Following up on the loud wandering line around 1180Hz seen in the May 3rd lock (figure 1), we see this line in DARM as coherent with similar lines in SRCL, PRCL, MICH, IMC-I, IMC-F and PSL-FSS_TPD_DC_OUT_DQ. figure 2 shows the stamp-pem coherence matrix for the ~90 minutes of lock from 1114597337-1114600937 where each cell represents coherence for a single frequency and channel. The coherent channels are labeled in the plot.

In addition, representative cross-power spectrograms (where color represents STAMP SNR, effectively a measure of coherence) for an hour of data in this time for SRCL and PSL-FSS_TPD_DC_OUT_DQ can be seen in figures 3,4 that show the nature of this line. There is also a strong wandering line between 1150 and 1160 Hz that is seen in PSL-FSS_TPD_DC_OUT_DQ (PSD, figure 5) and that is also coherent in DARM (see figure 4). This line, however, is not obvious in the DARM PSD spectrograms. 

These PSD and cross-power spectrograms were made using 60s ffts and coarse-graned to 1Hz frequency bins. 

Each of PRCL, SRCL, and MICH also show coherence with the 1150Hz stationary line seen in DARM, while the IMC and PSL channels do not. See (18277) for a discussion of this line.