Blind-search constraints on the sub-kiloparsec population of continuous gravitational-wave sources

TL;DR

This paper estimates the current and future constraints on the population of unknown neutron stars emitting continuous gravitational waves within 1 kiloparsec, highlighting the capabilities of existing and upcoming detectors to detect sources with specific ellipticities.

Contribution

It extends previous analyses to forecast the sensitivity of future gravitational-wave detectors to unknown neutron star populations based on ellipticity constraints.

Findings

Current detectors can constrain ellipticities > 10^{-7}

Third-generation detectors will improve constraints to ellipticities > 10^{-8}

Sources with ellipticity < 10^{-8} are unlikely to be constrained below 1 kHz

Abstract

We use the latest all-sky continuous gravitational-wave (CW) searches to estimate constraints on the sub-kiloparsec population of unknown neutron stars (NS). We then extend this analysis to the forthcoming LIGO-Virgo-KAGRA observing runs and the third generation (3G) of ground-based interferometric detectors (Einstein Telescope and Cosmic Explorer). We find that sources with ellipticities greater than $\epsilon \gtrsim 10^{-7}$ can be well-constrained by current and future detectors regardless of their frequency. 3G detectors will extend these constraints down to $\epsilon \gtrsim 10^{-8}$ across the whole sensitive band and $\epsilon \gtrsim 10^{-9}$ above $1\,\textrm{kHz}$. We do not expect $\epsilon \lesssim 10^{-8}$ sources to be constrained below $1\,\textrm{kHz}$. Finally, we discuss the potential impact of using astronomical priors on all-sky searches in terms of sensitivity and computing cost. The populations here described can be used as a guide to set up future all-sky CW searches.