Detection of the Displacement Gravitational Memory Effect of LIGO Binaries in the LISA Data Stream Using a Time-Domain Data Stacking Algorithm

The displacement gravitational-wave (GW) memory effect is a result of the nonlinear nature of general relativity. It predicts a permanent displacement between the reference test masses of a GW detector after the passage of a GW signal. The GW memory of individual compact binary coalescences (CBCs) is orders of magnitude below the detector background noise, which necessitates the use of coherent data stacking algorithms to yield a cumulative memory Signal-to-Noise Ratio (SNR) statistic. The Laser Interferometer Space Antenna (LISA) will be well-suited to detect the GW memory of CBCs in the LISA and LIGO bands due to gigameter arm lengths and sensitivity in the millihertz frequency band. Third-generation (3G) ground-based detectors like Cosmic Explorer (CE) and Einstein Telescope, which are scheduled to operate concurrently with LISA, improve the prospects of detecting GW memory.

We use simulated ground-based detector network triggers using source populations from the CE MPSAC dataset and search for corresponding memory strains in the LISA data stream. Improving on the time-domain stacking algorithm used by S. Ghosh et al. (2023), we now estimate that a 0.5-year coincident detector runtime with LISA and 3G ground-based detectors will be sufficient to accumulate a GW memory SNR of 5.