Subtraction of correlated noise in global networks of gravitational-wave interferometers

Abstract

The recent discovery of merging black holes suggests that a stochastic gravitational-wave background is within reach of the advanced detector network operating at design sensitivity. However, correlated magnetic noise from Schumann resonances threatens to contaminate observation of a stochastic background. In this paper, we report on the first effort to eliminate intercontinental correlated noise from Schumann resonances using Wiener filtering. Using magnetometers as proxies for gravitational-wave detectors, we demonstrate as much as a factor of two reduction in the coherence between magnetometers on different continents. While much work remains to be done, our results constitute a proof-of-principle and motivate follow-up studies with a dedicated array of magnetometers. PACS numbers:Introduction. A stochastic gravitational-wave background (SGWB) is a potential signal source for groundbased, second-generation interferometric gravitationalwave detectors such as Advanced LIGO [1] and Advanced Virgo [2]. An astrophysical SGWB could be produced by objects such as compact binary coalescences, pulsars, magnetars, or core-collapse supernovae. A cosmological background could be generated by various physical processes in the early universe [3,4]. Previous analyses have achieved interesting constraints on these processes [3][4][5]. In particular, with the recent discovery of a binary blackhole merger [6], there is a chance of observing a SGWB from these systems [7].

Measurement and subtraction of Schumann resonances at gravitational-wave interferometers

“…about 0.6 for the dominant harmonic. This is similar to what was achieved from the last data set [14]. The middle of Fig.…”

“…We then determine the level of reduction of correlated noise in two magnetometers, which is important for SGWB searches. We made an attempt at global magnetometer subtraction in [14], predominantly using previously deployed magnetometers to construct a toy-model gravitational-wave network. In this analysis, with the previously deployed magnetometers and dedicated on-site measurements, we provide results we can expect for on-site magnetometer based subtraction with a realistic network of magnetometers.…”

“…In our previous study [14], we argued that it would be beneficial to measure the coherence between quiet magnetometers stationed near gravitational-wave detectors. In this analysis, we use these magnetometers, in addition to dedicated measurements at the gravitational-wave detectors, to perform subtraction of correlated magnetic noise in the presence of realistic levels of local magnetic noise in gravitational-wave detectors.…”

“…In previous work, we carried out a demonstration of Wiener filtering with a goal of reducing the coherence between widely separated magnetometers (serving as proxies for gravitational-wave detectors) [14]. We used previously deployed magnetometers, which allowed us access to instruments with superb sensitivity, located in very magnetically quiet locations.…”

Impact of correlated magnetic noise on the detection of stochastic gravitational waves: Estimation based on a simple analytical model

“…Subtraction and mitigation of the correlated noise is therefore very important issue, and combining the geophysical data monitored outside the GW detectors, a more efficient methodology needs to be developed, together with the experimental efforts on reducing the coupling with magnetic fields (see e.g., Refs. [20,21] along this direction).…”