole but an image of a collapsing object or a white hole. Hence it is non-trivial whether black hole shadows merge wi…
Maximal Efficiency of Collisional Penrose Process with Spinning Particle II
Kazumasa Okabayashi, Kei-ichi Maeda
We analyze the collisional Penrose process between a particle on the ISCO orbit around an extreme Kerr black hole and a particle impinging from infinity. We consider both cases wit…
Maximal Efficiency of Collisional Penrose Process with Spinning Particles
Kei-ichi Maeda, Kazumasa Okabayashi, Hirotada Okawa
We analyze collisional Penrose process of spinning test particles in an extreme Kerr black hole. We consider that two particles plunge into the black hole from infinity and collide…