Narrowband searches for continuous and long-duration transient gravitational waves from known pulsars in the LIGO-Virgo third observing run

Abstract

Isolated neutron stars that are asymmetric with respect to their spin axis are possible sources of detectable continuous gravitational waves. This paper presents a fully-coherent search for such signals from eighteen pulsars in data from LIGO and Virgo's third observing run (O3). For known pulsars, efficient and sensitive matched-filter searches can be carried out if one assumes the gravitational radiation is phase-locked to the electromagnetic emission. In the search presented here, we relax this assumption and allow the frequency and frequency time-derivative of the gravitational waves to vary in a small range around those inferred from electromagnetic observations. We find no evidence for continuous gravitational waves, and set upper limits on the strain amplitude for each target. These limits are more constraining for seven of the targets than the spin-down limit defined by ascribing all rotational energy loss to gravitational radiation. In an additional search we look in O3 data for long-duration (hours-months) transient gravitational waves in the aftermath of pulsar glitches for six targets with a total of nine glitches. We report two marginal outliers from this search, but find no clear evidence for such emission either. The resulting duration-dependent strain upper limits do not surpass indirect energy constraints for any of these targets.

Empirically estimating the distribution of the loudest candidate from a gravitational-wave search

“…No simple amendment, other than using a higher mismatch [10,53], is currently available to obtain robust results with distromax in this situation. This phenomenon was observed in [90,91], where distromax was applied to process the result of both a search for CW signals and a search for long-duration transient GWs from glitching pulsars. The CW search used a mismatch of m ≃ 0.02 combined with a toplist, which reduced the effect of such a dense parameter-space converging on the batchmax distribution.…”

Search setup for long-duration transient gravitational waves from glitching pulsars during LIGO-Virgo third observing run

“…In this contribution we have summarized the search setup and method of a search for longduration transient-CWs from pulsars that have glitched during Advanced LIGO and Advanced Virgo's third observing run. The results are reported in an LVK paper [1] which includes also the narrow-band searches for persistent CWs from a larger set of known pulsars.…”

“…Gravitational wave (GW) emission may follow these peculiar events. We give an overview of the setup for an analysis of GW data from the Advanced LIGO and Virgo third observing run (O3) [1] searching for transient GW signals lasting hours to months after glitches in known pulsars. The search method consists of placing a template grid in frequency-spindown space with fixed grid spacings.…”

Status and Perspectives of Continuous Gravitational Wave Searches

“…The latest results from the O3 fully coherent narrow-band search can be found in [240]. The search looks for CW from 18 pulsars using the five-vector and F-statistic narrow-band pipelines.…”