All-sky search for continuous gravitational waves from isolated neutron stars in the early O3 LIGO data

Abstract

We report on an all-sky search for continuous gravitational waves in the frequency band 20-2000 Hz and with a frequency time derivative in the range of ½−1.0; þ0.1 × 10 −8 Hz=s. Such a signal could be produced by a nearby, spinning and slightly nonaxisymmetric isolated neutron star in our Galaxy. This search uses the LIGO data from the first six months of Advanced LIGO's and Advanced Virgo's third observational run, O3. No periodic gravitational wave signals are observed, and 95% confidence-level (C.L.) frequentist upper limits are placed on their strengths. The lowest upper limits on worst-case (linearly polarized) strain amplitude h 0 are ∼1.7 × 10 −25 near 200 Hz. For a circularly polarized source (most favorable orientation), the lowest upper limits are ∼6.3 × 10 −26 . These strict frequentist upper limits refer to all sky locations and the entire range of frequency derivative values. For a populationaveraged ensemble of sky locations and stellar orientations, the lowest 95% C.L. upper limits on the strain amplitude are ∼1.4 × 10 −25 . These upper limits improve upon our previously published all-sky results, with the greatest improvement (factor of ∼2) seen at higher frequencies, in part because quantum squeezing has dramatically improved the detector noise level relative to the second observational run, O2. These limits are the most constraining to date over most of the parameter space searched.

All-sky search for gravitational wave emission from scalar boson clouds around spinning black holes in LIGO O3 data

“…Fig. 4 of [50], shows that our conservative results are better than most of the past searches, including the recent early O3 analysis [50]. In particular, our minimum upper limit value improves upon that in [50] by ∼ 30%.…”

Calibration Uncertainty's Impact on Gravitational-Wave Observations

“…GW astrophysics has rapidly grown over the last few years with an ever increasing number of confidently detected compact binary coalescences [27][28][29][30] and steadily improved upper limits on the rates of other sources (see, e.g., [53,54]). This has been enabled in no small part by the remarkable understanding of the current interferometers' responses to astrophysical strain.…”

Search Methods for Continuous Gravitational-Wave Signals from Unknown Sources in the Advanced-Detector Era

“…We present a review of methods and pipelines employed to date to search for CW signals from unknown sources during the era of the advanced detectors. Specifically, we consider three kinds of searches for unknown sources: (i) blind searches, with weak prior assumptions about possible source parameters [40][41][42][43][44][45][46][47][48][49][50][51][52][53][54]; (ii) spot-light searches, focused at sky regions harbouring an interesting population of objects whose exact frequency is unknown, such as globular clusters or the Galactic Center (GC) [55,56]; and (iii) directed searches, targeting specific celestial objects compatible with a CW source, such as supernova remnants (SNRs) or low-mass X-ray binaries (LMXBs) [57][58][59][60][61][62][63][64][65][66][67][68][69].…”

“…The PowerFlux pipeline [109][110][111][112] estimates power from a CW source depending on its sky position. The basic implementation [41,42,54] uses a diagonal kernel K to combine Fourier power from each SFT. In this case, the role of K is to diminish the contribution of unfavourable frequency bins (due to high noise floors or a low antenna-pattern response) to the total weighted Fourier power.…”

“…As their names suggest, FDM looks for a CW candidate in a new dataset containing brand new information; RDM, on the other hand, re-analyses the same dataset using a different method. The typical example of FDM is to look for a CW candidate obtained in a certain observing run using data from subsequent observing runs [40,54,62]. Examples of RMD include, for example, multi-stage semicoherent or loosely coherent searches aiming towards a fully coherent search in a restricted parameter space region [36][37][38][39].…”