Regression of Suspension Violin Modes in KAGRA O3GK Data with Kalman Filters

Abstract

Suspension thermal modes in interferometric gravitational-wave detectors produce narrow, high-Q spectral lines that can contaminate gravitational searches and bias parameter estimation. In KAGRA, cryogenic mirrors are held by thick suspension fibers, designed to sustain such a low-temperature environment, which may further affect inharmonicity modes, fiber dimensions, and mechanical behavior compared to typical interferometers. As these modes remain a prominent source of narrowband contamination, we implement a Kalman filter to model and track violin lines, building on the methodology introduced in [1], and apply subtraction to KAGRA O3GK data. Using gravitational-wave template injections, we validate that the subtraction preserves matched-filter SNR while effectively suppressing line power. Comparisons of power spectral densities and residual analyses confirm that the method removes deterministic line contributions without introducing waveform distortions. This approach provides a cleaner strain channel for searches and parameter estimation and will become increasingly important for future low-temperature detectors with higher-Q suspensions, such as the Einstein Telescope.

arXiv comment13 pages, 15 figures

References in corpus (5)

• The PyCBC search for gravitational waves from compact binary coalescence
• FINDCHIRP: an algorithm for detection of gravitational waves from inspiraling compact binaries
• A chi-squared time-frequency discriminator for gravitational wave detection
• Performance of the KAGRA detector during the first joint observation with GEO 600 (O3GK)
• Data conditioning for gravitational wave detectors: A Kalman filter for regressing suspension violin mode