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NICE—Noise Interactive Catalogue Explorer—is a web service developed for rapid-qualitative glitch analysis in gravitational wave data. Glitches are transient noise events that can smother the gravitational wave signal in data recorded by gravitational wave interferometer detectors. NICE provides interactive graphical tools to support detector noise characterization activities, in particular, the analysis of glitches from past and current observing runs, passing from glitch population visualization to individual glitch characterization. The NICE back-end API consists of a multi-database structure that brings order to glitch metadata generated by external detector characterization tools so that such information can be easily requested by gravitational wave scientists. Another novelty introduced by NICE is the interactive front-end infrastructure focused on glitch instrumental and environmental origin investigation, which uses labels determined by their time–frequency morphology. The NICE domain is intended for integration with the Advanced Virgo, Advanced LIGO, and KAGRA characterization pipelines and it will interface with systematic classification activities related to the transient noise sources present in the Virgo detector.

NICE—Noise Interactive Catalogue Explorer—is a web service developed for rapid-qualitative glitch analysis in gravitational wave data. Glitches are transient noise events that can smother the gravitational wave signal in data recorded by gravitational wave interferometer detectors. NICE provides interactive graphical tools to support detector noise characterization activities, in particular, the analysis of glitches from past and current observing runs, passing from glitch population visualization to individual glitch characterization. The NICE back-end API consists of a multi-database structure that brings order to glitch metadata generated by external detector characterization tools so that such information can be easily requested by gravitational wave scientists. Another novelty introduced by NICE is the interactive front-end infrastructure focused on glitch instrumental and environmental origin investigation, which uses labels determined by their time–frequency morphology. The NICE domain is intended for integration with the Advanced Virgo, Advanced LIGO, and KAGRA characterization pipelines and it will interface with systematic classification activities related to the transient noise sources present in the Virgo detector. [ABSTRACT FROM AUTHOR]

In this paper, we review the theoretical basis for generation of gravitational waves and the detection techniques used to detect a gravitational wave. To materialize this goal in a thorough way, we first start with a mathematical background for general relativity from which a clue for gravitational wave was conceived by Einstein. Thereafter, we give the classification scheme of gravitational waves such as (i) continuous gravitational waves, (ii) compact binary inspiral gravitational waves and (iii) stochastic gravitational wave. Necessary mathematical insight into gravitational waves from binaries is also dealt with which follows detection of gravitational waves based on the frequency classification. Ground-based observatories as well as space borne gravitational wave detectors are discussed in a length. We have provided an overview on the inflationary gravitational waves. In connection to data analysis by matched filtering there are a few highlights on the techniques, e.g. (i) random noise, (ii) power spectrum, (iii) shot noise and (iv) Gaussian noise. Optimal detection statistics for a gravitational wave detection is also in the pipeline of the discussion along with detailed necessity of the matched filter and deep learning. [ABSTRACT FROM AUTHOR]

With the advent of gravitational-wave astronomy and the discovery of more compact binary coalescences, data quality improvement techniques are desired to handle the complex and overwhelming noise in gravitational wave (GW) observational data. Though recent machine learning-based studies have shown promising results for data denoising, they are unable to precisely recover both the GW signal amplitude and phase. To address such an issue, we develop a deep neural network centered workflow, WaveFormer, for significant noise suppression and signal recovery on observational data from the Laser Interferometer Gravitational-Wave Observatory (LIGO). The WaveFormer has a science-driven architecture design with hierarchical feature extraction across a broad frequency spectrum. As a result, the overall noise and glitch are decreased by more than one order of magnitude and the signal recovery error is roughly 1% and 7% for the phase and amplitude, respectively. Moreover, on 75 reported binary black hole events of LIGO we obtain a significant improvement of inverse false alarm rate. Our work highlights the potential of large neural networks in GW data analysis and, while primarily demonstrated on LIGO data, its adaptable design indicates promise for broader application within the International Gravitational-Wave Observatories Network in future observational runs.

Starting with models for the compact object merger event rate, the short-duration gamma-ray burst (sGRB) luminosity function, and the Swift-BAT detector, we calculate the observed Swift sGRB rate and its uncertainty. Our probabilistic sGRB world model reproduces the observed number distributions in redshift and flux for 123 Swift-BAT detected sGRBs and can be used to predict joint sGRB/LIGO detection rates. We discuss the dependence of the rate predictions on the model parameters and explore how they vary with increasing experimental sensitivity. In particular, the number of bursts in the LIGO volume depends strongly on the parameters that govern sGRB beaming. Our results suggest that nearby sGRBs should be observed to have broader jets on average (θ jet ≳ 30°), as compared to the narrowly beamed appearance of cosmological sGRBs due to the detection-selection effect driving the observed jet angle. Assuming all sGRBs are due to compact object mergers, within a D < 200 Mpc aLIGO volume, we predict 0.18 − 0.08 + 0.19 sGRB–gravitational wave (GW) associations all sky per year for on-axis events at Swift sensitivities, increasing to 1.2 − 0.6 + 1.9 with the inclusion of off-axis events. We explore the consistency of our model with GW170817/GRB 170817A in the context of structured jets. Predictions for future experiments are made. [ABSTRACT FROM AUTHOR]

New analyses of gravitational-wave events raise questions about the nature of some events. For example, LIGO–Virgo–KAGRA initially determined GW151226 to be a merger with a mass ratio q ≈ 0.5 and effective inspiral spin χ eff ≈ 0.2. However, recent works offer an alternative picture: GW151226 is a lower mass ratio event q ≈ 0.3 with slightly higher spin χ eff ≈ 0.3. This discrepancy has been challenging to resolve, as a wide range of differences are employed for each analysis. This work introduces a "deep follow-up" framework to efficiently compute the posterior odds between two different peaks in parameter space. In doing so, we aim to help resolve disputes about the true nature of gravitational-wave events associated with conflicting astrophysical interpretations. Our proposal is not a replacement for standard inference techniques; instead, our method provides a diagnostic tool to understand discrepancies between conflicting results. We demonstrate this method by studying three q–χ eff peaks proposed for GW151226. We find that the (q ∼ 0.5, χ eff ∼ 0.2) interpretation is only slightly preferred over the (q ∼ 0.3, χ eff ∼ 0.3) hypothesis with posterior odds of ∼1.7 ± 0.4, suggesting that neither of the two peaks can be ruled out. We discuss strategies to produce more reliable parameter estimation studies in gravitational-wave astronomy. [ABSTRACT FROM AUTHOR]

The gravitational-wave signal GW190521 is consistent with a binary black hole (BBH) merger source at redshift 0.8 with unusually high component masses, 85-14+21 M o˙ and 66-18+17 M o˙, compared to previously reported events, and shows mild evidence for spin-induced orbital precession. The primary falls in the mass gap predicted by (pulsational) pair-instability supernova theory, in the approximate range 65-120 M o˙. The probability that at least one of the black holes in GW190521 is in that range is 99.0%. The final mass of the merger (142-16+28 M o˙) classifies it as an intermediate-mass black hole. Under the assumption of a quasi-circular BBH coalescence, we detail the physical properties of GW190521's source binary and its post-merger remnant, including component masses and spin vectors. Three different waveform models, as well as direct comparison to numerical solutions of general relativity, yield consistent estimates of these properties. Tests of strong-field general relativity targeting the merger-ringdown stages of the coalescence indicate consistency of the observed signal with theoretical predictions. We estimate the merger rate of similar systems to be 0.13-0.11+0.30 Gpc-3 yr-1. We discuss the astrophysical implications of GW190521 for stellar collapse and for the possible formation of black holes in the pair-instability mass gap through various channels: via (multiple) stellar coalescences, or via hierarchical mergers of lower-mass black holes in star clusters or in active galactic nuclei. We find it to be unlikely that GW190521 is a strongly lensed signal of a lower-mass black hole binary merger. We also discuss more exotic possible sources for GW190521, including a highly eccentric black hole binary, or a primordial black hole binary.

The gravitational-wave signal GW190521 is consistent with a binary black hole (BBH) merger source at redshift 0.8 with unusually high component masses, 85-14+21 M o˙ and 66-18+17 M o˙, compared to previously reported events, and shows mild evidence for spin-induced orbital precession. The primary falls in the mass gap predicted by (pulsational) pair-instability supernova theory, in the approximate range 65-120 M o˙. The probability that at least one of the black holes in GW190521 is in that range is 99.0%. The final mass of the merger (142-16+28 M o˙) classifies it as an intermediate-mass black hole. Under the assumption of a quasi-circular BBH coalescence, we detail the physical properties of GW190521's source binary and its post-merger remnant, including component masses and spin vectors. Three different waveform models, as well as direct comparison to numerical solutions of general relativity, yield consistent estimates of these properties. Tests of strong-field general relativity targeting the merger-ringdown stages of the coalescence indicate consistency of the observed signal with theoretical predictions. We estimate the merger rate of similar systems to be 0.13-0.11+0.30 Gpc-3 yr-1. We discuss the astrophysical implications of GW190521 for stellar collapse and for the possible formation of black holes in the pair-instability mass gap through various channels: via (multiple) stellar coalescences, or via hierarchical mergers of lower-mass black holes in star clusters or in active galactic nuclei. We find it to be unlikely that GW190521 is a strongly lensed signal of a lower-mass black hole binary merger. We also discuss more exotic possible sources for GW190521, including a highly eccentric black hole binary, or a primordial black hole binary.

In this paper, we examine the correlation functions associated with intensity interferometry and gravito-optics of gravitational wave (GW) signals from compact binary coalescences (CBC). Previous theoretical studies of the gravito-optics of GWs have concentrated on the characterization of both the classical and the nonclassical properties of signals from cosmological sources in the early Universe. These previous works assume a periodic signal similar to the signals studied widely in optics and quantum optics and do not apply to transient signals. We develop the gravito-optics of intensity correlations for descriptions of the detection of transient signals from CBC and apply these methods to calculate the two-point intensity correlations for the GW discovery. We also discuss the necessary theoretical work required for the description of the quantum gravito-optics of intensity correlations in the detection of signals from binary inspirals. [ABSTRACT FROM AUTHOR]

The response of the Advanced Laser Interferometer Gravitational-wave Observatory (Advanced LIGO) interferometers is known to vary with time (Tuyenbayev et al 2017 Class. Quantum Grav. 34 015002). Accurate calibration of the interferometers must therefore track and compensate for temporal variations in calibration model parameters. These variations were tracked during the first three Advanced LIGO observing runs, and compensation for some of them has been implemented in the calibration procedure. During the second observing run, multiplicative corrections to the interferometer response were applied while producing calibrated strain data both in real time and in high latency. In a high-latency calibration produced after the second observing run and during the entirety of the third observing run, a correction requiring periodic filter updates was applied to the calibration–the time dependence of the coupled cavity pole frequency f c c . This paper describes the methods developed to compensate for variations in the interferometer response requiring time-dependent filters, including variable zeros, poles, gains, and time delays. The described methods were used to provide compensation for well-modeled time dependence of the interferometer response, which has helped to reduce systematic errors in the calibration to < 2% in magnitude and < 2∘ in phase across LIGO's most sensitive frequency band of 20–2000 Hz (Sun et al 2020 Class. Quantum Grav. 37 225008; Sun et al 2021 arXiv:2107.00129 [astro-ph.IM]). Additionally, this paper shows how such compensation is relevant for astrophysical inference studies by reducing uncertainty and bias in the sky localization for a simulated binary neutron star merger. [ABSTRACT FROM AUTHOR]

Upcoming LIGO–Virgo–KAGRA (LVK) observing runs are expected to detect a variety of inspiralling gravitational-wave (GW) events that come from black hole and neutron star binary mergers. Detection of noninspiral GW sources is also anticipated. We report the discovery of a new class of noninspiral GW sources—the end states of massive stars—that can produce the brightest simulated stochastic GW burst signal in the LVK bands known to date, and could be detectable in LVK run A+. Some dying massive stars launch bipolar relativistic jets, which inflate a turbulent energetic bubble—cocoon—inside of the star. We simulate such a system using state-of-the-art 3D general relativistic magnetohydrodynamic simulations and show that these cocoons emit quasi-isotropic GW emission in the LVK band, ∼10–100 Hz, over a characteristic jet activity timescale ∼10–100 s. Our first-principles simulations show that jets exhibit a wobbling behavior, in which case cocoon-powered GWs might be detected already in LVK run A+, but it is more likely that these GWs will be detected by the third-generation GW detectors with an estimated rate of ∼10 events yr ^−1 . The detection rate drops to ∼1% of that value if all jets were to feature a traditional axisymmetric structure instead of a wobble. Accompanied by electromagnetic emission from the energetic core-collapse supernova and the cocoon, we predict that collapsars are powerful multimessenger events.

In 2017, the LIGO and Virgo gravitational-wave (GW) detectors, in conjunction with electromagnetic (EM) astronomers, observed the first GW multimessenger astrophysical event, the binary neutron star (BNS) merger GW170817. This marked the beginning of a new era in multimessenger astrophysics. To discover further GW multimessenger events, we explore the synergies between the Transiting Exoplanet Survey Satellite (TESS) and GW observations triggered by the LIGO–Virgo–KAGRA Collaboration (LVK) detector network. TESS's extremely wide field of view (∼2300 deg ^2 ) means that it could overlap with large swaths of GW localizations, which often span hundreds of square degrees or more. In this work, we use a recently developed transient detection pipeline to search TESS data collected during the LVK’s third observing run, O3, for any EM counterparts. We find no obvious counterparts brighter than about 17th magnitude in the TESS bandpass. Additionally, we present end-to-end simulations of BNS mergers, including their detection in GWs and simulations of light curves, to identify TESS's kilonova discovery potential for the LVK's next observing run (O4). In the most optimistic case, TESS will observe up to one GW-found BNS merger counterpart per year. However, TESS may also find up to five kilonovae that did not trigger the LVK network, emphasizing that EM-triggered GW searches may play a key role in future kilonova detections. We also discuss how TESS can help place limits on EM emission from binary black hole mergers and rapidly exclude large sky areas for poorly localized GW events.

The general principles of gravitational waves detection are considered in this paper. Current gravitational wave detectors represent modernized Michelson interferometer – LIGO-detector. Reduction of vibrations in the system and high stabilization of the reflective mirrors is one of the technical problem of the LIGO. It is proposed to study the features of the LIGO-detector with movable mirrors. The software simulating the operation of the LIGO and providing an opportunity to study its characteristics and capacity is developed and named «LIGO-RM». The primary goal of the modelling is to study the signal of the gravitational waves detector with oscillating mirrors. The «LIGO-RM» contains graphic user interface (GUI) that provides interactive control of mirrors movement nature and monitoring of detector signal change. The software simulates the presence of gravitational wave of a requested type and makes it able to monitor its effect on the operation results of the LIGO interferometer in interactive mode or as a numerical outcome. A range of numerical experiments is conducted and the signals on the detector with and without mirrors oscillations are shown. The results of calculations and a possibility of the registration of the gravitational waves using the LIGO-detector with movable mirrors are discussed.

Scattered light noise (or scattering) affects the sensitivity of gravitational wave detectors in their detection frequency band. The mitigation of such nonlinear and nonstationary noise can be carried out experimentally and employing data analysis techniques, e.g., applying adaptive algorithms to the data affected by noise. We present gwas , a fully automated pipeline based on the time-varying filter empirical mode decomposition (tvf-EMD) algorithm, to identify, characterize, and monitor objects inducing scattering to the gravitational wave detector’s output. The tvf-EMD algorithm is suitable for decomposing signals with time-dependent frequency, such as scattering. The pipeline application to LIGO Livingston data shows that most of the scattering noise present in the third observation run was due to the penultimate mass at the end of the X-arm of the detector (EXPUM), whose motion is excited in the 0.1 Hz to 0.3 Hz frequency range (so-called microseismic band). Furthermore, we show that the pipeline can perform daily analyses, and we test it on six days of LIGO Livingston data. These analyses allowed monitoring of the onset and time evolution of scattering due to the EXPUM in connection with the variability of microseismic band noise measured at the detector site. [ABSTRACT FROM AUTHOR]

We explore a method to assess the relative scale of the strain measured in the different detectors of the gravitational-wave (GW) network, using binary black hole (BBH) events detected during the third observing run (O3). The number of such signals is becoming sufficiently large to adopt a statistical approach based on the ratio of the signal-to-noise ratio of the events between the detectors and the number of observed events in each detector. We demonstrate the principle of the method on simulations of BBH signals and we present its application to published O3 events reported by the multi-band template analysis pipeline. Constraints on the relative calibration of the GW network for O3 are obtained at the level of ∼ 3.5 % between the two LIGO detectors and at the level of ∼ 10 % between the LIGO Livingston detector and the Virgo detector. [ABSTRACT FROM AUTHOR]

The mass of a Kerr black hole (BH) can be separated into irreducible and rotational componentsâ€"the former is a lower limit to the energy that cannot be possibly extracted from the event horizon and is related to its area. Here we compute the irreducible masses of the stellar-mass BHs observed by gravitational-wave interferometers LIGO and Virgo. Using single-event data, we present a re-parameterization of the posterior distribution that explicitly highlights the irreducible and rotational contributions to the total energy. We exploit the area law to rank the black-hole mergers observed to date according to their irreversibility, thus providing a guide to selecting events for targeted tests of general relativity. Using population fits, we compute the rate by which the total area of black-hole horizons increases due to the observable mergers. [ABSTRACT FROM AUTHOR]

The relative velocity between objects with finite velocity affects the reaction between them. This effect is known as general Doppler effect. The Laser Interferometer Gravitational-Wave Observatory (LIGO) discovered gravitational waves and found their speed to be equal to the speed of light c. Gravitational waves are generated following a disturbance in the gravitational field; they affect the gravitational force on an object. Just as light waves are subject to the Doppler effect, so are gravitational waves. This article explores the following research questions concerning gravitational waves: Is there a linear relationship between gravity and velocity? Can the speed of a gravitational wave represent the speed of the gravitational field (the speed of the action of the gravitational field upon the object)? What is the speed of the gravitational field? What is the spatial distribution of gravitational waves? Do gravitational waves caused by the revolution of the Sun affect planetary precession? Can we modify Newton's gravitational equation through the influence of gravitational waves? [ABSTRACT FROM AUTHOR]

The birth of gravitational wave astronomy was triggered by the first detection of a signal produced by the merger of two compact objects (also known as a compact binary coalescence event). The following detections made by the Earth-based network of advanced interferometers had a significant impact in many fields of science: astrophysics, cosmology, nuclear physics and fundamental physics. However, compact binary coalescence signals are not the only type of gravitational waves potentially detectable by LIGO, Virgo, and KAGRA. An interesting family of still undetected signals, and the ones that are considered in this review, are the so-called continuous waves, paradigmatically exemplified by the gravitational radiation emitted by galactic, fast-spinning isolated neutron stars with a certain degree of asymmetry in their mass distribution. In this work, I will review the status and the latest results from the analyses of advanced detector data. [ABSTRACT FROM AUTHOR]

Core-collapse supernovae (CCSNe) are predicted to produce gravitational waves (GWs) that may be detectable by Advanced LIGO/Virgo. These GW signals carry information from the heart of these cataclysmic events, where matter reaches nuclear densities. Recent studies have shown that it may be possible to infer the properties of the proto-neutron star (PNS) via GWs generated by hydrodynamic perturbations of the PNS. However, we lack a comprehensive understanding of how these relationships may change with the properties of CCSNe. In this work, we build a self-consistent suite of over 1000 exploding CCSNe from a grid of progenitor masses and metallicities combined with six different nuclear equations of state (EOS). Performing a linear perturbation analysis on each model, we compute the resonant GW frequencies of the PNS, and we motivate a time-agnostic method for identifying characteristic frequencies of the dominant GW emission. From this, we identify two characteristic frequencies, of the early- and late-time signal, that measure the surface gravity of the cold remnant neutron star, and simultaneously constrain the hot nuclear EOS. However, we find that the details of the CCSN model, such as the treatment of gravity or the neutrino transport, and whether it explodes, noticeably change the magnitude and evolution of the PNS eigenfrequencies.

Starting with models for the compact object merger event rate, the short-duration gamma-ray burst (sGRB) luminosity function, and the Swift-BAT detector, we calculate the observed Swift sGRB rate and its uncertainty. Our probabilistic sGRB world model reproduces the observed number distributions in redshift and flux for 123 Swift-BAT detected sGRBs and can be used to predict joint sGRB/LIGO detection rates. We discuss the dependence of the rate predictions on the model parameters and explore how they vary with increasing experimental sensitivity. In particular, the number of bursts in the LIGO volume depends strongly on the parameters that govern sGRB beaming. Our results suggest that nearby sGRBs should be observed to have broader jets on average ( θ _jet ≳ 30°), as compared to the narrowly beamed appearance of cosmological sGRBs due to the detection-selection effect driving the observed jet angle. Assuming all sGRBs are due to compact object mergers, within a D < 200 Mpc aLIGO volume, we predict ${0.18}_{-0.08}^{+0.19}$ sGRB–gravitational wave (GW) associations all sky per year for on-axis events at Swift sensitivities, increasing to ${1.2}_{-0.6}^{+1.9}$ with the inclusion of off-axis events. We explore the consistency of our model with GW170817/GRB 170817A in the context of structured jets. Predictions for future experiments are made.

New analyses of gravitational-wave events raise questions about the nature of some events. For example, LIGO–Virgo–KAGRA initially determined GW151226 to be a merger with a mass ratio q ≈ 0.5 and effective inspiral spin χ _eff ≈ 0.2. However, recent works offer an alternative picture: GW151226 is a lower mass ratio event q ≈ 0.3 with slightly higher spin χ _eff ≈ 0.3. This discrepancy has been challenging to resolve, as a wide range of differences are employed for each analysis. This work introduces a “deep follow-up” framework to efficiently compute the posterior odds between two different peaks in parameter space. In doing so, we aim to help resolve disputes about the true nature of gravitational-wave events associated with conflicting astrophysical interpretations. Our proposal is not a replacement for standard inference techniques; instead, our method provides a diagnostic tool to understand discrepancies between conflicting results. We demonstrate this method by studying three q–χ _eff peaks proposed for GW151226. We find that the ( q ∼ 0.5, χ _eff ∼ 0.2) interpretation is only slightly preferred over the ( q ∼ 0.3, χ _eff ∼ 0.3) hypothesis with posterior odds of ∼1.7 ± 0.4, suggesting that neither of the two peaks can be ruled out. We discuss strategies to produce more reliable parameter estimation studies in gravitational-wave astronomy.

Direct detection of gravitational waves from several compact binary coalescences has ushered in a new era of astronomy. It has opened up the possibility of detecting ultralight bosons, predicted by extensions of the Standard Model, from their gravitational signatures. This is of particular interest as some of these hypothetical particles could be components of dark matter that are expected to interact very weakly with Standard Model particles, if at all, but they would gravitate as usual. Ultralight bosons can trigger superradiant instabilities of rotating black holes and form bosonic clouds that would emit gravitational waves. In this paper, we present an overview of such instabilities as gravitational wave sources and assess the ability of current and future detectors to shed light on potential dark matter candidates. [ABSTRACT FROM AUTHOR]

Zusammenfassung Seit 2015 wurden in bisher drei Beobachtungsläufen periodische Raumzeitkrümmungen von großen Laserinterferometern gemessen. Das Ergebnis: Fünfzig Gravitationswellensignale konnten in den Daten gefunden werden, die jeweils vom Umkreisen und Verschmelzen von kompakten Doppelsystemen ausgelöst wurden. Zwei dieser beobachteten Systeme bestanden dabei aus Neutronensternen, die anderen Signale entstammen der Verschmelzung von Schwarzen Löchern. Durch diese Messungen wird ein bisher kaum zugänglicher Bereich des Universums nach und nach sichtbar. Es zeichnet sich ab, dass auch in Zukunft die Signale vieler verschmelzender Schwarzer Löcher, die jeweils 10 bis 40 Sonnenmassen schwer sind, den Großteil der Beobachtungen ausmachen werden. Allerdings hat der erst kürzlich analysierte Beobachtungslauf auch einige überraschende Messungen beinhaltet. Doppelsysteme, in denen die Masse nicht symmetrisch auf beide Partner verteilt ist, wurden erstmals beobachtet und ihr „Klang" inklusive Obertöne analysiert. In zumindest einem Fall (GW190814) kann das kleine Objekt im System nicht zweifelsfrei identifiziert werden. Bei GW190521 sind die Schwarzen Löcher dagegen so massereich, dass deren Entstehung Rätsel aufgibt. Weitere Beobachtungsläufe, ebenso wie neuartige Gravitationswelleninstrumente, sind für die Zukunft geplant und werden weitere Einsichten zur Zusammensetzung, Entwicklung und Entstehung des Universums liefern. [ABSTRACT FROM AUTHOR]

The field of gravitational-wave astronomy has been opened up by gravitational-wave observations made with interferometric detectors. This review surveys the current state-of-the-art in gravitational-wave detectors and data analysis methods currently used by the Laser Interferometer Gravitational-Wave Observatory in the United States and the Virgo Observatory in Italy. These analysis methods will also be used in the recently completed KAGRA Observatory in Japan. Data analysis algorithms are developed to target one of four classes of gravitational waves. Short duration, transient sources include compact binary coalescences, and burst sources originating from poorly modeled or unanticipated sources. Long duration sources include sources which emit continuous signals of consistent frequency, and many unresolved sources forming a stochastic background. A description of potential sources and the search for gravitational waves from each of these classes are detailed. [ABSTRACT FROM AUTHOR]

During the first observation run the LIGO collaboration needed to offload some of its most, intense CPU workflows from its dedicated computing sites to opportunistic resources. Open Science Grid enabled LIGO to run PyCbC, RIFT and Bayeswave workflows to seamlessly run in a combination of owned and opportunistic resources. One of the challenges is enabling the workflows to use several heterogeneous resources in a coordinated and effective way.

We introduce deep learning time-series forecasting for gravitational wave detection of binary neutron star mergers. This method enables the identification of these signals in real advanced LIGO data up to 30 seconds before merger. When applied to GW170817, our deep learning forecasting method identifies the presence of this gravitational wave signal 10 seconds before merger. This novel approach requires a single GPU for inference, and may be used as part of an early warning system for time-sensitive multi-messenger searches.

The birth of gravitational wave astronomy was triggered by the first detection of a signal produced by the merger of two compact objects (also known as a compact binary coalescence event). The following detections made by the Earth-based network of advanced interferometers had a significant impact in many fields of science: astrophysics, cosmology, nuclear physics and fundamental physics. However, compact binary coalescence signals are not the only type of gravitational waves potentially detectable by LIGO, Virgo, and KAGRA. An interesting family of still undetected signals, and the ones that are considered in this review, are the so-called continuous waves, paradigmatically exemplified by the gravitational radiation emitted by galactic, fast-spinning isolated neutron stars with a certain degree of asymmetry in their mass distribution. In this work, I will review the status and the latest results from the analyses of advanced detector data.

Since the early stages of operation of ground-based gravitational-wave interferometers, careful monitoring of these detectors has been an important component of their successful operation and observations. Characterization of gravitational-wave detectors blends computational and instrumental methods of investigating the detector performance. These efforts focus both on identifying ways to improve detector sensitivity for future observations and understand the non-idealized features in data that has already been recorded. Alongside a focus on the detectors themselves, detector characterization includes careful studies of how astrophysical analyses are affected by different data quality issues. This article presents an overview of the multifaceted aspects of the characterization of interferometric gravitational-wave detectors, including investigations of instrumental performance, characterization of interferometer data quality, and the identification and mitigation of data quality issues that impact analysis of gravitational-wave events. Looking forward, we discuss efforts to adapt current detector characterization methods to meet the changing needs of gravitational-wave astronomy.

Gravitational-wave astronomy started in earnest in 2015 with the first observation of waves from a binary black hole merger by NSF's LIGO detectors. Since that time, the signals from many colliding compact objects have been observed with LIGO and Virgo, giving insights into the demographics of stellar black holes, the nature of neutron stars and the products of their coalescence. Detailed studies of the signals are in agreement with the predictions of General Relativity. The instruments which enabled these measurements are of extraordinary sensitivity, and the treatment of the data to enable the observational science requires a deep understanding of the instruments and best practices for analysis. The field is rich with future opportunities to participate in this broad swath of science. [ABSTRACT FROM AUTHOR]

The recent Nobel-prize-winning detections of gravitational waves from merging black holes and the subsequent detection of the collision of two neutron stars in coincidence with electromagnetic observations have inaugurated a new era of multimessenger astrophysics. To enhance the scope of this emergent field of science, we pioneered the use of deep learning with convolutional neural networks, that take time-series inputs, for rapid detection and characterization of gravitational wave signals. This approach, Deep Filtering, was initially demonstrated using simulated LIGO noise. In this article, we present the extension of Deep Filtering using real data from LIGO, for both detection and parameter estimation of gravitational waves from binary black hole mergers using continuous data streams from multiple LIGO detectors. We demonstrate for the first time that machine learning can detect and estimate the true parameters of real events observed by LIGO. Our results show that Deep Filtering achieves similar sensitivities and lower errors compared to matched-filtering while being far more computationally efficient and more resilient to glitches, allowing real-time processing of weak time-series signals in non-stationary non-Gaussian noise with minimal resources, and also enables the detection of new classes of gravitational wave sources that may go unnoticed with existing detection algorithms. This unified framework for data analysis is ideally suited to enable coincident detection campaigns of gravitational waves and their multimessenger counterparts in real-time.

The stochastic gravitational wave background produced by supernovas, magnetars, and merger of binaries constituted of a pair of compact objects is reviewed and updated. The merger of systems composed of two black holes dominates by far the background signal, whose amplitude in the range 10–100 Hz is above the sensitivity of the planned Einstein laser interferometer (ET). The background signal at 25 Hz estimated by the laser interferometric gravitational observatory (LIGO)‐VIRGO collaboration, based on the available merger detection data, is in good agreement with the present theoretical predictions. [ABSTRACT FROM AUTHOR]

Gravitational waves from mergers of black holes and neutron stars are now being detected by LIGO. Here we look at a new source of gravitational waves, i.e., a class of dark matter objects whose properties were earlier elaborated. We show that the frequency of gravitational waves and strains on the detectors from such objects (including their mergers) could be within the sensitivity range of LIGO. The gravitational waves from the possible mergers of these dark matter objects will be different from those produced by neutron star mergers in the sense that they will not be accompanied by electromagnetic radiation since dark matter does not couple with radiation. [ABSTRACT FROM AUTHOR]

The suspended test masses of gravitational-wave (GW) detectors require precise alignment to be able to operate the detector stably and with high sensitivity. This includes the continuous counter-acting of seismic disturbances, which, below a few Hertz, are not sufficiently reduced by the seismic isolation system. The residual angular motion of suspended test masses is further suppressed by the Angular Sensing and Control (ASC) system. However, in doing so, the angular motion can be enhanced by the ASC at higher frequencies where the seismic isolation system is very effective. This has led to sensitivity limitations between about 10 Hz and 25 Hz of the LIGO detectors in past observation runs. The observed ASC noise was larger than simple models predict, which means that more accurate detector models and new simulation tools are required. In this article, we present Lightsaber, a new time-domain simulator of the ASC in LIGO. Lightsaber is a nonlinear simulation of the optomechanical system consisting of the high-power cavity laser beam and the last two stages of suspension in LIGO including the ASC. The main noise inputs are power fluctuations of the laser beam at the input of the arm cavities, read-out noise of sensors used for the ASC, displacement noise from the suspension platforms, and noise introduced by the suspension damping loops. While the plant simulation uses local degrees of freedom of individual suspension systems, the control is applied on a global angular basis, which requires a conversion between the local and global bases for sensing and actuation. Some of the studies that can be done with this simulation concern mis-centering of the beam-spot (BS) position on the test masses, the role of laser power fluctuations for angular dynamics, and the role of the various nonlinear dynamics. The next important step following this work will be a detailed comparison between Lightsaber results and data from the control channels of the LIGO detectors.