[Yuzurihara, Ishikawa]
We started the investigation of the non-stationary noise, using data from 2025/06/06 - 2025/08/15.
During this period, short-term drops in the inspiral range occurred frequently. The rate is several times per hour. We developed a method to identify those times by using the exponential moving average. At that time, we saw the excess of the line noise and the its damping decay. We identified and listed the frequencies of the damping decay from the ASD at the times of the drop of the inspiral range.
The figures on pages 1 and 2 show examples.

• The top-left figure shows the inspiral range over a one-hour period including a drop.
• The top-right figure shows the ASD between 20 Hz and 200 Hz, where blue indicates the short segment around the drop and orange indicates the reference.
• The bottom-right figure shows their ratio.
• The bottom-left figure shows an example of a time series band-passed around the peak frequency.

The figure on page 3 of the slide shows the histogram of the number of occurrences of excess power at these frequencies during the analyzed interval. This preliminary result might include the different non-stationary noise from the damping decay. We will continue the analysis.
Detailed plots can be found in the JGWdoc.