Odd-parity ringdown gravitational waves of a spherically symmetric black hole with perfect fluid accretion
Abstract
The ringdown waves from a black hole offer a clean probe of strong-field gravity, but a matter distribution that may be present around a realistic black hole renders the background spacetime dynamical and the ringdown frequencies time-dependent. We study the odd-parity ringdown of a Schwarzschild black hole that grows through the dilute, steady, spherically symmetric accretion of a perfect fluid. Working to first order in the accretion rate, we compute the ringdown waveform directly in the time domain on this dynamical background. Since the odd-parity matter perturbation decouples from the metric perturbation, the wave mode can be described by a purely tensorial mode on the accreting background. In particular, the ratio of the imaginary to the real part of the frequency cancels both the secular variation caused by the growth of the black hole and the redshift factor, so that its deviation from the Schwarzschild value purely reflects the surrounding environment. The time dependence of the frequency, on the other hand, reflects the accretion rate and allows us to define a second observable tied to it. We argue that measuring these observables across multiple modes may provide significant information to constrain the surrounding environment of the black hole.
Versions
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BibTeX
@misc{ohashi2026oddparity,
title = {{Odd-parity ringdown gravitational waves of a spherically symmetric black hole with perfect fluid accretion}},
author = {Rikuto Ohashi and Yasutaka Koga and Hiroyuki Nakano and Kota Ogasawara and Chul-Moon Yoo},
howpublished = {arXiv},
year = {2026},
month = nov,
doi = {10.48550/arxiv.2607.03231},
eprint = {2607.03231},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.03231},
}
RIS
TY - UNPB
TI - Odd-parity ringdown gravitational waves of a spherically symmetric black hole with perfect fluid accretion
AU - Rikuto Ohashi
AU - Yasutaka Koga
AU - Hiroyuki Nakano
AU - Kota Ogasawara
AU - Chul-Moon Yoo
PY - 2026
DA - 2026/11/03
PB - arXiv
DO - 10.48550/arxiv.2607.03231
UR - https://arxiv.org/abs/2607.03231
AB - The ringdown waves from a black hole offer a clean probe of strong-field gravity, but a matter distribution that may be present around a realistic black hole renders the background spacetime dynamical and the ringdown frequencies time-dependent. We study the odd-parity ringdown of a Schwarzschild black hole that grows through the dilute, steady, spherically symmetric accretion of a perfect fluid. Working to first order in the accretion rate, we compute the ringdown waveform directly in the time domain on this dynamical background. Since the odd-parity matter perturbation decouples from the metric perturbation, the wave mode can be described by a purely tensorial mode on the accreting background. In particular, the ratio of the imaginary to the real part of the frequency cancels both the secular variation caused by the growth of the black hole and the redshift factor, so that its deviation from the Schwarzschild value purely reflects the surrounding environment. The time dependence of the frequency, on the other hand, reflects the accretion rate and allows us to define a second observable tied to it. We argue that measuring these observables across multiple modes may provide significant information to constrain the surrounding environment of the black hole.
ER -