Line-robust statistics for continuous gravitational waves: safety in the case of unequal detector sensitivities

TL;DR

This paper evaluates the safety and effectiveness of line-robust detection statistics for continuous gravitational waves when detectors have unequal sensitivities, confirming their robustness in most practical scenarios.

Contribution

It extends previous line-robust statistics analysis to cases with unequal detector sensitivities and assesses their safety and performance boundaries.

Findings

Line-robust statistics remain safe with unequal sensitivities in most practical cases.

Optimal tuning of the original statistic ensures robustness against false alarms.

Proposed improvements have limited practical benefit.

Abstract

The multi-detector F-statistic is close to optimal for detecting continuous gravitational waves (CWs) in Gaussian noise. However, it is susceptible to false alarms from instrumental artefacts, for example quasi-monochromatic disturbances ('lines'), which resemble a CW signal more than Gaussian noise. In a recent paper [Keitel et al 2014, PRD 89 064023], a Bayesian model selection approach was used to derive line-robust detection statistics for CW signals, generalising both the F-statistic and the F-statistic consistency veto technique and yielding improved performance in line-affected data. Here we investigate a generalisation of the assumptions made in that paper: if a CW analysis uses data from two or more detectors with very different sensitivities, the line-robust statistics could be less effective. We investigate the boundaries within which they are still safe to use, in comparison with the F-statistic. Tests using synthetic draws show that the optimally-tuned version of the original line-robust statistic remains safe in most cases of practical interest. We also explore a simple idea on further improving the detection power and safety of these statistics, which we however find to be of limited practical use.