Gravitational Wave Ringdown — Quasi-Normal Modes

Black Hole Parameters

Mass M (M☉): 60 Spin a/M: 0.68 Inclination θ: 30° SNR: 20 Modes displayed ℓ=2,m=2 (dominant) ℓ=2,m=1 ℓ=3,m=3

f₂₂ (QNM): — Hz
τ₂₂ (decay): — ms
Quality Q: —
Fitted f: — Hz
Fitted τ: — ms

After a binary black hole merger, the remnant "rings down" by emitting gravitational waves — quasi-normal modes (QNMs) characterized by complex frequencies. The dominant l=2,m=2 mode frequency and damping time encode the final mass and spin. This is a test of the Kerr no-hair theorem.