34 citations
3 papers
gr-qc2025
Probing higher curvature gravity via ringdown with overtones
Keisuke Nakashi, Masashi Kimura, Hayato Motohashi +1
We investigate metric perturbations of a spherically symmetric black hole in higher curvature gravity. We show that higher curvature corrections deform the near-horizon region of t…
gr-qc2025★ 2 cited
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…
gr-qc2022★ 34 cited
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…