Ground-based interferometric gravitational-wave search refers to the use of extremely large interferometers built on the ground to passively detect (or "observe") gravitational wave events from throughout the cosmos. Most recorded gravitational wave observations have been made using this technique; the first detection, revealing the merger of two black holes, was made in 2015 by the LIGO sites.
As of 2024[update], major detectors are the two LIGO sites in the United States, Virgo in Italy and KAGRA in Japan, which are all part of the second generation of operational detectors. Developing projects include LIGO-India as part of the second generation, and the Einstein Telescope and Cosmic Explorer forming a third generation. Space-borne inteferometers such as LISA are also planned, with a similar concept but targeting different kind of sources and using very different technologies.
History
[edit]While gravitational waves were first formulated as part of general relativity by Einstein in 1916,[1] there were no real attempts to detect them until the 1960s, when Joseph Weber created the first of so-called "Weber bars". While these proved unable to reach the required sensitivity for detecting gravitational waves, many research groups focused on this topic were created at that time. While a lot of efforts were dedicated to improving the resonant bar design, the idea of using a large interferometer for gravitational wave detection was formulated in the 1970s and began to gain traction in the 1980s, leading to the foundation of LIGO in 1984 and Virgo in 1989.[2][3]
Most of the current large interferometers started construction in the 1990s and finished in the early 2000s (1999 for LIGO,[4] 2003 for Virgo,[5] 2002 for GEO 600). After a few years of observation and improvements to reach their target sensitivity, it became clear that a detection was unlikely and that further upgrades were required, leading to large projects now labelled as the "second generation of detectors" (Advanced LIGO and Virgo), with important sensitivity gains. This periods also marked the beginning of joint observing periods between the different detectors, which are crucial to confirm the validity of a signal, and sparked collaborations between the different teams.
The second generation upgrades were made during the early 2010s, lasting from 2010 to 2014 for LIGO and 2011 to 2017 for Virgo. In parallel, the KAGRA project was launched in Japan in 2010. In 2015, soon after restarting observations, the two LIGO detectors achieved the first direct observation of gravitational waves. This marked the beginning of the still ongoing series of gravitational wave observation periods, labelled O1 through O5;[6] Virgo joined the observations in 2017, near the end of the O2 period, leading quickly to the first three-detector observation, and a few days later the GW170817 event, which is the only one to date to have been observed both with gravitational waves and electromagnetic radiation. KAGRA was completed in 2020, only observing for brief periods of time due to its low sensitivity up until now.
The O4 observing run is currently ongoing, and expected to last until June 2025. More than 90 confirmed detections have been published; the collaborations now also produce live alerts when signals are detected, with more than 100 significant alerts already emitted during O4.[7]
Principle
[edit]In general relativity, a gravitational wave is a space-time perturbation which propagates at the speed of light. It thus slightly curves space-time, which locally changes the light path. Mathematically speaking, if is the amplitude (assumed to be small) of the incoming gravitational wave and the length of the optical cavity in which the light is in circulation, the change of the optical path due to the gravitational wave is given by the formula:[8]with being a geometrical factor which depends on the relative orientation between the cavity and the direction of propagation of the incoming gravitational wave. In other terms, the change in length is proportional to both to the length of the cavity and the amplitude of the gravitational wave.
Interferometer
[edit]In a typical configuration, the detector is a Michelson interferometer whose mirrors are suspended. A laser is divided into two beams by a beam splitter tilted by 45 degrees. The two beams propagate in the two perpendicular arms of the interferometer, are reflected by mirrors located at the end of the arms, and recombine on the beam splitter, generating interferences which are detected by a photodiode. An incoming gravitational wave changes the optical path of the laser beams in the arms, which then changes the interference pattern recorded by the photodiode.
This means the various mirrors of the interferometer must be "frozen" in position: when they move, the optical cavity length changes and so does the interference signal read at the instrument output port. The mirror positions relative to a reference and their alignment are monitored accurately in real time[9] with a precision better than the tenth of a nanometre for the lengths;[10] at the level of a few nano radians for the angles. The more sensitive the detector, the narrower its optimal working point. Reaching that working point from an initial configuration in which the various mirrors are moving freely is a control system challenge; a complex series of steps is required to coordinate all the steerable parts of the interferometer. Once the working point is achieved, corrections are continuously applied to keep it in the optimal configuration.[11]
The signal induced by a potential gravitational wave is thus "embedded" in the light intensity variations detected at the interferometer output.[12] Yet, several external causes—globally denoted as noise—change the interference pattern perpetually and significantly. Should nothing be done to remove or mitigate them, the expected physical signals would be buried in noise and would then remain undetectable. The design of detectors like Virgo and LIGO thus requires a detailed inventory of all noise sources which could impact the measurement, allowing a strong and continuing effort to reduce them as much as possible.[13][10]
Using an interferometer rather than a single optical cavity allows one to significantly enhance the detector's sensitivity to gravitational waves. Indeed, in this configuration based on an interference measurement, the contributions from some experimental noises are strongly reduced: instead of being proportional to the length of the single cavity, they depend in that case on the length difference between the arms (so equal arm length cancels the noise). In addition, the interferometer configuration benefits from the differential effect induced by a gravitational wave in the plane transverse to its direction of propagation: when the length of an optical path changes by a quantity , the perpendicular optical path of the same length changes by (same magnitude but opposite sign). And the interference at the output port of a Michelson interferometer depends on the difference of length between the two arms: the measured effect is hence amplified by a factor of 2 compared to a simple cavity.
The optimal working point of an interferometric detector of gravitational waves is slightly detuned from the "dark fringe", a configuration in which the two laser beams recombined on the beam splitter interfere in a destructive way: almost no light is detected at the output port.
Detectors
[edit]LIGO
[edit]LIGO is composed of two different detectors, one in Hanford, Washington and one in Livingston, Louisiana (they are thus separated by around 3000 km); the two detectors have very similar design, with 4 km long arms, although there are minor differences between the two. They were part of the first generation of detectors, and were completed in 2002; in 2010, they were shut down for an important set of upgrades, termed "Advanced LIGO", making the improved detector a part of the second generation. These upgrades were finished in early 2015, following which the two detectors made the first detection of gravitational waves.
Virgo
[edit]![](https://upload.wikimedia.org/wikipedia/commons/thumb/5/55/Virgo_aerial_view_01.jpg/220px-Virgo_aerial_view_01.jpg)
Virgo is a single detector located near Pisa, Italy, with 3 km long arms. It was part of the first generation of detectors, following its completion in 2003; it was shut down in 2011 to prepare for the "Advanced Virgo" second-generation upgrades. The upgrades were completed in 2017, allowing it to join the "O2" run, quickly making the first three-detector detection jointly with LIGO.
KAGRA
[edit]![](https://upload.wikimedia.org/wikipedia/commons/thumb/b/bc/In-construction_KAGRA_gravitational-wave_detector.jpg/220px-In-construction_KAGRA_gravitational-wave_detector.jpg)
KAGRA (formerly known as LCGT) is a single interferometer with 3 km long arms, based in the Kamioka Observatory in Japan, which is part of the second generation of detectors. It was first made operational in 2020, although it has not been able to make a detection yet. Although the base design is similar to LIGO and Virgo, it is built underground and integrates cryogenic mirrors, which is why it has often been referred to as a "2.5 generation detector".[14]
Other detectors
[edit]GEO600 was initially designed as a British-German effort to build an interferometer with 3 km long arms; it was later downscaled to 600 m due to funding reasons. It was completed in 2002 and is located near Hanover, Germany. Although it has limited capacities (especially in the lower frequency range), making a detection unlikely, it plays a key role in the gravitational wave network as a testbed for many new technologies.[15]
TAMA 300 (and its predecessor, the prototype TAMA 20) was a Japanese detector with 300 m arms, built at the Mitaka university. It was partly designed as a stepstone for larger detectors (including KAGRA), and operated between 1999 and 2004. It has now been repurposed as a testbed for new technologies.[16] The CLIO detector, with 100 m arms and located in the Kamioka mine, is another test detector, specifically designed to test the cryogenic technology used in KAGRA.[17]
LIGO-Australia is a defunct project which was envisioned to be built on the model of the LIGO detector in Australia, but was finally not funded by the Australian government; the project was later relocated to become LIGO-India.
The Fermilab Holometer, with its 39 m long arms, probes a pretty different range in frequency than other interferometers, aiming for the MHz range.
Future detectors
[edit]LIGO-India
[edit]LIGO-India is a current project of a single interferometer based in Aundha, India, following a design very similar to LIGO (with support from the LIGO collaboration). It has received approval from the Indian government in 2023, and is planned to be completed around 2030.[18]
Cosmic Explorer
[edit]Cosmic Explorer is a project for a third-generation detector, featuring two interferometers with respectively 40 km and 20 km long arms located in two different places in the United States. It relies on a design similar to LIGO, leveraging the experience from the two LIGO detectors, scaled to the much longer arm length. It is currently going through the process of approval by the NSF. If approved, it should be completed by the end of the 2030s.[19]
Einstein Telescope
[edit]Einstein Telescope is a European project for a third-generation detector; it is currently planned to use a design with three 10 km arms arranged in an equilateral triangle (effectively acting as 3 interferometers), which would be built underground; it would also use cryogenic mirrors. It is currently planned to be completed around 2035, with construction starting in 2026.
![](https://upload.wikimedia.org/wikipedia/commons/thumb/2/2f/The_Gravitational_wave_spectrum_Sources_and_Detectors.jpg/220px-The_Gravitational_wave_spectrum_Sources_and_Detectors.jpg)
Science case
[edit]![](https://upload.wikimedia.org/wikipedia/commons/thumb/c/c4/MergingBlackHoles_V2.jpg/220px-MergingBlackHoles_V2.jpg)
Ground-based detectors are designed to study gravitational waves from astrophysical sources. By design, they can only detect waves with a frequency ranging from a few Hz to a few thousand of Hz. The main known gravitational-wave emitting systems within this range are: black hole and/or neutron star binary mergers, rotating neutron stars, bursts and supernovae explosions, and even the gravitational wave background generated in the instants following the Big Bang. Moreover, gravitational radiation may also lead to the discovery of unexpected and theoretically predicted exotic objects.
Transient sources
[edit]![](https://upload.wikimedia.org/wikipedia/commons/thumb/f/fe/GW170817_Gravitational_Wave_Chirp_Spectrogram.jpg/220px-GW170817_Gravitational_Wave_Chirp_Spectrogram.jpg)
Coalescences of black holes and neutron stars
[edit]When two massive and compact objects such as black holes and neutron stars orbit each other in a binary system, they emit gravitational radiation and, therefore, lose energy. Hence, they begin to get closer to each other, increasing the frequency and the amplitude of the gravitational waves; this first phase of the coalescence phenomenon, called the "inspiral", can last for millions of years. This culminates in the merger of the two objects, eventually forming a single compact object (generally a black hole). The part of the waveform corresponding to the merger has the largest amplitude and highest frequency, and can only be modeled by performing numerical relativity simulations of these systems. In the case of black holes, a signal is still emitted during a few seconds after the merger, while the new black hole "settles in"; this signal is known as the "ringdown". Current detectors are only sensitive to the late stages of the coalescence of black hole and neutron star binaries: only the last seconds of the whole process can currently be observed (including the end of the inspiral phase, the merger itself and part of the ringdown). The typical shape of the detectable signal is known as the "chirp", as it resembles the sound emitted by some birds, with a rapid increase in amplitude and frequency. All the gravitational waves signal detected so far originate from black hole or neutron star mergers.[20][21]
Bursts
[edit]![](https://upload.wikimedia.org/wikipedia/commons/thumb/1/19/Eso1733t_Virgo_helps_localise_gravitational-wave_signals.jpg/217px-Eso1733t_Virgo_helps_localise_gravitational-wave_signals.jpg)
Any signal lasting from a few milliseconds to a few seconds is considered a gravitational wave burst.
Supernova explosions—the gravitational collapse of massive stars at the end of their lives—emit gravitational radiation that may be seen by current interferometers.[22] A multi-messenger detection (electromagnetic and gravitational radiation, and neutrinos) would help to better understand the supernova process and the formation of black holes.[23]
Other possible burst candidates include perturbations in neutron stars,[24] "memory" effects arising from the non-linearity of general relativity[25] or cosmic strings.[26] Some phenomena may also generate "long" bursts (longer than 1 second), like instabilities in a black hole accretion disk, or in newly formed black holes and neutron stars when some of the matter ejected during the supernova falls back towards the compact object.[27]
Continuous sources
[edit]The main expected sources of continuous gravitational waves are neutron stars, very compact objects resulting from the collapse of massive stars. In particular, pulsars are special cases of neutron stars that emit light pulses periodically: they can spin up to hundreds of times per second (the fastest spinning pulsar currently known is PSR J1748−2446ad, which spins 716 times per second[28]). Any small deviation from axial symmetry (a tiny "mountain" on the surface) will generate long duration periodic gravitational waves.[29] A number of potential mechanisms have been identified which could generate some "mountains" due to thermal, mechanic, or magnetic effects; accretion may also induce a break in axial symmetry.[30][31][32]
Another possible source of continuous waves in the current detection range could be more exotic objects, such as dark matter candidates. Axions rotating around a black hole[30] or binary systems consisting of a primordial low-mass black hole and another compact object have in particular been suggested as potential sources. Some possible types of dark matter may also be detected by the interferometers directly, by interacting with optical elements of the device.[33]
Stochastic background
[edit]Several physical phenomena may be the source of a gravitational wave stochastic background, an additional source of noise of astrophysical and/or cosmological origin. It represents a (usually) continuous source of gravitational waves, but unlike other continuous wave sources (like rotating neutron stars), it comes from large regions of the sky instead of a single location.[34]
The cosmic microwave background (CMB) is the earliest signal of the Universe that can be observed in the electromagnetic spectrum. However, cosmological models predict the emission of gravitational waves generated instants after the Big Bang. Because gravitational waves interact very weakly with matter, detecting such background would give more insight in the cosmological evolution of our Universe.[35] In particular, it could provide evidence for inflation, from gravitational waves emitted either by the process of inflation itself (according to some theories)[36][37] or at the end of inflation;[38] first-order phase transitions may also produce gravitational waves.[34] Primordial black holes, which may form during the early universe, are also a potential source of a stochastic background for that period.[39]
Moreover, current detectors may be able to detect an astrophysical background resulting from the superposition of all faint and distant sources emitting gravitational waves at all times, which would help to study the evolution of astrophysical sources and star formation. The most likely sources to contribute to the astrophysical background are binary neutron stars,[40] binary black holes,[41] or neutron star-black hole binaries. Other possible sources include supernovae and pulsars.[34] It is expected that this type of background will be the first kind to be detected by the current ground interferometers.[42]
Finally, cosmic strings may represent a source of gravitational wave background, whose detection could provide proof that cosmic strings actually exist.[43][26]
Exotic sources
[edit]Non-conventional, alternative models of compact objects have been proposed by physicists. Some examples of these models can be described within general relativity (quark and strange stars,[44] boson and Proca stars,[45] Kerr black holes with scalar and Proca hair[46]), others arise from some approaches to quantum gravity (cosmic strings,[47] fuzzballs,[48] gravastars[49]), or come from alternative theories of gravity (scalarised neutron stars or black holes, wormholes[50]). Theoretically predicted exotic compact objects could now be detected and would help to elucidate the true nature of gravity or discover new forms of matter. Furthermore, completely unexpected phenomena may be observed, unveiling new physics.
Fundamental properties of gravity
[edit]Gravitational wave polarization
[edit]Gravitational waves are expected to have two "tensor" polarizations, nicknamed "plus" and "cross" due to their effects on a ring of particle (displayed in the figure below). A single gravitational wave is usually a superposition of these two polarizations, depending on the orientation of the source.
In addition, some theories of gravity allow for additional polarizations to exist: the two "vector" polarizations (x and y), and the two "scalar" polarizations ("breathing" and "longitudinal"). Detecting these additional polarizations could provide evidence for physics beyond general relativity.[51]
The polarizations can only be distinguished using several detectors; they could only be properly probed after Virgo was introduced, as the two LIGO detectors are almost co-aligned.[52] They can be measured from compact binary coalescences,[53][54] but also from the stochastic background[55] and continuous waves.[56] With the combination of the current detectors, it is possible to determine the presence or absence of the additional polarizations, but not their nature; a total of 5 independent detectors would be required to fully separate all the polarizations (except for the longitudinal and breathing polarizations, which cannot be distinguished from each other by current detector designs[54]).[57]
- Effect of gravitational wave polarizations on a ring of particles
-
Plus polarization
-
Cross polarization
Lensed gravitational waves
[edit]General relativity predicts that a gravitational wave should be subject to gravitational lensing, just as light waves are; that is, the trajectory of a gravitational wave will be curved by the presence of a massive object (typically a galaxy or a galaxy cluster) near its path.[58] This can result in an increase in the amplitude of the wave, or even multiple observations of the event at different times, as we currently observe for the light of supernovae. Such events are predicted to be common enough to be detected by the current detectors in the near future.[59] Microlensing effects are also predicted.[60] Detecting a lensed event would allow for a very precise localization, as well as further tests of the speed of gravity and of the polarization.[58]
Cosmological measurements
[edit]Gravitational waves also provide a new way to measure some cosmological parameters, and in particular the Hubble constant , which represents the rate of the expansion of the universe and whose value is currently disputed due to conflicting measurement from different methods. The main benefit of this method is that the source luminosity distance measured from the gravitational wave signal does not rely on other measurements or assumptions, as is usually the case. There are two main possibilities for measuring with gravitational waves in current detectors:
- Multi-messenger events with both a gravitational wave and an electromagnetic signal can be used, by measuring the source distance with the gravitational wave signal and their recession velocity by identifying the galaxy in which the event took place, and applying Hubble's law.[61]
- A statistical treatment can be applied to the observed population of binary black hole mergers (often called "dark sirens" in this context), constraining both their mass distribution and ; an external galaxy catalog can also be added to the analysis to improve the measurement to identify possible hosts for the sources.[62]
Testing general relativity
[edit]The measurement of gravitational wave signals offers a unique perspective for testing results from general relativity, as they are produced in environments where the gravitational field is very strong (e.g., near black holes). Such tests may uncover physics beyond general relativity, or possible issues in the models.[63]
- Looking for a residual signal in the data after subtracting models of the signal, which may indicate that some of the signal is not correctly modelled by general relativity.
- Checking that the signal from a merger satisfies some basic assumptions, such as verifying that the estimated parameters of the system are consistent across the different phases of the signal ("inspiral-merger-ringdown consistency test").[66]
- Introducing perturbations in the models for simulating gravitational waves to see if they fit the data.
- Investigating possible dispersion (absent in general relativity but not in alternative theories).[67]
- Analyzing the remnant of a merger, by measuring the post-merger phase of the signal ("ringdown") which is supposed to be fully determined by the mass and spin of the remnant. Such measurements can be the predictions for the energy lost to gravitational waves during the merger and the nature of the remnant object; some hypothetical objects may also feature "echoes" of the ringdown signal.
- Looking for non-standard polarizations (as seen above).
Data analysis
[edit]The detection of gravitational waves within the output of the detectors (typically know as the "strain") is a complex process. Currently, most of the data processing is done within the LIGO-Virgo-KAGRA (LVK) collaboration; teams outside of the collaboration also produce results on the data once it is released publicly.[68]
The data from the current detectors is initially only available to LVK members; segments of data around detected events are released at the time of publication of the related paper, and the full data is released after a proprietary period, currently lasting 18 months. During the third observing run (O3), this resulted in two separated data releases (O3a and O3b), corresponding to the first six months and last six months of the run respectively.[69] The data is then available for anyone on the Gravitational Wave Open Science Center (GWOSC) platform.[70][71]
Transient searches
[edit]Event detection pipelines
[edit]The various softwares used for the analysis of gravitational wave signals are usually referred to as "search pipelines", as they often encompass many steps of the data processing. During the O3 run, five different pipelines were used to identify event candidates within the data and collect a list of observations of short-lived ("transient") gravitational waves signals in a catalog publication. Four of them (GstLAL, PyCBC, MBTA, and SPIIR) were dedicated to the detection of compact binary coalescences (CBC, the only type of event detected so far), while the fifth one (cWB) was designed to detect any transient signal. All five pipelines have been used during the run ("online") as part of the low-latency alert system, and after the run ("offline") to reassess the significance of the candidates and spot events which may have been missed (except for SPIIR, which was only run online)[72] The oLIB pipeline, also looking for generic "burst" signals, has also been used to generate alerts, but not for the catalogs.[73][74] In addition, two other pipelines have been used specifically for burst searches after the run, as they are too computationally expensive to be run online : BayesWave, a pipeline using Bayesian techniques which was used to further investigate events by cWB,[75] and STAMPS-AS, which is designed to look specifically for long-duration bursts (more than 1 second).[27][76]
The four CBC pipelines all rely on the concept of matched filtering, a technique used to search for a known signal within noisy data in an optimal way. This technique requires some knowledge of what the signal looks like, and is thus dependent on the model used to simulate it. Although reasonable models exist, the complexity of the equations governing the dynamics of a compact merger makes the generation of accurate waveforms challenging; the development of new waveforms is still an active field of research.[77][78] In addition, the sources cover a wide range of possible parameters (masses and spins of the two objects, location in the sky) which will yield different waveforms, instead of having one specific signal. This prompts the researchers to generate "template banks" containing a large amount of different waveforms corresponding to different parameters; a compromise has to be done between how tight the bank is (maximizing the number of detections) and the limited computational resources available to carry out the search with all the templates. How to generate such template banks efficiently is also an active field of research.[79] During the search, the matched filtering is performed on every waveform within the (pre-calculated) template bank.
Although the four searches use the same technique, they all have different optimizations and specificities on how they handle the data. In particular, they use different techniques for estimating the significance of an event, for discriminating between real events and glitches, and for combining the data from the different detectors; they also use different template banks.
The cWB (coherent wave burst) pipeline uses a different approach: it works by grouping the data from the different detectors and carrying a joint analysis to look for coherent signals appearing in several detectors at once. Although its sensitivity for binary mergers is less than the dedicated CBC pipelines, its strength lies in being able to detect signals from any kind of sources, as it does not require any assumption on the shape of the signal (which is why it often referred to as an "unmodeled" search).[80]
Low-latency
[edit]The low-latency system is designed to produce alerts for astronomers when gravitational events are detected, with the hope that an electromagnetic counterpart can be observed. This is achieved by centralizing the event candidates from the different analysis pipelines in the gravitational-wave candidate event database (GraceDB),[81] from which the data is processed. If an event is deemed significant enough, a rapid sky localization is produced and preliminary alerts are sent autonomously within the span of a few minutes; after a more precise evaluation of the source parameters, as well as human vetting, a new alert or a retraction notice is sent within a day.[82] The alerts are sent through the GCN, which also centralizes alerts from gamma-ray and neutrino telescopes, as well as SciMMA.[83][84] A total of 78 alerts were sent during the O3 run, of which 23 were later retracted.[72]
Parameter estimation
[edit]After an event has been detected by one of the event detection pipelines, a deeper analysis is performed to get a more precise estimation of the parameters of the source and the measurement uncertainty. During the O3 run, this was carried out using several different pipelines, including Bilby and RIFT. These pipelines employ Bayesian methods to quantify the uncertainty, including MCMC and nested sampling.[72]
Search for counterparts
[edit]While many astronomers try to follow-up the low-latency alerts from gravitational wave detectors, the reverse also exists: electromagnetic events expected to have an associated gravitational wave emission are subjected to a deeper search. One of the prime targets for these are gamma-ray bursts; these are thought to be associated with supernovae ("long" bursts, lasting more than 2 seconds) and with compact binary coalescences involving neutron stars ("short" bursts).[85] The merger of two neutron stars in particular has been confirmed to be associated with both a gamma-ray burst and gravitational waves with the GW170817 event.[40]
Searches targeted toward gamma-ray bursts observations have been performed on data from the past runs using the pyGRB pipeline[86] for CBC, using methods similar to the regular searches, but centered around the time of the bursts and targeting only the sky area found by gamma-ray observatories. An unmodelled search was also carried out using the X-pipeline package, in a similar fashion as regular unmodelled searches.[87][85]
In addition to these searches, several pipelines are looking for coincidences between alerts from gravitational waves and alerts from other detectors. In particular, the RAVEN pipeline is part of the low-latency infrastructure and analyzes the coincidence with gamma-ray burst events and other sources.[88] The LLAMA pipeline is also dedicated to identifying such coincidences with neutrino events, predominantly from IceCube.[89]
Continuous wave searches
[edit]Searches dedicated to periodic gravitational waves—such as the ones generated by rapidly rotating neutron stars—are generally referred to as continuous wave searches. These can be divided in three categories: all-sky searches, which look for unknown signals from any direction, directed searches, which aim for objects with known positions but unknown frequency, and targeted searches, which hunt for signals from sources where both the position and the frequency are known. The directed and targeted searches are motivated by the fact that all-sky searches are extremely computationally expensive, and thus require trade-offs that limit their sensitivity.[30][32]
The principal challenge in continuous wave search is that the signal is much weaker than current detected transients, meaning that one must observe a long time period to accumulate enough data to detect it, as the signal-to-noise ratio scales with the square root of the observing time (intuitively, the signal will add up over the observing duration while the noise will not).[90] The issue is that over such long periods of time, the frequency from the source will evolve, and the motion of the Earth around the Sun will affect the frequency via the Doppler effect. This greatly increases the computational cost of the search, even more so when the frequency is unknown. Although there are mitigation strategies, such as semi-coherent searches, where the analysis is performed separately on segments from the data rather than the full data, these result in a loss of sensitivity.[30] Other approaches include cross-correlation, inspired by stochastic wave searches, which takes advantage of having multiple detectors to look for a correlated signal in a pair of detectors.[91]
Stochastic wave searches
[edit]The stochastic gravitational wave background is another target for data analysis teams. By definition, it can be seen as a source of noise in the detectors; the main challenge is to separate it from the other sources of noise, and measure its power spectral density. The easiest method for solving this issue is to look for correlations within a network of several detectors; the idea being that the noise related to the gravitational wave background will be identical in all detectors, while the instrumental noise will (in principle) not be correlated across the detectors. Another possible approach would be to look for excess power not accounted by other noise sources; however, this proves impractical for current interferometers as the noise is not known well enough compared to the expected power of the stochastic background.[92] Only searches based on cross-correlation between detectors are currently in use by the LVK collaboration,[93] although other types of searches are also developed.[94][95]
This kind of search must also account for factors such as the detectors antenna pattern, the motion of the Earth, and the distance between the detectors. Assumptions also have to be made on some properties of the background; it is common to assume that it is Gaussian and isotropic, but searches for anisotropic, non-Gaussian, and more exotic backgrounds also exist.[92][94]
Gravitational wave properties searches
[edit]A number of software have been developed to investigate the physics surrounding gravitational waves. These analyses are generally performed offline (after the run), and often rely on the results from the other searches (currently mostly CBC searches).
Several analyses are performed to look for events observed multiple time due to lensing, first by trying to match all the known events together, and then by performing a joint analysis for the most promising pair of events; these analyses have been performed using LALInference and HANABI software. Additional searches for events which may have been missed by the regular CBC searches are also performed, by reusing the existing CBC pipelines.[58]
Software designed for estimating the Hubble constant has also been developed. The gwcosmo pipeline performs a Bayesian analysis to determine a distribution of the possible values of the constant, both using "dark sirens" (CBC events without electromagnetic counterpart), which can be correlated with a galaxy catalog, and events with an electromagnetic counterpart for which a direct estimation can be made based on the distance measured with gravitational waves and the identified host galaxy.[96][97] This requires assuming a specific population of black holes, which may be a significant source of bias; recent analyses have been trying to circumvent this issue by fitting both the population and the Hubble constant simultaneously.[98]
References
[edit]- ^ Einstein, Albert (1916-01-01). "Näherungsweise Integration der Feldgleichungen der Gravitation" [Approximative Integration of the Field Equations of Gravitation]. Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften (Minutes of the Royal Prussian Academy of Sciences) (in German): 688–696. Bibcode:1916SPAW.......688E.
- ^ Bersanetti, Diego; Patricelli, Barbara; Piccinni, Ornella Juliana; Piergiovanni, Francesco; Salemi, Francesco; Sequino, Valeria (August 2021). "Advanced Virgo: Status of the Detector, Latest Results and Future Prospects". Universe. 7 (9): 322. Bibcode:2021Univ....7..322B. doi:10.3390/universe7090322. hdl:11568/1161730. ISSN 2218-1997.
- ^ Adele La Rana; Leopoldo Milano (2017), "The early history of gravitational wave detection in Italy: from the first resonant bars to the beginning of the Virgo collaboration", Società Italiana degli Storici della Fisica e dell'Astronomia: Atti del XXXVI Convegno annuale, Napoli 2016 / Proceedings of the 36th Annual Conference, Pavia University Press, doi:10.23739/9788869520709/c17, ISBN 978-88-6952-070-9, retrieved 2024-05-05
- ^ "Timeline". LIGO Lab | Caltech. Retrieved 2024-05-07.
- ^ "Virgo History". Virgo. Retrieved 2024-05-07.
- ^ "IGWN | Observing Plans". observing.docs.ligo.org. Retrieved 2024-05-07.
- ^ "GraceDB | LVK Public Alerts". gracedb.ligo.org. Retrieved 2024-05-07.
- ^ Vinet, Jean-Yves; The Virgo Collaboration (2006). The VIRGO physics book Vol. II (PDF). p. 19.
- ^ T. Accadia; et al. (2012). "Virgo: a laser interferometer to detect gravitational waves". Journal of Instrumentation. 7 (3): P03012. Bibcode:2012JInst...7.3012A. doi:10.1088/1748-0221/7/03/P03012.
- ^ a b G. Vajente (2008). Analysis of sensitivity and noise sources for the Virgo gravitational wave interferometer (PDF).
- ^ Accadia, T.; Acernese, F.; Antonucci, F.; et al. (2011). "Performance of the Virgo interferometer longitudinal control system during the second science run". Astroparticle Physics. 34 (7): 521–527. Bibcode:2011APh....34..521A. doi:10.1016/j.astropartphys.2010.11.006. ISSN 0927-6505.
- ^ Hello, Patrice (December 1996). Couplings in interferometric gravitational wave detectors.
{{cite book}}
: CS1 maint: date and year (link) - ^ Robinet, F.; et al. (2010). "Data quality in gravitational wave bursts and inspiral searches in the second Virgo Science Run". Classical and Quantum Gravity. 27 (19): 194012. Bibcode:2010CQGra..27s4012R. doi:10.1088/0264-9381/27/19/194012. S2CID 120922616.
- ^ Akutsu, T.; Ando, M.; Arai, K.; Arai, Y.; Araki, S.; Araya, A.; Aritomi, N.; Asada, H.; Aso, Y.; Atsuta, S.; Awai, K.; Bae, S.; Baiotti, L.; Barton, M. A.; Cannon, K. (2019-01-08). "KAGRA: 2.5 Generation Interferometric Gravitational Wave Detector". Nature Astronomy. 3 (1): 35–40. arXiv:1811.08079. doi:10.1038/s41550-018-0658-y. ISSN 2397-3366.
- ^ "A brief history of GEO600". www.geo600.org. Retrieved 2024-04-05.
- ^ NAOJ, National Astronomical Observatory of Japan (28 April 2020). "TAMA300 Blazes Trail for Improved Gravitational Wave Astronomy".
- ^ Yamamoto, K; Uchiyama, T; Miyoki, S; Ohashi, M; Kuroda, K; Ishitsuka, H; Akutsu, T; Telada, S; Tomaru, T; Suzuki, T; Sato, N; Saito, Y; Higashi, Y; Haruyama, T; Yamamoto, A (2008-07-01). "Current status of the CLIO project". Journal of Physics: Conference Series. 122: 012002. arXiv:0805.2384. doi:10.1088/1742-6596/122/1/012002. ISSN 1742-6596.
- ^ Krishna, Chetna (2024-02-13). "LIGO comes to India | symmetry magazine". www.symmetrymagazine.org. Retrieved 2024-04-05.
- ^ "Cosmic Explorer". cosmicexplorer.org. Retrieved 2024-04-05.
- ^ "Astrophysical Sources of Gravitational Waves – Virgo". www.virgo-gw.eu. Retrieved 2023-03-31.
- ^ "LIGO Scientific Collaboration – The science of LSC research". www.ligo.org. Retrieved 2023-03-31.
- ^ Kotake, Kei (2013-04-01). "Multiple physical elements to determine the gravitational-wave signatures of core-collapse supernovae". Comptes rendus de l'Académie des Sciences. 14 (4): 318–351. arXiv:1110.5107. Bibcode:2013CRPhy..14..318K. doi:10.1016/j.crhy.2013.01.008. ISSN 1631-0705. S2CID 119112669.
- ^ Kotake, Kei; Takiwaki, Tomoya; Suwa, Yudai; Iwakami Nakano, Wakana; Kawagoe, Shio; Masada, Youhei; Fujimoto, Shin-ichiro (2012-11-07). "Multimessengers from Core-Collapse Supernovae: Multidimensionality as a Key to Bridge Theory and Observation". Advances in Astronomy. 2012: e428757. arXiv:1204.2330. Bibcode:2012AdAst2012E..39K. doi:10.1155/2012/428757. ISSN 1687-7969.
- ^ The LIGO Scientific Collaboration; Abadie, J.; Abbott, B. P.; Abbott, R.; Adhikari, R.; Ajith, P.; Allen, B.; Allen, G.; Amador Ceron, E.; Amin, R. S.; Anderson, S. B.; Anderson, W. G.; Arain, M. A.; Araya, M.; Aso, Y. (2011-02-01). "Search for gravitational waves associated with the August 2006 timing glitch of the Vela pulsar". Physical Review D. 83 (4): 042001. arXiv:1011.1357. Bibcode:2011PhRvD..83d2001A. doi:10.1103/PhysRevD.83.042001.
- ^ Ebersold, Michael; Tiwari, Shubhanshu (2020-05-21). "Search for nonlinear memory from subsolar mass compact binary mergers". Physical Review D. 101 (10): 104041. arXiv:2005.03306. Bibcode:2020PhRvD.101j4041E. doi:10.1103/PhysRevD.101.104041. S2CID 218538344.
- ^ a b Abbott, R.; Abbott, T. D.; Abraham, S.; Acernese, F.; Ackley, K.; Adams, A.; Adams, C.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D. (2021-06-16). "Constraints on Cosmic Strings Using Data from the Third Advanced LIGO–Virgo Observing Run". Physical Review Letters. 126 (24): 241102. arXiv:2101.12248. Bibcode:2021PhRvL.126x1102A. doi:10.1103/PhysRevLett.126.241102. hdl:1721.1/139689.2. ISSN 0031-9007. PMID 34213926. S2CID 231728406.
- ^ a b Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adhikari, N.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L. (2021-11-11). "All-sky search for long-duration gravitational-wave bursts in the third Advanced LIGO and Advanced Virgo run". Physical Review D. 104 (10): 102001. arXiv:2107.13796. Bibcode:2021PhRvD.104j2001A. doi:10.1103/PhysRevD.104.102001. ISSN 2470-0010. S2CID 236493220.
- ^ Hessels, Jason W. T.; Ransom, Scott M.; Stairs, Ingrid H.; Freire, Paulo C. C.; Kaspi, Victoria M.; Camilo, Fernando (2006-03-31). "A Radio Pulsar Spinning at 716 Hz". Science. 311 (5769): 1901–1904. arXiv:astro-ph/0601337. Bibcode:2006Sci...311.1901H. doi:10.1126/science.1123430. ISSN 0036-8075. PMID 16410486. S2CID 14945340.
- ^ Aasi, J.; Abadie, J.; Abbott, B. P.; Abbott, R.; Abbott, T.; Abernathy, M. R.; Accadia, T.; Acernese, F.; Adams, C.; Adams, T.; Adhikari, R. X.; Affeldt, C.; Agathos, M.; Aggarwal, N.; Aguiar, O. D. (2014-04-20). "Gravitational Waves from Known Pulsars: Results from the Initial Detector Era". The Astrophysical Journal. 785 (2): 119. arXiv:1309.4027. Bibcode:2014ApJ...785..119A. doi:10.1088/0004-637X/785/2/119. hdl:1721.1/92734. ISSN 0004-637X. S2CID 215729501.
- ^ a b c d Riles, Keith (2023). "Searches for continuous-wave gravitational radiation". Living Reviews in Relativity. 26 (1): 3. arXiv:2206.06447. Bibcode:2023LRR....26....3R. doi:10.1007/s41114-023-00044-3. S2CID 249642127.
- ^ Sieniawska, Magdalena; Bejger, Michał (November 2019). "Continuous Gravitational Waves from Neutron Stars: Current Status and Prospects". Universe. 5 (11): 217. arXiv:1909.12600. Bibcode:2019Univ....5..217S. doi:10.3390/universe5110217. ISSN 2218-1997.
- ^ a b Piccinni, Ornella Juliana (June 2022). "Status and Perspectives of Continuous Gravitational Wave Searches". Galaxies. 10 (3): 72. arXiv:2202.01088. Bibcode:2022Galax..10...72P. doi:10.3390/galaxies10030072. ISSN 2075-4434.
- ^ LIGO Scientific Collaboration, Virgo Collaboration, and KAGRA Collaboration; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adhikari, N.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D. (2022-03-31). "Constraints on dark photon dark matter using data from LIGO's and Virgo's third observing run". Physical Review D. 105 (6): 063030. arXiv:2105.13085. Bibcode:2022PhRvD.105f3030A. doi:10.1103/PhysRevD.105.063030. S2CID 235212543.
{{cite journal}}
: CS1 maint: multiple names: authors list (link) - ^ a b c Christensen, Nelson (2019-01-01). "Stochastic gravitational wave backgrounds". Reports on Progress in Physics. 82 (1): 016903. arXiv:1811.08797. Bibcode:2019RPPh...82a6903C. doi:10.1088/1361-6633/aae6b5. ISSN 0034-4885. PMID 30462612. S2CID 53712558.
- ^ Bar-Kana, Rennan (1994-07-15). "Limits on direct detection of gravitational waves". Physical Review D. 50 (2): 1157–1160. arXiv:astro-ph/9401050. Bibcode:1994PhRvD..50.1157B. doi:10.1103/PhysRevD.50.1157. PMID 10017813. S2CID 17756178.
- ^ Lopez, Alejandro; Freese, Katherine (2015-01-28). "First test of high frequency Gravity Waves from inflation using Advanced LIGO". Journal of Cosmology and Astroparticle Physics. 2015 (1): 037. arXiv:1305.5855. Bibcode:2015JCAP...01..037L. doi:10.1088/1475-7516/2015/01/037. ISSN 1475-7516. S2CID 118722983.
- ^ Barnaby, Neil; Pajer, Enrico; Peloso, Marco (2012-01-23). "Gauge field production in axion inflation: Consequences for monodromy, non-Gaussianity in the CMB, and gravitational waves at interferometers". Physical Review D. 85 (2): 023525. arXiv:1110.3327. Bibcode:2012PhRvD..85b3525B. doi:10.1103/PhysRevD.85.023525. S2CID 119269863.
- ^ Easther, Richard; Giblin, John T.; Lim, Eugene A. (2007-11-26). "Gravitational Wave Production at the End of Inflation". Physical Review Letters. 99 (22): 221301. arXiv:astro-ph/0612294. Bibcode:2007PhRvL..99v1301E. doi:10.1103/PhysRevLett.99.221301. PMID 18233276. S2CID 43736564.
- ^ Renzini, Arianna I.; Goncharov, Boris; Jenkins, Alexander C.; Meyers, Patrick M. (February 2022). "Stochastic Gravitational-Wave Backgrounds: Current Detection Efforts and Future Prospects". Galaxies. 10 (1): 34. arXiv:2202.00178. Bibcode:2022Galax..10...34R. doi:10.3390/galaxies10010034. ISSN 2075-4434.
- ^ a b Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Afrough, M.; Agarwal, B.; Agathos, M. (2018-02-28). "GW170817: Implications for the Stochastic Gravitational-Wave Background from Compact Binary Coalescences". Physical Review Letters. 120 (9): 091101. arXiv:1710.05837. Bibcode:2018PhRvL.120i1101A. doi:10.1103/PhysRevLett.120.091101. PMID 29547330. S2CID 3889124.
- ^ LIGO Scientific Collaboration and Virgo Collaboration; Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abernathy, M. R.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K. (2016-03-31). "GW150914: Implications for the Stochastic Gravitational-Wave Background from Binary Black Holes". Physical Review Letters. 116 (13): 131102. arXiv:1602.03847. Bibcode:2016PhRvL.116m1102A. doi:10.1103/PhysRevLett.116.131102. PMID 27081965. S2CID 216147156.
- ^ Abbott, R.; Abbott, T. D.; Abraham, S.; Acernese, F.; Ackley, K.; Adams, A.; Adams, C.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D. (2021-07-23). "Upper limits on the isotropic gravitational-wave background from Advanced LIGO and Advanced Virgo's third observing run". Physical Review D. 104 (2): 022004. arXiv:2101.12130. Bibcode:2021PhRvD.104b2004A. doi:10.1103/PhysRevD.104.022004. ISSN 2470-0010. S2CID 231719405.
- ^ Chang, Chia-Feng; Cui, Yanou (2022-03-17). "Gravitational waves from global cosmic strings and cosmic archaeology". Journal of High Energy Physics. 2022 (3): 114. arXiv:2106.09746. Bibcode:2022JHEP...03..114C. doi:10.1007/JHEP03(2022)114. ISSN 1029-8479. S2CID 235485257.
- ^ Wang, Xu; Huang, Yong-Feng; Li, Bing (2021-09-30). "Searching For Strange Quark Planets". arXiv:2109.15161 [astro-ph.HE].
- ^ Pacilio, Costantino; Vaglio, Massimo; Maselli, Andrea; Pani, Paolo (2020-10-05). "Gravitational-wave detectors as particle-physics laboratories: Constraining scalar interactions with a coherent inspiral model of boson-star binaries". Physical Review D. 102 (8): 083002. arXiv:2007.05264. Bibcode:2020PhRvD.102h3002P. doi:10.1103/PhysRevD.102.083002. ISSN 2470-0010. S2CID 222129943.
- ^ Heisenberg, Lavinia; Kase, Ryotaro; Minamitsuji, Masato; Tsujikawa, Shinji (2017-10-24). "Hairy black-hole solutions in generalized Proca theories". Physical Review D. 96 (8): 084049. arXiv:1705.09662. doi:10.1103/PhysRevD.96.084049.
- ^ Auclair, Pierre; Blasi, Simone; Brdar, Vedran; Schmitz, Kai (2023). "Gravitational waves from current-carrying cosmic strings". Journal of Cosmology and Astroparticle Physics. 2023 (4): 009. arXiv:2207.03510. Bibcode:2023JCAP...04..009A. doi:10.1088/1475-7516/2023/04/009. S2CID 250408251.
- ^ Mayerson, Daniel R. (2020-11-25). "Fuzzballs and observations". General Relativity and Gravitation. 52 (12): 115. arXiv:2010.09736. Bibcode:2020GReGr..52..115M. doi:10.1007/s10714-020-02769-w. ISSN 0001-7701. S2CID 224803627.
- ^ Wang, Yu-Tong; Zhang, Jun; Piao, Yun-Song (2019-08-10). "Primordial gravastar from inflation". Physics Letters B. 795: 314–318. arXiv:1810.04885. Bibcode:2019PhLB..795..314W. doi:10.1016/j.physletb.2019.06.036. ISSN 0370-2693. S2CID 118970977.
- ^ Zhang, Hong; Hou, Shaoqi; Bao, Shou-shan (2023-02-08). "Searching for wormholes with gravitational wave scattering". The European Physical Journal C. 83 (2): 127. doi:10.1140/epjc/s10052-023-11281-9. ISSN 1434-6052.
- ^ Eardley, Douglas M.; Lee, David L.; Lightman, Alan P.; Wagoner, Robert V.; Will, Clifford M. (1973-04-30). "Gravitational-Wave Observations as a Tool for Testing Relativistic Gravity". Physical Review Letters. 30 (18): 884–886. Bibcode:1973PhRvL..30..884E. doi:10.1103/PhysRevLett.30.884. hdl:2060/19730012613. S2CID 120335306.
- ^ Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Afrough, M.; Agarwal, B.; Agathos, M.; Agatsuma, K. (2017-10-06). "GW170814: A Three-Detector Observation of Gravitational Waves from a Binary Black Hole Coalescence". Physical Review Letters. 119 (14): 141101. arXiv:1709.09660. Bibcode:2017PhRvL.119n1101A. doi:10.1103/PhysRevLett.119.141101. ISSN 0031-9007. PMID 29053306. S2CID 46829350.
- ^ Takeda, Hiroki; Nishizawa, Atsushi; Michimura, Yuta; Nagano, Koji; Komori, Kentaro; Ando, Masaki; Hayama, Kazuhiro (2018-07-12). "Polarization test of gravitational waves from compact binary coalescences". Physical Review D. 98 (2): 022008. arXiv:1806.02182. Bibcode:2018PhRvD..98b2008T. doi:10.1103/PhysRevD.98.022008. S2CID 119234628.
- ^ a b Isi, Maximiliano; Weinstein, Alan J. (2017-10-10). "Probing gravitational wave polarizations with signals from compact binary coalescences". arXiv:1710.03794 [gr-qc].
- ^ Callister, Thomas; Biscoveanu, A. Sylvia; Christensen, Nelson; Isi, Maximiliano; Matas, Andrew; Minazzoli, Olivier; Regimbau, Tania; Sakellariadou, Mairi; Tasson, Jay; Thrane, Eric (2017-12-07). "Polarization-Based Tests of Gravity with the Stochastic Gravitational-Wave Background". Physical Review X. 7 (4): 041058. arXiv:1704.08373. Bibcode:2017PhRvX...7d1058C. doi:10.1103/PhysRevX.7.041058. S2CID 118992565.
- ^ Isi, Maximiliano; Pitkin, Matthew; Weinstein, Alan J. (2017-08-15). "Probing dynamical gravity with the polarization of continuous gravitational waves". Physical Review D. 96 (4): 042001. arXiv:1703.07530. Bibcode:2017PhRvD..96d2001I. doi:10.1103/PhysRevD.96.042001. S2CID 3674818.
- ^ Chatziioannou, Katerina; Yunes, Nicolás; Cornish, Neil (2012-07-23). "Model-independent test of general relativity: An extended post-Einsteinian framework with complete polarization content". Physical Review D. 86 (2): 022004. arXiv:1204.2585. Bibcode:2012PhRvD..86b2004C. doi:10.1103/PhysRevD.86.022004. S2CID 118890287.
- ^ a b c Abbott, R.; et al. (2021). "Search for Lensing Signatures in the Gravitational-Wave Observations from the First Half of LIGO–Virgo's Third Observing Run". The Astrophysical Journal. 923 (1): 14. arXiv:2105.06384. Bibcode:2021ApJ...923...14A. doi:10.3847/1538-4357/ac23db. S2CID 234482851.
- ^ Li, Shun-Sheng; Mao, Shude; Zhao, Yuetong; Lu, Youjun (2018-05-11). "Gravitational lensing of gravitational waves: A statistical perspective". Monthly Notices of the Royal Astronomical Society. 476 (2): 2220–2229. arXiv:1802.05089. doi:10.1093/mnras/sty411. ISSN 0035-8711.
- ^ Mishra, Anuj; Meena, Ashish Kumar; More, Anupreeta; Bose, Sukanta; Bagla, J. S. (2021-10-26). "Gravitational Lensing of Gravitational Waves: Effect of Microlens Population in Lensing Galaxies". Monthly Notices of the Royal Astronomical Society. 508 (4): 4869–4886. arXiv:2102.03946. doi:10.1093/mnras/stab2875. ISSN 0035-8711.
- ^ Abbott, B. P.; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adams, T.; Addesso, P.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Afrough, M.; Agarwal, B.; Agathos, M.; Agatsuma, K. (November 2017). "A gravitational-wave standard siren measurement of the Hubble constant". Nature. 551 (7678): 85–88. arXiv:1710.05835. Bibcode:2017Natur.551...85A. doi:10.1038/nature24471. ISSN 1476-4687. PMID 29094696. S2CID 205261622.
- ^ The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration; Abbott, R.; Abe, H.; Acernese, F.; Ackley, K.; Adhikari, N.; Adhikari, R. X.; Adkins, V. K.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K. (2023). "Constraints on the Cosmic Expansion History from GWTC–3". The Astrophysical Journal. 949 (2): 76. arXiv:2111.03604. Bibcode:2023ApJ...949...76A. doi:10.3847/1538-4357/ac74bb. S2CID 243832919.
- ^ Krishnendu, N. V.; Ohme, Frank (December 2021). "Testing General Relativity with Gravitational Waves: An Overview". Universe. 7 (12): 497. arXiv:2201.05418. Bibcode:2021Univ....7..497K. doi:10.3390/universe7120497. ISSN 2218-1997.
- ^ Van Den Broeck, Chris (2014), Ashtekar, Abhay; Petkov, Vesselin (eds.), "Probing Dynamical Spacetimes with Gravitational Waves", Springer Handbook of Spacetime, Springer Handbooks, Berlin, Heidelberg: Springer, pp. 589–613, arXiv:1301.7291, Bibcode:2014shst.book..589V, doi:10.1007/978-3-642-41992-8_27, ISBN 978-3-642-41992-8, S2CID 119242493, retrieved 2023-04-23
- ^ LIGO Scientific Collaboration and Virgo Collaboration; Abbott, R.; Abbott, T. D.; Abraham, S.; Acernese, F.; Ackley, K.; Adams, A.; Adams, C.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D. (2021-06-15). "Tests of general relativity with binary black holes from the second LIGO-Virgo gravitational-wave transient catalog". Physical Review D. 103 (12): 122002. arXiv:2010.14529. Bibcode:2021PhRvD.103l2002A. doi:10.1103/PhysRevD.103.122002. hdl:1721.1/139692. S2CID 225094618.
- ^ Ghosh, Abhirup; Johnson-McDaniel, Nathan K; Ghosh, Archisman; Mishra, Chandra Kant; Ajith, Parameswaran; Pozzo, Walter Del; Berry, Christopher P L; Nielsen, Alex B; London, Lionel (2018-01-11). "Testing general relativity using gravitational wave signals from the inspiral, merger and ringdown of binary black holes". Classical and Quantum Gravity. 35 (1): 014002. arXiv:1704.06784. Bibcode:2018CQGra..35a4002G. doi:10.1088/1361-6382/aa972e. ISSN 0264-9381. S2CID 119517334.
- ^ Mirshekari, Saeed; Yunes, Nicolás; Will, Clifford M. (2012-01-25). "Constraining Lorentz-violating, modified dispersion relations with gravitational waves". Physical Review D. 85 (2): 024041. arXiv:1110.2720. Bibcode:2012PhRvD..85b4041M. doi:10.1103/PhysRevD.85.024041.
- ^ "Our Collaborations". LIGO Lab | Caltech. Retrieved 2023-02-26.
- ^ "LIGO-M1000066-v27: LIGO Data Management Plan". dcc.ligo.org. Retrieved 2023-02-26.
- ^ "GWOSC". www.gw-openscience.org. Retrieved 2023-03-05.
- ^ The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration; Abbott, R.; Abe, H.; Acernese, F.; Ackley, K.; Adhicary, S.; Adhikari, N.; Adhikari, R. X.; Adkins, V. K.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M. (2023-02-07). "Open Data from the Third Observing Run of LIGO, Virgo, KAGRA, and GEO". The Astrophysical Journal Supplement Series. 267 (2): 29. arXiv:2302.03676. Bibcode:2023ApJS..267...29A. doi:10.3847/1538-4365/acdc9f. S2CID 256627681.
- ^ a b c The LIGO Scientific Collaboration; the Virgo Collaboration; the KAGRA Collaboration; Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adhikari, N.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K. (2023). "GWTC-3: Compact Binary Coalescences Observed by LIGO and Virgo during the Second Part of the Third Observing Run". Physical Review X. 13 (4): 041039. arXiv:2111.03606. Bibcode:2023PhRvX..13d1039A. doi:10.1103/PhysRevX.13.041039.
- ^ Lynch, Ryan; Vitale, Salvatore; Essick, Reed; Katsavounidis, Erik; Robinet, Florent (2017-05-30). "Information-theoretic approach to the gravitational-wave burst detection problem". Physical Review D. 95 (10): 104046. arXiv:1511.05955. Bibcode:2017PhRvD..95j4046L. doi:10.1103/PhysRevD.95.104046. S2CID 53404242.
- ^ Abbott, B. P.; Abbott, R.; Abbott, T. D.; Abraham, S.; Acernese, F.; Ackley, K.; Adams, C.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L. (2019-04-20). "Low-latency Gravitational-wave Alerts for Multimessenger Astronomy during the Second Advanced LIGO and Virgo Observing Run". The Astrophysical Journal. 875 (2): 161. arXiv:1901.03310. Bibcode:2019ApJ...875..161A. doi:10.3847/1538-4357/ab0e8f. ISSN 0004-637X. S2CID 118893781.
- ^ Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adhikari, N.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L. (2021-12-23). "All-sky search for short gravitational-wave bursts in the third Advanced LIGO and Advanced Virgo run". Physical Review D. 104 (12): 122004. arXiv:2107.03701. Bibcode:2021PhRvD.104l2004A. doi:10.1103/PhysRevD.104.122004. hdl:1721.1/142164. ISSN 2470-0010. S2CID 148571627.
- ^ Macquet, A.; Bizouard, M. A.; Christensen, N.; Coughlin, M. (2021-11-19). "Long-duration transient gravitational-wave search pipeline". Physical Review D. 104 (10): 102005. arXiv:2108.10588. Bibcode:2021PhRvD.104j2005M. doi:10.1103/PhysRevD.104.102005. S2CID 237278361.
- ^ Bohé, Alejandro; Shao, Lijing; Taracchini, Andrea; Buonanno, Alessandra; Babak, Stanislav; Harry, Ian W.; Hinder, Ian; Ossokine, Serguei; Pürrer, Michael; Raymond, Vivien; Chu, Tony; Fong, Heather; Kumar, Prayush; Pfeiffer, Harald P.; Boyle, Michael (2017-02-17). "Improved effective-one-body model of spinning, nonprecessing binary black holes for the era of gravitational-wave astrophysics with advanced detectors". Physical Review D. 95 (4): 044028. arXiv:1611.03703. Bibcode:2017PhRvD..95d4028B. doi:10.1103/PhysRevD.95.044028. S2CID 30505492.
- ^ Husa, Sascha; Khan, Sebastian; Hannam, Mark; Pürrer, Michael; Ohme, Frank; Forteza, Xisco Jiménez; Bohé, Alejandro (2016-02-03). "Frequency-domain gravitational waves from nonprecessing black-hole binaries. I. New numerical waveforms and anatomy of the signal". Physical Review D. 93 (4): 044006. arXiv:1508.07250. Bibcode:2016PhRvD..93d4006H. doi:10.1103/PhysRevD.93.044006. S2CID 118429997.
- ^ Coogan, Adam; Edwards, Thomas D. P.; Chia, Horng Sheng; George, Richard N.; Freese, Katherine; Messick, Cody; Setzer, Christian N.; Weniger, Christoph; Zimmerman, Aaron (2022-12-01). "Efficient gravitational wave template bank generation with differentiable waveforms". Physical Review D. 106 (12): 122001. arXiv:2202.09380. Bibcode:2022PhRvD.106l2001C. doi:10.1103/PhysRevD.106.122001. S2CID 254096550.
- ^ Klimenko, S; Yakushin, I; Mercer, A; Mitselmakher, G (2008-06-07). "A coherent method for detection of gravitational wave bursts". Classical and Quantum Gravity. 25 (11): 114029. arXiv:0802.3232. Bibcode:2008CQGra..25k4029K. doi:10.1088/0264-9381/25/11/114029. ISSN 0264-9381. S2CID 209833580.
- ^ "GraceDB | The Gravitational-Wave Candidate Event Database". gracedb.ligo.org. Retrieved 2023-02-28.
- ^ "Data Analysis – IGWN | Public Alerts User Guide". emfollow.docs.ligo.org. Retrieved 2023-02-28.
- ^ "GCN – General Coordinates Network". gcn.nasa.gov. Retrieved 2023-02-28.
- ^ "Scalable Cyberinfrastructure for Multi-messenger Astrophysics". Scalable Cyberinfrastructure for Multi-messenger Astrophysics. Retrieved 2023-02-28.
- ^ a b Abbott, R.; Abbott, T. D.; Acernese, F.; Ackley, K.; Adams, C.; Adhikari, N.; Adhikari, R. X.; Adya, V. B.; Affeldt, C.; Agarwal, D.; Agathos, M.; Agatsuma, K.; Aggarwal, N.; Aguiar, O. D.; Aiello, L. (2022-04-01). "Search for Gravitational Waves Associated with Gamma-Ray Bursts Detected by Fermi and Swift during the LIGO–Virgo Run O3b". The Astrophysical Journal. 928 (2): 186. arXiv:2111.03608. Bibcode:2022ApJ...928..186A. doi:10.3847/1538-4357/ac532b. ISSN 0004-637X. S2CID 243832929.
- ^ Williamson, A. R.; Biwer, C.; Fairhurst, S.; Harry, I. W.; Macdonald, E.; Macleod, D.; Predoi, V. (2014-12-24). "Improved methods for detecting gravitational waves associated with short gamma-ray bursts". Physical Review D. 90 (12): 122004. arXiv:1410.6042. Bibcode:2014PhRvD..90l2004W. doi:10.1103/PhysRevD.90.122004. S2CID 86867428.
- ^ Wąs, Michał; Sutton, Patrick J.; Jones, Gareth; Leonor, Isabel (2012-07-23). "Performance of an externally triggered gravitational-wave burst search". Physical Review D. 86 (2): 022003. arXiv:1201.5599. Bibcode:2012PhRvD..86b2003W. doi:10.1103/PhysRevD.86.022003. S2CID 119158252.
- ^ Cho, Min-A. (2019). Low-Latency Searches for Gravitational Waves and their Electromagnetic Counterparts with Advanced LIGO and Virgo (Thesis). Digital Repository at the University of Maryland. Bibcode:2019PhDT........52C. doi:10.13016/7lp5-glut.
- ^ Countryman, Stefan; Keivani, Azadeh; Bartos, Imre; Marka, Zsuzsa; Kintscher, Thomas; Corley, Rainer; Blaufuss, Erik; Finley, Chad; Marka, Szabolcs (2019-01-16). "Low-Latency Algorithm for Multi-messenger Astrophysics (LLAMA) with Gravitational-Wave and High-Energy Neutrino Candidates". arXiv:1901.05486 [astro-ph.HE].
- ^ "Matched filter and signal-to-noise for a periodic template". Noise to signal. 2016-08-25. Retrieved 2023-03-29.
- ^ Dhurandhar, Sanjeev; Krishnan, Badri; Mukhopadhyay, Himan; Whelan, John T. (2008-04-17). "Cross-correlation search for periodic gravitational waves". Physical Review D. 77 (8): 082001. arXiv:0712.1578. Bibcode:2008PhRvD..77h2001D. doi:10.1103/PhysRevD.77.082001. hdl:11858/00-001M-0000-0013-626B-F. S2CID 41261478.
- ^ a b Romano, Joseph D.; Cornish, Neil. J. (2017). "Detection methods for stochastic gravitational-wave backgrounds: a unified treatment". Living Reviews in Relativity. 20 (1): 2. arXiv:1608.06889. Bibcode:2017LRR....20....2R. doi:10.1007/s41114-017-0004-1. ISSN 2367-3613. PMC 5478100. PMID 28690422.
- ^ Renzini, Arianna I.; Goncharov, Boris; Jenkins, Alexander C.; Meyers, Patrick M. (2022). "Stochastic Gravitational-Wave Backgrounds: Current Detection Efforts and Future Prospects". Galaxies. 10 (1): 34. arXiv:2202.00178. Bibcode:2022Galax..10...34R. doi:10.3390/galaxies10010034. ISSN 2075-4434.
- ^ a b Smith, Rory; Thrane, Eric (2018-04-16). "Optimal Search for an Astrophysical Gravitational-Wave Background". Physical Review X. 8 (2): 021019. arXiv:1712.00688. Bibcode:2018PhRvX...8b1019S. doi:10.1103/PhysRevX.8.021019.
- ^ Lawrence, Jessica; Turbang, Kevin; Matas, Andrew; Renzini, Arianna I.; van Remortel, Nick; Romano, Joseph (2023-05-15). "A stochastic search for intermittent gravitational-wave backgrounds". Physical Review D. 107 (10): 103026. arXiv:2301.07675. Bibcode:2023PhRvD.107j3026L. doi:10.1103/PhysRevD.107.103026. S2CID 255998346.
- ^ Gray, Rachel; Hernandez, Ignacio Magaña; Qi, Hong; Sur, Ankan; Brady, Patrick R.; Chen, Hsin-Yu; Farr, Will M.; Fishbach, Maya; Gair, Jonathan R.; Ghosh, Archisman; Holz, Daniel E.; Mastrogiovanni, Simone; Messenger, Christopher; Steer, Danièle A.; Veitch, John (2020-06-08). "Cosmological inference using gravitational wave standard sirens: A mock data analysis". Physical Review D. 101 (12): 122001. arXiv:1908.06050. Bibcode:2020PhRvD.101l2001G. doi:10.1103/PhysRevD.101.122001. S2CID 201058508.
- ^ Gray, Rachel; Messenger, Chris; Veitch, John (2022-03-21). "A Pixelated Approach to Galaxy Catalogue Incompleteness: Improving the Dark Siren Measurement of the Hubble Constant". Monthly Notices of the Royal Astronomical Society. 512 (1): 1127–1140. arXiv:2111.04629. doi:10.1093/mnras/stac366. ISSN 0035-8711.
- ^ Mastrogiovanni, S.; Leyde, K.; Karathanasis, C.; Chassande-Mottin, E.; Steer, D. A.; Gair, J.; Ghosh, A.; Gray, R.; Mukherjee, S.; Rinaldi, S. (2021-09-20). "On the importance of source population models for gravitational-wave cosmology". Physical Review D. 104 (6): 062009. arXiv:2103.14663. Bibcode:2021PhRvD.104f2009M. doi:10.1103/PhysRevD.104.062009. hdl:1854/LU-8731176. S2CID 232403973.