Search for continuous gravitational waves: Improving robustness versus instrumental artifacts

Abstract

The standard multidetector F-statistic for continuous gravitational waves is susceptible to false alarms from instrumental artifacts, for example monochromatic sinusoidal disturbances ("lines"). This vulnerability to line artifacts arises because the F-statistic compares the signal hypothesis to a Gaussian-noise hypothesis, and hence is triggered by anything that resembles the signal hypothesis more than Gaussian noise. Various ad-hoc veto methods to deal with such line artifacts have been proposed and used in the past. Here we develop a Bayesian framework that includes an explicit alternative hypothesis to model disturbed data. We introduce a simple line model that defines lines as signal candidates appearing only in one detector. This allows us to explicitly compute the odds between the signal hypothesis and an extended noise hypothesis, resulting in a new detection statistic that is more robust to instrumental artifacts. We present and discuss results from Monte-Carlo tests on both simulated data and on detector data from the fifth LIGO science run. We find that the line-robust statistic retains the detection power of the standard F-statistic in Gaussian noise. In the presence of line artifacts it is more sensitive, even compared to the popular F-statistic consistency veto, over which it improves by as much as a factor of two in detectable signal strength.

First low-frequency Einstein@Home all-sky search for continuous gravitational waves in Advanced LIGO data

“…According to Eq. (67) of [30], with N seg ¼ 12 this 2F value corresponds to a Gaussian false-alarm probability of 10 −9 . Furthermore, we assume equal-odds priors between the various noise hypotheses ("L" for line, "G" for Gaussian, "tL" for transient line).…”

“…We use a different ranking statistic from the original search, because with 2 segments the transient line veto is not useful. Instead we use the ranking statisticβ S=GL ≔ log 10BS=GL , introduced in [30] and previously used in [3], with tunings updated for N seg ¼ 2.…”

Comparison of methods for the detection of gravitational waves from unknown neutron stars

“…The 2F at the closest coarse grid point in each segment is summed to approximate the average 2F at a given fine grid point across the entire data set. The logBSGL statistic, described in [20], is calculated for each fine-grid point. This is derived from the 2F -statistic, and suppresses detector artifacts appearing in one detector.…”

Hierarchical follow-up of subthreshold candidates of an all-sky Einstein@Home search for continuous gravitational waves on LIGO sixth science run data

“…We fix the total run time to be 4 months on Einstein@Home, and this yields an optimal search set-up having the same coherent time baseline as stage 0, 60 h, with the same number of segments N seg ¼ 90 and the grid spacings shown in Table I. We use the same ranking statistic as in the original search [5], theÔ SGL [11], with the same tunings (c à and normalized short Fourier transform power threshold). The 90% uncertainty regions for this search setup for signals just above the detection threshold are 8 > < > :…”