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Abstract As the Advanced LIGO and Advanced Virgo interferometers, soon to be joined by the KAGRA interferometer, increase their sensitivity, they detect an ever-larger number of gravitational waves with a significant presence of higher multipoles (HMs) in addition to the dominant (2, 2) multipole. These HMs can be detected with different approaches, such as the minimally-modeled burst search methods, and here we discuss one such approach based on the coherent WaveBurst (cWB) pipeline. During the inspiral phase the HMs produce chirps whose instantaneous frequency is a multiple of the dominant (2, 2) multipole, and here we describe how cWB can be used to detect these spectral features. The search is performed within suitable regions of the time-frequency representation; their shape is determined by optimizing the receiver operating characteristics. This novel method has already been used in the GW190814 discovery paper (Abbott et al 2020 Astrophys. J. Lett. 896 L44) and is very fast and flexible. Here we describe in full detail the procedure used to detect the (3, 3) multipole in GW190814 as well as searches for other HMs during the inspiral phase, and apply it to another event that displays HMs, GW190412, replicating the results obtained with different methods. The procedure described here can be used for the fast analysis of HMs and to support the findings obtained with the model-based Bayesian parameter estimates.
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Improving LIGO calibration accuracy by using time-dependent filters to compensate for temporal variations
Abstract The response of the Advanced Laser Interferometer Gravitational-wave Observatory (Advanced LIGO) interferometers is known to vary with time (Tuyenbayev et al 2017 Class. Quantum Grav. 34 015002). Accurate calibration of the interferometers must therefore track and compensate for temporal variations in calibration model parameters. These variations were tracked during the first three Advanced LIGO observing runs, and compensation for some of them has been implemented in the calibration procedure. During the second observing run, multiplicative corrections to the interferometer response were applied while producing calibrated strain data both in real time and in high latency. In a high-latency calibration produced after the second observing run and during the entirety of the third observing run, a correction requiring periodic filter updates was applied to the calibration–the time dependence of the coupled cavity pole frequency f c c . This paper describes the methods developed to compensate for variations in the interferometer response requiring time-dependent filters, including variable zeros, poles, gains, and time delays. The described methods were used to provide compensation for well-modeled time dependence of the interferometer response, which has helped to reduce systematic errors in the calibration to < 2% in magnitude and < 2 ∘ in phase across LIGO’s most sensitive frequency band of 20–2000 Hz (Sun et al 2020 Class. Quantum Grav. 37 225008; Sun et al 2021 arXiv:2107.00129 [astro-ph.IM]). Additionally, this paper shows how such compensation is relevant for astrophysical inference studies by reducing uncertainty and bias in the sky localization for a simulated binary neutron star merger.
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- PAR ID:
- 10394276
- Date Published:
- Journal Name:
- Classical and Quantum Gravity
- Volume:
- 40
- Issue:
- 3
- ISSN:
- 0264-9381
- Page Range / eLocation ID:
- 035001
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1088/1361-6382/acabf6
