First joint observation by the underground gravitational-wave detector, KAGRA, with GEO600

TL;DR

This paper reports the first joint observation of gravitational waves by KAGRA and GEO600, demonstrating the network's sensitivity and setting limits on detectable signals, despite no detections during the run.

Contribution

First joint observational analysis of KAGRA and GEO600 detectors, showcasing their combined capabilities for gravitational-wave detection.

Findings

No gravitational-wave events detected during the run.

Established sensitivity thresholds and spacetime volume for binary neutron-star coalescences.

Placed lower limits on distances to gamma-ray bursts based on non-detections.

Abstract

We report the results of the first joint observation of the KAGRA detector with GEO600. KAGRA is a cryogenic and underground gravitational-wave detector consisting of a laser interferometer with three-kilometer arms, and located in Kamioka, Gifu, Japan. GEO600 is a British--German laser interferometer with 600 m arms, and located near Hannover, Germany. GEO600 and KAGRA performed a joint observing run from April 7 to 20, 2020. We present the results of the joint analysis of the GEO--KAGRA data for transient gravitational-wave signals, including the coalescence of neutron-star binaries and generic unmodeled transients. We also perform dedicated searches for binary coalescence signals and generic transients associated with gamma-ray burst events observed during the joint run. No gravitational-wave events were identified. We evaluate the minimum detectable amplitude for various types of transient signals and the spacetime volume for which the network is sensitive to binary neutron-star coalescences. We also place lower limits on the distances to the gamma-ray bursts analysed based on the non-detection of an associated gravitational-wave signal for several signal models, including binary coalescences. These analyses demonstrate the feasibility and utility of KAGRA as a member of the global gravitational-wave detector network.