The Continuous Wave Group is a joint working group of the LIGO Scientific Collaboration (LSC), Virgo Collaboration, and KAGRA Collaboration, and is tasked with searching for the signatures of continuous gravitational waves in data from the LIGO, Virgo, and KAGRA gravitational wave detectors.
We carry out searches for continuous gravitational waves targeted at known astronomical objects: pulsars such as the Crab pulsar, lowmass Xray binaries such as Scorpius X1, and supernova remnants such as Cassiopeia A.
We also perform allsky surveys for asyet unknown sources. These could be rapidlyspinning neutron stars in our Galaxy which radiate continuous gravitational waves, but are not visible in the electromagnetic spectrum. Or they could be the exotic signatures of dark matter.
This table lists all scientific publications produced (to date) by the Continuous Wave Group and authored by the LSC, Virgo, and KAGRA Collaborations.
Gravitational waves have been detected by the LIGO (Laser Interferometer Gravitationalwave Observatory) and Virgo interferometric detectors. The gravitational wave events detected thus far have been from the collision and merger of two black holes (e.g. GW150914), or two neutron stars (e.g. GW170817). The detectable signatures of events of this type are typically very short, lasting from much less than a second to a few minutes.
Continuous gravitational waves are a different, hypothesised class of gravitational waves which have so far not been detected. Unlike the shortlived chirp events from binary black holes and binary neutron stars, continuous gravitational waves are expected to be always present, like a background humming sound, in the gravitational wave detectors. See here for illustrations and an example sound bite of such signals.
The most likely sources of continuous gravitational waves are spinning neutron stars in our Galaxy. A small bump on the star's surface a few millimetres in height, or a slight wobble in its rotation, could generate gravitational disturbances that would be detectable as gravitational waves here on Earth. These waves would, however, be much weaker than those generated by binary black hole or binary neutron star collisions, which makes them much more challenging to detect.
The youngest neutron stars which could be radiating continuous gravitational waves are likely to be hundreds of years old, if not much older. However, it is also possible that a very young neutron star — born in the collision and merger of two neutron stars — may also radiate continuous gravitational waves for a short period of time.
A detailed review article about sources, search methods and results is arXiv:2206.06447 (Riles 2022).
In searching for continuous gravitational wave sources, we must make corrections for the intrinsic change in the frequency of the waves over time, the Earth's rotation and orbital motion around the Sun, and in some cases the motion of the source itself if it is in orbit around a companion star. As the timespan of the data being analysed increases, these corrections become very computationally challenging to perform when all or some of the parameters of the source (e.g. its sky position and intrinsic frequency) are not known a priori. For example, an allsky survey for sources spinning at detectable frequencies, if carried out using the most sensitive search algorithm, would easily exhaust the capability of all computers in existence! For these kinds of searches, we must therefore make use of different algorithms which are not the most sensitive, but are computationally cheap enough to run on modern supercomputers.
This table lists all scientific publications produced (to date) by the Continuous Wave Group and authored by the LSC, Virgo, and KAGRA Collaborations. For quick summaries of each of the more recent publications, click the "summary" links.
Publications from the most recent completed observing run (O3) are:
Modelbased crosscorrelation search for gravitational waves from the lowmass Xray binary Scorpius X1 in LIGO O3 data [ApJL941:L30 (2022) / arXiv:2209.02863]

Search for continuous gravitational wave emission from the Milky Way center in O3 LIGOVirgo data [PRD106.042003 (2022) / arXiv:2204.04523]

Search for gravitational waves from Scorpius X1 with a hidden Markov model in O3 LIGO data [PRD106,062002 (2022) / arXiv:2201.10104]

Allsky search for continuous gravitational waves from isolated neutron stars using Advanced LIGO and Advanced Virgo O3 data [PRD106.102008 (2022) / arXiv:2201.00697]

Narrowband searches for continuous and longduration transient gravitational waves from known pulsars in the LIGOVirgo third observing run [ApJ932:133 (2022) / arXiv:2112.10990]

Search of the Early O3 LIGO Data for Continuous Gravitational Waves from the Cassiopeia A and Vela Jr. Supernova Remnants [PRD105.082005 (2022) / arXiv:2111.15116]

Allsky search for gravitational wave emission from scalar boson clouds around spinning black holes in LIGO O3 data [PRD105.102001 (2022) / arXiv:2111.15507]

Searches for Gravitational Waves from Known Pulsars at Two Harmonics in the Second and Third LIGOVirgo Observing Runs [ApJ935:1 (2022) / arXiv:2111.13106]

Search for continuous gravitational waves from 20 accreting millisecond Xray pulsars in O3 LIGO data [PRD105.022002 (2022) / arXiv:2109.09255]

Allsky search for continuous gravitational waves from isolated neutron stars in the Early O3 LIGO Data [PRD104.082004 (2021) / arXiv:2107.00600]

Constraints on dark photon dark matter using data from LIGO's and Virgo's third observing run [PRD105.063030 (2022) / arXiv:2105.13085]

Searches for continuous gravitational waves from young supernova remnants in the early third observing run of Advanced LIGO and Virgo [ApJ921:80 (2021) / arXiv:2105.11641]

Constraints from LIGO O3 data on gravitationalwave emission due to rmodes in the glitching pulsar PSR J05376910 [ApJ922:71 (2021) / arXiv:2104.14417]

Diving below the spindown limit: Constraints on gravitational waves from the energetic young pulsar PSR J05376910 [ApJL913:L27 (2021) / arXiv:2012.12926]

Allsky search in early O3 LIGO data for continuous gravitationalwave signals from unknown neutron stars in binary systems [PRD103,064017 (2021) / arXiv:2012.12128 ]

Gravitationalwave constraints on the equatorial ellipticity of millisecond pulsars [ApJL902:L21 (2020) / arXiv:2007.14251]

This is a list of workshops with a focus on the science of continuous gravitational waves. Several of these workshops were organised by the Continuous Wave Group to provide a forum for discussion with neutron star experts, in order to ensure that our searches are guided by the latest observational results and theoretical findings. Other workshops were independently organised with the involvement of Continuous Wave Group members.