Detecting intermediate-mass black hole binaries with atom interferometer observatories: Using the resonant mode for the merger phase

Abstract

Atom interferometry detectors like AION, ZAIGA, and AEDGE will be able to detect gravitational waves (GWs) at dHz covering the band between large space-based laser interferometers LISA/TianQin/Taiji and ground-based facilities LIGO/Virgo/KAGRA. They will detect the late inspiral and merger of GW sources containing intermediate-mass black holes (IMBHs) in the mass range 102−105 M⊙. We study how accurately the parameters of an IMBH binary can be measured using AION's power spectral density. Furthermore, we propose a detection scheme where the early inspiral of the binary is detected using the regular broadband mode while the merger is detected using the resonant mode. We find that using such a detection scheme, the signal-to-noise ratio of the detection and the detection accuracy of the parameters can be enhanced compared to the full detection of the signal using the broadband mode. We, further, assess the impact of the necessary detection gap while switching from broadband to resonant mode studying the case of a short (30 s) and a long (600 s) gap. We find that the improvement in the detection accuracy for both gaps is around 40% for the total mass and the spin of the heavier black hole. For the short gap, the accuracy always improves ranging between 2% and 31% for the other parameters. For the long gap, there is a decrease in the detection accuracy for the luminosity distance, the inclination, and the initial phase but only by 1%–6% while for the remaining parameters, we have improved accuracies of around 2%–20%.