Calibration of advanced Virgo and reconstruction of the detector strain h(t) during the observing run O3

Abstract

The three advanced Virgo and LIGO gravitational wave detectors participated to the third observing run (O3) between 1 April 2019 15:00 UTC and 27 March 2020 17:00 UTC, leading to several gravitational wave detections per month. This paper describes the advanced Virgo detector calibration and the reconstruction of the detector strain h(t) during O3, as well as the estimation of the associated uncertainties. For the first time, the photon calibration technique as been used as reference for Virgo calibration, which allowed to cross-calibrate the strain amplitude of the Virgo and LIGO detectors. The previous reference, so-called free swinging Michelson technique, has still been used but as an independent cross-check. h(t) reconstruction and noise subtraction were processed online, with good enough quality to prevent the need for offline reprocessing, except for the two last weeks of September 2019. The uncertainties for the reconstructed h(t) strain, estimated in this paper in a 20–2000 Hz frequency band, are frequency independent: 5% in amplitude, 35 mrad in phase and 10 μs in timing, with the exception of larger uncertainties around 50 Hz.

Detector Characterization and Mitigation of Noise in Ground-Based Gravitational-Wave Interferometers

“…The sources of the subtracted noise included laser frequency noise, scattered light noise, and amplitude noise from the laser modulation frequency. This noise subtraction improved the sensitivity by up to 7 Mpc [136].…”

“…Noise subtraction of broadband sources of noise was also used with Virgo data in the third observing run. Noise subtraction with Virgo data used similar procedures to those used with LIGO data [135,136]. The sources of the subtracted noise included laser frequency noise, scattered light noise, and amplitude noise from the laser modulation frequency.…”

Stochastic Gravitational-Wave Backgrounds: Current Detection Efforts and Future Prospects

“…Black hole binaries in particular are a vast category of sources, as the mass of each black hole in the binary ranges between 5 and 10 10 M . The lower mass of 5M here refers to the lack of black holes between the Tolman-Oppenheimer-Volkoff limit (which sets the maximum mass of a neutron star to 2.9M [57]) and 5M , as seen in low-mass X-ray binary observations [58,59] 4 . Specifically, a BH is considered massive (M BH ∼ 10 5 -10 10 M ), intermediate (M BH ∼ 10 2 -10 5 M ), and stellar mass (M BH ∼ 5-10 2 M ) [61].…”

“…In laying out stochastic background detection techniques, we focus on three categories of detectors: ground-based detector networks, pulsar timing arrays (PTAs) monitored by radio telescopes, and spaceborne detectors comprised of sets of satellites. We do not discuss in detail the impressive work on data acquisition and processing necessary to put the data in the form required for the implementation of the searches we report (see Sections 4 and 5); we refer the reader to several other papers that delineate these efforts (see, e.g., [1][2][3][4][5] for recent discussions of ground-based laser interferometer detector characterization and calibration and [6][7][8] for reviews of PTA experiments).…”

Stochastic Gravitational-Wave Backgrounds: Current Detection Efforts and Future Prospects

“…In laying out stochastic background detection techniques, we focus on three categories of detectors: ground-based detector networks, pulsar timing arrays (PTAs) monitored by radio telescopes, and spaceborne detectors comprised of sets of satellites. We do not discuss in detail the impressive work on data acquisition and processing necessary to put the data in the form required for the implementation of the searches we report (see Sections 4 and 5); we refer the reader to several other papers that delineate these efforts (see, e.g., [1][2][3][4][5] for recent discussions of ground-based laser interferometer detector characterization and calibration and [6][7][8] for reviews of PTA experiments).…”