The NoEMi (Noise Frequency Event Miner) framework

The data collected by a gravitational wave interferometer are inevitably affected by instrumental artefacts and environmental disturbances. In particular, for continuous gravitational wave (CW) studies it is important to detect narrow-band disturbances (the so-called "noise lines") during science runs, and to help scientists to identify and possibly remove or mitigate their sources. The NoEMi (Noise Frequency Event Miner) framework exploits some of the algorithms implemented for the CW search to identify, on a daily basis, the frequency lines observed in the Virgo science data and in a subset of the environmental sensors, looking for lines that match in frequency. A line tracker algorithm reconstructs the lines over time, and stores them in a database, which is made accesible via a web interface. We describe the workflow of NoEMi, providing examples of its use for the investigation of noise lines in past Virgo runs (VSR2, VSR3) and in the most recent run (VSR4)

Characterization of the LIGO detectors during their sixth science run

In 2009-2010, the Laser Interferometer Gravitational-Wave Observatory (LIGO) operated together with international partners Virgo and GEO600 as a network to search for gravitational waves (GWs) of astrophysical origin. The sensitivity of these detectors was limited by a combination of noise sources inherent to the instrumental design and its environment, often localized in time or frequency, that couple into the GW readout. Here we review the performance of the LIGO instruments during this epoch, the work done to characterize the detectors and their data, and the effect that transient and continuous noise artefacts have on the sensitivity of LIGO to a variety of astrophysical sources