Florent mentioned a "line of glitches" around 460 Hz whose source may be a non-stationary frequency line around 460 Hz, described by Gabriele as "first order violin modes of the last
stage of cavity mirror suspension". In June, such, there are lots of such 460 Hz glitches.
Looking at today's omegagram, we can see a lot of loud (snr>10) glitches also around an other frequency near 500 Hz (plot 1). The corresponding omega triggers are tagged with a frequency 498 Hz or 493 Hz. Plot2 shows the dark fringe spectrogram, early today. We clearly see some lines (some of them non-stationary on a short time scale) but none are around 500 Hz.
Computing band rms around each frequency line visible on the plot 2 and looking at the spectrum of it (plots 3 and 4), I found the usual 0.6 Hz for several of them but also some unusual (to me) low frequencies:
spectrum peak for band rms 350-352 Hz : 0.5 Hz
spectrum peak for band rms 443-445 Hz : 0.18 Hz, 0.67 Hz
spectrum peak for band rms 463-465 Hz : 0.07, 0.14, 0.17, 0.22
spectrum peak for band rms 468-470 Hz : 0.07, 0.14, 0.17, 0.22
But no hint for the 493 Hz and 498 Hz glitches. It would be interesting to know better how the frequencies of the omega triggers can be correlated to frequencies of non-stationary lines.
It would be interesting also to have some hints for the non-stationarity low frequencies above.
