The impact of dark matter on tidal signatures in neutron star mergers with Einstein Telescope

TL;DR

This study assesses how dark matter within neutron stars affects gravitational-wave signals and explores whether future detectors like the Einstein Telescope can detect or constrain dark matter properties through neutron star merger observations.

Contribution

It introduces a Bayesian framework to analyze the impact of fermionic dark matter on neutron star mergers and evaluates the detectability of dark matter effects with next-generation gravitational-wave observatories.

Findings

Ignoring dark matter biases EOS estimates towards softer models.

ET alone is unlikely to detect dark matter effects in neutron star mergers.

Constraints on dark matter particle mass are weak due to parameter degeneracies.

Abstract

If dark matter (DM) accumulates inside neutron stars (NS), it changes their internal structure and causes a shift of the tidal deformability from the value predicted by the dense-matter equation of state (EOS). In principle, this shift could be observable in the gravitational-wave (GW) signal of binary neutron star (BNS) mergers. We investigate the effect of fermionic, non-interacting DM when observing a large number of GW events from DM-admixed BNSs with the precision of the proposed Einstein telescope (ET). Specifically, we study the impact on the recovery of the baryonic EOS and whether DM properties can be constrained. For this purpose, we create event catalogues of BNS mock events with DM fraction up to 1%, from which we reconstruct the posterior uncertainties with the Fisher matrix approach. Using this data, we perform joint Bayesian inference on the baryonic EOS, DM particle mass, and DM particle fraction in each event. Our results reveal that when falsely ignoring DM effects, the EOS posterior is biased towards softer EOSs, though the offset is rather small. Further, we find that within our assumptions of our DM model and population, ET will likely not be able to test the presence of DM in BNSs, even when combining many events and adding Cosmic Explorer (CE) to the next-generation detector network. Likewise, the potential constraints on the DM particle mass will remain weak because of degeneracies with the fraction and EOS.