Implementation of a new weave-based search pipeline for continuous gravitational waves from known binary systems

Abstract

Scorpius X-1 (Sco X-1) has long been considered one of the most promising targets for detecting continuous gravitational waves with ground-based detectors. Observational searches for Sco X-1 have achieved substantial sensitivity improvements in recent years, to the point of starting to rule out emission at the torque-balance limit in the low-frequency range $\ensuremath{\sim}40--180\text{ }\text{ }\mathrm{Hz}$. In order to further enhance the detection probability, however, there is still much ground to cover for the full range of plausible signal frequencies $\ensuremath{\sim}20--1500\text{ }\text{ }\mathrm{Hz}$, as well as a wider range of uncertainties in binary orbital parameters. Motivated by this challenge, we have developed binaryweave, a new search pipeline for continuous waves from a neutron star in a known binary system such as Sco X-1. This pipeline employs a semicoherent StackSlide $\mathcal{F}$-statistic using efficient lattice-based metric template banks, which can cover wide ranges in frequency and unknown orbital parameters. We present a detailed timing model and extensive injection-and-recovery simulations that illustrate that the pipeline can achieve high detection sensitivities over a significant portion of the parameter space when assuming sufficiently large (but realistic) computing budgets. Our studies further underline the need for stricter constraints on the Sco X-1 orbital parameters from electromagnetic observations, in order to be able to push sensitivity below the torque-balance limit over the entire range of possible source parameters.