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Free keywords:
General Relativity and Quantum Cosmology, gr-qc, Astrophysics, Instrumentation and Methods for Astrophysics, astro-ph.IM, Physics, Instrumentation and Detectors, physics.ins-det
Abstract:
In Advanced LIGO, detection and astrophysical source parameter estimation of
the binary black hole merger GW150914 requires a calibrated estimate of the
gravitational-wave strain sensed by the detectors. Producing an estimate from
each detector's differential arm length control loop readout signals requires
applying time domain filters, which are designed from a frequency domain model
of the detector's gravitational-wave response. The gravitational-wave response
model is determined by the detector's opto-mechanical response and the
properties of its feedback control system. The measurements used to validate
the model and characterize its uncertainty are derived primarily from a
dedicated photon radiation pressure actuator, with cross-checks provided by
optical and radio frequency references. We describe how the gravitational-wave
readout signal is calibrated into equivalent gravitational-wave-induced strain
and how the statistical uncertainties and systematic errors are assessed.
Detector data collected over 38 calendar days, from September 12 to October 20,
2015, contain the event GW150914 and approximately 16 of coincident data used
to estimate the event false alarm probability. The calibration uncertainty is
less than 10% in magnitude and 10 degrees in phase across the relevant
frequency band 20 Hz to 1 kHz.