No Sidereal-Phase-Locked Transient Coincidences in IGETS Superconducting Gravimeter Records:\\ A Controlled Null Detection

We perform a controlled search for sidereal-phase-locked transientcoincidences in superconducting gravimeter records from theInternational Geodynamics and Earth Tide Service (IGETS).We analyse two high-quality stations (, Rustrel/LSBB iGrav;, Strasbourg iOSG) using (i) a window-based pipeline onLevel-1 minute data (2020--2024) and (ii) an independentband-limited variability proxy on Level-1 second data(January 2024), derived from robust z-scored rolling RMS ofbandpass-filtered gravity in two bands (1--6\,h and 10--60\,min).Sidereal-selected windows exhibit strong cross-station structure(e.g.\ Spearman ≈ 0.712 for 2020--2024,$n=5431$ pairs) and elevated joint tail activity relative torandom windows, consistent with selection of globally active epochs.However, timing specificity is not supported: the decisivesolar-time control (Gate-S), constructed by a $+182$-day circularshift of the sidereal driver-window schedule within 2024, yields acorrelation statistically indistinguishable from the siderealschedule (≈ 0.927 vs.\ ≈ 0.917;=0.010, empirical two-sided ≈ 0.42).A full re-evaluation shift null also does not reject the null(≈ 0.10 in 2024).The second-resolution proxy analysis likewise shows no significantSID--RAND advantage for correlation or tail-weight summaries.We therefore report a null detection of sidereal-phase-lockedtransient coupling under the tested pipelines and provideconservative bounds on any timing-specific enhancement.