Correcting misspecification of calibration uncertainties in gravitational-wave data analysis with efficient reweighting

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LIGO-T2500295-v3
25 Sep 2025, 04:25

Abstract:: Ground-based gravitational-wave detectors require calibration to map the measured output of the interferometer to gravitational-wave strain. This calibration has uncertainties that vary across the frequency band of the detectors; these uncertainties are included in analyses that infer the source properties of gravitational-wave signals. During the fourth observing run of the LIGO--Virgo--KAGRA network, it was discovered that there was an error in how uncertainties for LIGO calibration were handled in these analysis, with a mismatch between the output of the calibration calculation and the assumed input for the source-property inference. For data from the first three observing runs, this should have a small impact on results, as the calibration uncertainties had near-zero means. We present an efficient method to reweight inference results to correct the calibration uncertainties. We verify the accuracy of reweighting through comparison with a selected subset of rerun analyses. Using the reweighting algorithm, we are able to confirm that the error in calibration conventions does not significantly impact any conclusions of previous analyses, with the most significant difference being for the inferred right ascension for GW150914.

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LIGO Document T2500295-v5