This entry is related with the Elog38943 and Elog38996.

I have run the coherence with different accelerometers around Virgo and the different lines between 255Hz and 269Hz show an important coherence with many accelerometers in the central building, but specialy with some  accelerometers around the NI that are coherent for 255Hz and the band between 265-269Hz. In the case of the WI there is some coherence, but less than in NI. The range between 265-269Hz also shows coherence with PR, SPRB and B4Ghost. No coherence is seen with SWEB and SNEB.

Also, plotting all the accelerometers inside the central building it is possible to see that some of them have spectral lines coincident with the lines present in hrec (the most remarcable are related with NI). This can be seen in fig2 where the pink line is the signal of the DT accelerometer, the purple line is V1:ENV_NI_ACC_X and the yellow-ish line is the NI_LINK_ACC. Whether the coupling is done in NI or not the fact that the accelerometers show a more intense signal at those frequencies isn't that meaning the source of noise should be closer to NI?

Just to remember, as is explained in 38943 those lines drift their frequency as a common group.