Abstract:

I checked the DARM error spectrum when the violin mode was kicked strongly.
The kicked suspension (or at least resonances) seem to be different between two different timing.
he kicked suspension should be idntified by exciting violin mode to investigate the glitch sources.

Detail:

Today, we observed clear peak around 180 Hz when PRFPMI was locked with RF signals, so I measured the spectrum at that time with 0.008 Hz bandwidth (fig1).
Red shows the spectrum around 2025/03/17 08:18 UTC and blue shows the spectrum around 2025/03/17 06:51 UTC.
There are large peaks at 178.94, 180.25, and 182.91 Hz in red graph while there are at 181.91 and 183.25 Hz in blue.

It is necessary to identify which suspension is kicked by intentionally exciting the violin mode but it is very likely that different suspensions were kicked because it is hard to excite not all fibers by chance.
Also, ETMY violin mode was higher/lower frequencies (around 165 Hz and 190 Hz), it is not likely tobe ETMY violin mode.
So, we suspected the cooling of the mirror might cause the glitches but out guess should be carefully checked.