Universal Correlation Scale Echoes in LIGO O3 Residuals and the Emergent Constant L

We analyse 326 publicly available LIGO O3 gravitational wave events and compute the post-merger residual after subtraction of the official detector waveform model. Each event is rescaled by the black-hole thermal timescale TBH, and the residual autocorrelation is stacked across the full dataset. A universal and statistically stable correlation feature appears at tau/TBH = 4. This value coincides exactly with the theoretical prediction 1/L derived from a closed quartic variational framework, where L = 0.25 emerges as a structural constant without tuning or free parameters. The detection of a scale-invariant correlation in real interferometric data suggests that a universal physical effect has been present in LIGO observations since O1 but remained hidden due to inappropriate analysis variables. This result constitutes the first indirect empirical support for the constant L.