Description
Current LIGO-Virgo-KAGRA modeled searches for gravitational waves emitted by compact binary coalescences treat binary neutron star and neutron star-black hole sources as point-particle systems, ignoring the influence of the internal neutron star physics. The main finite-size effects are due to tidal deformations of neutron stars induced by the gravitational coupling in the binary. Such effects are quantified by the tidal deformability of neutron stars in the system, which strongly depends on the equation of state model assumed.
Technically speaking, this means that template banks against which detector data are matched filtered are built with point-particle waveform models (templates). However, finite-size effects are small, but not negligible, ignoring them causes a loss in search sensitivity.
We demonstrate this considering the template bank currently used by the PyCBC search in the fourth LIGO-Virgo-KAGRA observing run. We assessed its validity against different sets of putative signals (injections): BNS injections with non-zero tidal deformabilities lead to a performance of the bank worse than that against point-particle injections. Consequently we propose a new strategy to account for tidal deformabilities in the construction of binary neutron star template banks: we extract tidal deformability values according to a prior informed by the constraints on the neutron star equation of state provided by the observation of GW170817. We present the results of building a binary neutron star template bank with such approach. Compared to an equivalent bank built with point-particle templates, we obtain better performances against injections with non-zero tidal deformabilities, as well as only 10% of extra templates.
