First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data

Abstract

Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a fully coherent search, based on matched filtering, which uses the position and rotational parameters obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto-noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have been developed, allowing a fully coherent search for gravitational waves from known pulsars over a fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of 11 pulsars using data from Advanced LIGO's first observing run. Although we have found several initial outliers, further studies show no significant evidence for the presence of a gravitational wave signal. Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for the first time. For an additional 3 targets, the median upper limit across the search bands is below the spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried out so far.

First search for long-duration transient gravitational waves after glitches in the Vela and Crab pulsars

“…The overall frequency evolution template count is N λ = N f Nḟ ≈ 1.15 × 10 7 . Comparing with [17], these choices mean we cover slightly wider ranges in f andḟ for Vela while for the Crab we cover the same f and a narrowerḟ range by a factor 15.…”

“…So far, the only dedicated analysis of LIGO-Virgo [13,14] data that touched on this topic was a search for short (∼ O(s)) signals from a 2006 glitch of the Vela pulsar in initial LIGO data [15]. Targeted searches for continuous wave (CW) signals from known pulsars (most recently [16][17][18][19]) have also taken observed glitches into account as breaks in the pulsar ephemerides, but these always focus on persistent signals lasting for the full ob- * david.keitel@ligo.org servation times before/after the glitch. Intermediateduration transient searches have also been performed on magnetar bursts (most recently in [20] and to look for a post-merger remnant of GW170817 [21,22], but for those targets the emission mechanisms and parameter space are very different than for pulsar glitches.…”

Fast and accurate sensitivity estimation for continuous-gravitational-wave searches

“…(ii) Narrow-band searches for known pulsars assume a arXiv:1808.02459v1 [gr-qc] 7 Aug 2018 small uncertainty in the relationship between CW frequency and the measured pulsar spin rates. This finite search parameter space requires a template bank with (typically) many millions of templates, still allowing for optimal fully-coherent search methods to be used [20].…”

“…The first paper [25] searched the lower frequency range [20,475] Hz, using four methods: PowerFlux, Frequency-Hough, SkyHough and a time-domain F-statistic search with segment-coincidences (denoted as F TD +Coinc). The PowerFlux, FrequencyHough and SkyHough search used SFT lengths in the range 1800 − 7200s as coherent segments while the Time-Domain F-statistic used a coherence time of T seg = 6 d. The total amount of analyzed data was about 77 d of H1 data and 66 d of L1 data.…”

Population synthesis of accreting neutron stars emitting gravitational waves

“…Rapidly-rotating NSs have been the subject of many GW searches. These include searches of known radio pulsars (Abbott et al 2004(Abbott et al , 2005b(Abbott et al , 2007a(Abbott et al , 2008b(Abbott et al , 2010(Abbott et al , 2017c(Abbott et al ,d, 2018bAbadie et al 2011a,b;Aasi et al 2014Aasi et al , 2015a, along with wide-parameter surveys for unknown pulsars (Abbott et al 2005a(Abbott et al , 2007b(Abbott et al , 2008a(Abbott et al , 2009(Abbott et al , 2016(Abbott et al , 2017b(Abbott et al , 2018aAbadie et al 2012;Aasi et al 2013). Assuming torque balance, then the brightest X-ray sources should thus be the loudest in GW emission.…”