BinaryGFH-v2: Improved method to search for gravitational waves from sub-solar-mass, ultra-compact binaries using the Generalized Frequency-Hough Transform

TL;DR

This paper introduces BinaryGFH-v2, an enhanced pattern-recognition method using the Generalized Frequency-Hough Transform to detect gravitational waves from sub-solar-mass, ultra-compact binaries, filling a previously unexplored mass gap.

Contribution

The paper develops BinaryGFH-v2, a modified pattern-recognition technique capable of detecting rapidly spinning-up binaries in a mass range previously inaccessible to gravitational-wave searches.

Findings

Method can detect sub-solar-mass, ultra-compact binaries.

Projected constraints on primordial black hole dark matter fraction.

Enhanced sensitivity over previous approaches.

Abstract

Observing gravitational waves from sub-solar-mass, inspiraling compact binaries would provide almost smoking-gun evidence for primordial black holes. Here, we develop a method to search for ultra-compact binaries with chirp masses ranging from $[10^{-2},10^{-1}]M_\odot$. This mass range represents a previously unexplored gap in gravitational-wave searches for compact binaries: it was thought that the signals would too long for matched-filtering analyses but too short for time-frequency pattern-recognition techniques. Despite this, we show that a pattern-recognition technique, the Generalized frequency-Hough (GFH), can be employed with particular modifications that allow us to handle rapidly spinning-up binaries and to increase the statistical robustness of our method, and call this improved method BinaryGFH-v2. We then design a hypothetical search for binaries in this mass regime, compare the empirical and theoretical sensitivities of this method, and project constraints on formation rate densities and the fraction of dark matter that primordial black holes could compose in both current- and future-generation gravitational-wave detectors. Our results show that our method can be used to search for sub-solar-mass, ultra-compact objects in a mass regime that remains to-date unconstrained with gravitational waves.