Detection of Gravitational memory effect in LISA using triggers from ground-based detectors.

The LIGO-Virgo-Kagra (LVK) collaboration has detected gravitational waves from 90 Compact Binary Coalescences. In addition to fortifying the linearized theory of General Relativity (GR), the statistical ensemble of detections provides information on the astrophysics of the binary sources and prospects detect nonlinear effects predicted by GR. One such prediction is the effect of nonlinear gravitational memory, which is a permanent strain in space-time after the passage of the gravitational wave. For compact binary sources, the memory strain from individual detectors is about a couple of orders below the noise background. This fact motivates the idea of coherently stacking up data streams from recorded GW events so that the cumulative memory strain is detected with a high SNR. Additionally, since most of the energy is radiated at merger the strain induced by the memory effect resembles a step function at the merger time, thus making the stacking scheme much simpler (as opposed to stacking oscillating GW waveforms). Moreover, since the GW detectors essentially record the integrated strain response, the use of long arm interferometers is ideal to detect the memory effect at low frequency. LISA (Laser Interferometer Space Antenna) is a future space-based GW detector with arms oriented in an approximate equilateral triangle of length 2.5 Gm, sensitive in the 0.1 mHz to 1 Hz frequency range. In this talk, we propose a method which is designed to use the event catalog of ground-based detectors and search for corresponding memory strains in the LISA data stream. Additionally, given the LVK catalog and assuming certain source population models, we use scaling arguments to conservatively estimate the run time required for LISA to accumulate a memory SNR of 5, using triggers from future ground-based detectors. Finally, we extend these calculations for using beyond LISA missions like ALIA, AMIGO and FOLKNER to detect the gravitational memory effect. The results for LISA predict a detection of the memory effect within the 10 years lifetime while the corresponding results for beyond LISA missions are even more promising