Binary merger: orbital decay, chirp waveform h(t) ∝ f^(2/3), chirp mass ℳ
Inspiraling binaries lose energy to gravitational radiation at rate dE/dt = −32/5 · G⁴/c⁵ · (m₁m₂)²(m₁+m₂)/r⁵. The chirp mass ℳ = (m₁m₂)^(3/5)/(m₁+m₂)^(1/5) governs the waveform frequency evolution f(t) ∝ (t_c−t)^(−3/8). GW150914 detected by LIGO in 2015 had ℳ ≈ 28.3 M☉.