Butterworth filter with knee frequency of 11 Hz to avoid spectral leakage from the noise power spectrum below 20 Hz. Next we apply a Fourier transform to segments with a duration of 192 s, using 50% overlapping Hann windows, then we coarse-grain six frequency bins to obtain a frequency resolution of 1/32 Hz. As in [@stoch_O1], we observe in the band 20-1726 Hz. The maximum frequency of 1726 Hz is chosen to avoid aliasing effects after downsampling the data.

Next, we apply a series of data quality cuts that remove non-Gaussian features of the data. We remove times when the detectors are known to be unsuitable for science results [^2] and times associated with known gravitational-wave events [@gwtc-1]. We also remove times where the noise is non-stationary, following the procedure described in the supplement of  [@S5StochIso] (see also [@stoch_O1]). These cuts remove % of the coincident time which is in principle suitable for data analysis, leading to a coincident livetime of .

In the frequency domain, we remove narrowband coherent lines that are determined to have instrumental or environmental causes, using the methods described in [@CWStochDetchar]. These cuts remove % of the total observing band, but only % of the 