In the data downloaded from GWOSC, the data’s asd/psd contain spectra lines. I found some information of instrumental lines in LIGO, for example, O1 data has:
But I don’t quite understand the parameters in the file provided at the bottom, for example, what is index of first visible harmonic/index of last visible harmonic? Is there a document explaining all these things in detail? Or can someone help me understand those parameters?
Also, I wonder is an official method for line removal?
Hi @BarryG ! Thank you for your question.
The key to understanding these column names is included in the file:
% For fixed-width combs, veto the band:
% [offset+index*spacing-leftwidth, offset+index*spacing+rightwidth]
% For scaling-width combs, veto the band:
% [offset+index*spacing-index*leftwidth, offset+index*spacing+index*rightwidth]
So, for example, the 60 Hz line is a “comb with fixed width”, and has lines at 60 Hz, 120 Hz, 180 Hz, etc. up to 9*60 Hz = 540 Hz.
There is no one method to remove lines. Many transient searches whiten the data, with no extra step to remove the lines in particular. Continuous wave searches, which are typically done in the frequency domain, may entirely remove data and/or veto triggers that fall within the bandwidth of a line.
@jonah Thank you for your patience! I’ve come to realize that visible harmonics represent frequencies that are integer multiples of the base frequency. I now have a clearer understanding of data conditioning in this context.
Have a nice day!!!