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 f_cut(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: R_eff = 1 for f < f_cut(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 M_crit = 14.75 M☉, f_cut → 0 and the object becomes GW-transparent, producing a continuous transition in echo amplitude at the phase boundary. Einstein Telescope can measure f_cut(M) for mergers within ~200 Mpc.