A study on waveform requirements for the LISA space mission with current inspiral-merger-ringdown models

Abstract

[eng] The first detection of gravitational waves (GWs) in 2015 [1] marked the beginning of an ongoing revolution in astronomy and fundamental physics. Since then around 90 signals have been detected as having astrophysical origin in the three observing runs O1-O3 [2–5] and the just-started O4 [6]. After this current run, the international detector network will receive further upgrades such as ESA’s LISA mission [7, 8], scheduled for launch in the 2030s. One of the fundamental fields in GW data analysis is the estimation of the source parameters using Bayesian inference, where theoretical waveform models are used as templates for the incoming signals. Those models have achieved high accuracy with current LIGOVirgo-KAGRA detectors; however, further improvements will be required to match future detectors’ sensitivities. In this work, I test current Inspiral-Merger-Ringdown (IMR) waveforms against the LISA space mission scientific requirements [9] for massive black hole binaries (MBHB). These requirements set an upper bound on the permissible errors for parameter estimation (PE) and become a challenge for theoretical models. Apart from calibration inaccuracies of the detectors, the error has two main contributions: waveform systematics and the statistical error of the measurement. The former is estimated by computing the mismatch between the model and another one which is considered the template; whilst the statistical error can be quickly estimated with the Fisher Information Matrix approach. Then, they are compared with the observational requirements. Furthermore, in some cases, a full PE run is performed in order to check the consistency of the previous error estimates. Our purpose is to guide future waveform modeling tasks and black hole numerical simulations in order to improve current IMR models for future observing periods.