A semi-coherent analysis method to search for continuous gravitational waves emitted by ultra-light boson clouds around spinning black holes

TL;DR

This paper introduces a computationally efficient analysis pipeline for detecting continuous gravitational waves from ultra-light boson clouds around black holes, accounting for slight frequency variations and other sources.

Contribution

It presents a novel, robust, and low-cost data analysis method tailored for broad classes of persistent gravitational wave signals, including those with wandering phases.

Findings

The pipeline is theoretically sensitive to targeted signals.

Synthetic data analysis confirms the method's effectiveness.

Applicable to all-sky and directed searches.

Abstract

As a consequence of superradiant instability induced in Kerr black holes, ultra-light boson clouds can be a source of persistent gravitational waves, potentially detectable by current and future gravitational-wave detectors. These signals have been predicted to be nearly monochromatic, with a small steady frequency increase (spin-up), but given the several assumptions and simplifications done at theoretical level, it is wise to consider, from the data analysis point of view, a broader class of gravitational signals in which the phase (or the frequency) slightly wander in time. Also other types of sources, e.g. neutron stars in which a torque balance equilibrium exists between matter accretion and emission of persistent gravitational waves, would fit in this category. In this paper we present a robust and computationally cheap analysis pipeline devoted to the search of such kind of signals. We provide a full characterization of the method, through both a theoretical sensitivity estimation and through the analysis of syntethic data in which simulated signals have been injected. The search setup for both all-sky searches and higher sensitivity directed searches is discussed.