P61: Spectral Signature of CCEGA Black Stars — A Mass-Dependent Frequency Cutoff in GW Echo Spectra

We analyze the Regge-Wheeler potential structure of CCEGA black stars and identify a mass-dependent spectral cutoff fcut (M) ≈ 2, 200–8, 000 Hz. The potential cavity is too narrow to support discrete QNM resonances. Instead, the interior barrier produces a frequency-dependent reflection coefficient: Rₑff = 1 for f < fcut (M), falling rapidly above it. The cutoff decreases monotonically with mass, acting as a gravitational wave mass spectrometer — measuring the echo rolloff frequency determines the black star mass independently of the merger waveform. Near Mcrit = 14. 75 M☉, fcut → 0 and the object becomes GW-transparent, producing a continuous transition in echo amplitude at the phase boundary. Einstein Telescope can measure fcut (M) for mergers within ~200 Mpc.