LIGO Document T1800505-v2

PEM Vetting Report For GW150914

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T - Technical notes
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PEM vetting report entered into the event logbook for the first detection.

PEM spectra from the time of the event were checked by multiple people for anomalies or malfunctioning channels. About 15% of PEM channels had not been installed or were not working at the time of the candidate, but redundant channels provided good coverage. We checked Omega Scan configuration files to make sure the necessary channels and bands were searched. Since Omega Scans are limited to a 4096 sample rate, and vibrations over 2500 Hz have been shown to down-convert into the 200 Hz region of DARM, we checked relevant PEM spectra directly for high frequency events. Coupling estimates from PEM injections were used to calculate the estimated SNR in DARM for every PEM channel that triggered Omega Scan in 30-350 Hz band during the second around the candidate, without regard to the time-frequency path. The loudest PEM event would have had to be at least (upper limit) 17 times louder in order to produce an event in DARM with the same SNR as the candidate. Potential environmental mechanisms for producing the Sept. 14 candidate are discussed and rejected. In summary we have found no reason to doubt that the candidate represents the first direct detection of gravitational waves.

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