Waveform systematics for binary neutron star gravitational wave signals: effects of the point-particle baseline and tidal descriptions

TL;DR

This paper investigates systematic biases in gravitational wave data analysis for binary neutron star mergers, highlighting significant discrepancies in tidal parameter estimation due to waveform model choices, emphasizing the need for improved models.

Contribution

The study compares different waveform models for neutron star mergers, revealing biases in tidal parameter extraction and emphasizing the necessity for more accurate waveform models.

Findings

Mass and spin estimates are robust across models.

Tidal deformability estimates vary significantly between models.

Higher Post-Newtonian order does not monotonically improve estimates.

Abstract

Gravitational wave (GW) astronomy has consolidated its role as a new observational window to reveal the properties of compact binaries in the Universe. In particular, the discovery of the first binary neutron star coalescence, GW170817, led to a number of scientific breakthroughs as the possibility to place constraints on the equation of state of cold matter at supranuclear densities. These constraints and all scientific results based on them require accurate models describing the GW signal to extract the source properties from the measured signal. In this article, we study potential systematic biases during the extraction of source parameters using different descriptions for both, the point-particle dynamics and tidal effects. We find that for the considered cases the mass and spin recovery show almost no systematic bias with respect to the chosen waveform model. However, the extracted tidal effects can be strongly biased, where we find generally that Post-Newtonian approximants predict neutron stars with larger deformability and radii than numerical relativity tuned models. Noteworthy, an increase in the Post-Newtonian order in the tidal phasing does not lead to a monotonic change in the estimated properties. We find that for a signal with strength similar to GW170817, but observed with design sensitivity, the estimated tidal parameters can differ by more than a factor of two depending on the employed tidal description of the waveform approximant. This shows the current need for the development of better waveform models to extract reliably the source properties from upcoming GW detections.