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TAPIR Seminar

Friday, February 24, 2023
2:00pm to 3:00pm
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Online and In-Person Event
On the modeling of black hole ringdown: quasi-normal modes and graybody factors
Naritaka Oshita, Special Postdoctoral Researcher, Interdisciplinary Theoretical and Mathematical Sciences Program (iTHEMS), RIKEN,

In person: 370 Cahill -- Attendees joining in person must have a valid Caltech UID.

To Join via Zoom: 864 8902 5566

ABSTRACT: A gravitational wave from a binary black hole merger is an important probe to test gravity. Especially, the observation of ringdown may allow us to perform a robust test of gravity as it is a superposition of excited quasi-normal (QN) modes of a Kerr black hole. The excitation factor is an important quantity that quantifies the excitability of QN modes and is independent of the initial data of black hole mergers.

In this talk, I will show which QN modes can be important (i.e., have higher excitation factors) and will discuss how we can determine the start time of ringdown to maximally enhance the detectability of the QN modes.

Also, I will introduce my recent conjecture on the modeling of ringdown waveform: the thermal ringdown model in which the ringdown spectrum of a small mass ratio merger involving a massive and rapidly spinning black hole can be modeled by the graybody factor of the black hole, which is similar to the Fermi-Dirac distribution.

For more information, please contact JoAnn Boyd by phone at 626-395-4280 or by email at [email protected].