LIGO Document P2100439-v1
- The Advanced Laser Interferometer Gravitational-wave Observatory (LIGO) is a science facility in the United States devoted to the observation of gravitational waves (GWs). It comprises two kilometer-scale laser interferometers. It is a part of a global ground-based GW detector network that also includes Virgo in Italy and KAGRA in Japan. Calibration of the LIGO detectors is achieved using displacement fiducials generated by radiation pressure based systems called Photon Calibrators (Pcals). The first part of this research described here details the developments implemented during the third LIGO-Virgo-KAGRA (LVK) observation run, O3, in the propagation of laser power calibration via transfer standards to on-line power sensors. These developments have enabled generation of length fiducials with improved accuracy of 0.41 %. This estimated uncertainty is almost a factor of two smaller than the lowest values previously reported. This result enabled reducing the uncertainty in overall calibration of the LIGO interferometers during the O3 observing run to the 2 % level.
GW source parameter estimation and localization rely on accurately calibrated strain data. The second part of the research reported here investigates the impact of overall, systematic detector calibration errors on the sky localization of burst-like GW sources, specifically core collapse supernovae (CCSN). This analysis is performed using simulated waveforms from different CCSN models and one of the standard LVK pipelines used to search for burst-like GW signals. Overall calibration errors as large as ±10 % are imposed on a single detector in the LIGO-Virgo network. Preliminary results indicate that this causes average changes in the area of 90 % sky localization confidence regions as large as 18 %. Associated average errors in estimated probabilities for these regions are as large as 5 %. Furthermore, for sources located in some regions of the sky, source localization errors are as large as 90 %, indicating that counterparts to GW signals would not be found within the 90 % confidence regions in follow-up observations by electromagnetic observatories.
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