We introduce a fully-coherent method for searching for gravitational wave signals generated by the merger of black hole and/or neutron star binaries. This extends the coherent analysis previously developed and used for targeted gravitational wave searches to an all-sky, all-time search. We apply the search to one month of data taken during the fifth science run of the LIGO detectors. We demonstrate an increase in sensitivity of 25% over the coincidence search, which is commensurate with expectations. Finally, we discuss prospects for implementing and running a coherent search for gravitational wave signals from binary coalescence in the advanced gravitational wave detector data.
Fully-coherent all-sky search for gravitational wave (GW) signals from the coalescence of compact object binaries is a computationally expensive task. Approximations, such as semi-coherent coincidence searches, are currently used to circumvent the computational barrier with a concomitant loss in sensitivity. We explore the effectiveness of Particle Swarm Optimization (PSO) in addressing this problem. Our results, using a simulated network of detectors with initial LIGO design sensitivities and a realistic signal strength, show that PSO can successfully deliver a fully-coherent all-sky search w…
We compute the two-dimensional correlation functions of the binary black hole coalescence detections in LIGO-Virgo's first and second observation runs. The sky distribution of binary black hole coalescence events is tested for correlations at different angular scales by comparing the observed correlation function to two reference functions that are obtained from mock datasets of localization error regions uniformly distributed in the sky. No excess correlation at any angular scale is found. The power-law slope of the correlation function is estimated to be $γ= 2.24\pm 0.33$ at the three-$σ$ co…
In this paper we present a method for conducting a coherent search for single spin compact binary coalescences in gravitational wave data and compare this search to the existing coincidence method for single spin searches. We propose a method to characterize the regions of the parameter space where the single spin search, both coincident and coherent, will increase detection efficiency over the existing non-precessing search. We also show example results of the coherent search on a stretch of data from LIGO's fourth science run but note that a set of signal based vetoes will be needed before t…
In this article, we revisit the problem of coherent multi-detector search of gravitational wave from compact binary coalescence with Neutron stars and Black Holes using advanced interferometers like LIGO-Virgo. Based on the loss of optimal multi-detector signal-to-noise ratio (SNR), we construct a hybrid statistic as a best of maximum-likelihood-ratio(MLR) statistic tuned for face-on and face-off binaries. The statistical properties of the hybrid statistic is studied. The performance of this hybrid statistic is compared with that of the coherent MLR statistic for generic inclination angles. Ow…
We present the details of a method for conducting a targeted, coherent search for compact binary coalescences. The search is tailored to be used as a followup to electromagnetic transients such as Gamma Ray Bursts. We derive the coherent search statistic for Gaussian detector noise and discuss the benefits of a coherent, multi-detector search over coincidence methods. To mitigate the effects of non-stationary data, we introduce a number of signal consistency tests, including the null SNR, amplitude consistency and several $χ^{2}$ tests. We demonstrate the search performance on Gaussian noise a…
A leading candidate source of detectable gravitational waves is the inspiral and merger of pairs of stellar-mass compact objects. The advanced LIGO and advanced Virgo detectors will allow scientists to detect inspiral signals from more massive systems and at earlier times in the detector band, than with first generation detectors. The signal from a coalescence of two neutron stars is expected to stay in the sensitive band of advanced detectors for several minutes, thus allowing detection before the final coalescence of the system. In this work, the prospects of detecting inspiral signals prior…
We investigate the use of particle swarm optimization (PSO) algorithm for detection of gravitational-wave signals from compact binary coalescences. We show that the PSO is fast and effective in searching for gravitational wave signals. The PSO-based aligned-spin coincident multi-detector search recovers appreciably more gravitational-wave signals, for a signal-to-noise ratio (SNR) of 10, the PSO based aligned-spin search recovers approximately 26 $\%$ more events as compared to the template bank searches. The PSO-based aligned-spin coincident search uses 48k matched-filtering operations, and p…
Short, hard gamma-ray bursts (GRBs) are believed to originate from the coalescence of two neutron stars (NSs) or a NS and a black hole (BH). If this scenario is correct, then short GRBs will be accompanied by the emission of strong gravitational waves (GWs), detectable by GW observatories such as LIGO, Virgo, KAGRA, and LIGO-India. As compared with blind, all-sky, all-time GW searches, externally triggered searches for GW counterparts to short GRBs have the advantages of both significantly reduced detection threshold due to known time and sky location and enhanced GW amplitude because of face-…
While a fully-coherent all-sky search is known to be optimal for detecting gravitational wave signals from compact binary coalescences, its high computational cost has limited current searches to less sensitive coincidence-based schemes. Following up on previous work that has demonstrated the effectiveness of Particle Swarm Optimization in reducing the computational cost of this search, we present an implementation that achieves near real-time computational speed. This is achieved by combining the search efficiency of PSO with a significantly revised and optimized numerical implementation of t…
Advanced ground-based gravitational-wave (GW) detectors begin operation imminently. Their intended goal is not only to make the first direct detection of GWs, but also to make inferences about the source systems. Binary neutron-star mergers are among the most promising sources. We investigate the performance of the parameter-estimation \edit{(PE)} pipeline that will be used during the first observing run of the Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO) in 2015: we concentrate on the ability to reconstruct the source location on the sky, but also consider the ability …
This paper presents the SPIIR pipeline used for public alerts during the third advanced LIGO and Virgo observation run (O3 run). The SPIIR pipeline uses infinite impulse response (IIR) filters to perform extremely low-latency matched filtering and this process is further accelerated with graphics processing units (GPUs). It is the first online pipeline to select candidates from multiple detectors using a coherent statistic based on the maximum network likelihood ratio statistic principle. Here we simplify the derivation of this statistic using the singular-value-decomposition (SVD) technique a…
Next-generation global gravitational-wave detector network: Impact of detector orientation on compact binary coalescence and stochastic gravitational-wave background searches
Gravitational-wave (GW) detections of binary neutron star coalescences play a crucial role to constrain the microscopic interaction of matter at ultrahigh density. Similarly, if boson stars exist in the universe their coalescence can be used to constrain the fundamental coupling constants of a scalar field theory. We develop the first coherent waveform model for the inspiral of boson stars with quartic interactions. The waveform includes coherently spin-induced quadrupolar and tidal-deformability contributions in terms of the masses and spins of the binary and of a single coupling constant of …
Compact binary coalescences are a promising source of gravitational waves for second-generation interferometric gravitational-wave detectors. Although matched filtering is the optimal search method for well-modeled systems, alternative detection strategies can be used to guard against theoretical errors (e.g., involving new physics and/or assumptions about spin/eccentricity) while providing a measure of redundancy. In previous work, we showed how "seedless clustering" can be used to detect long-lived gravitational-wave transients in both targeted and all-sky searches. In this paper, we apply s…
The planned Laser Interferometric Space Antenna (LISA) will be able to detect gravitational waves (GWs) from intermediate mass binary black holes (IMBBHs) in the mass range $\sim 10^{2} \mbox{-} 10^{4}\,M_{\odot}$ up to a redshift $z\sim20$. Modulation effects due to orbital motion of LISA around the Sun facilitate precise premerger localization of the sources, which in turn would help in electromagnetic (EM) followups. In this work, we calculate the uncertainties in sky position, luminosity distance, and time of coalescence as a function of time to coalescence. For representative masses of th…
Localization estimates for GW150914, the first binary black hole detected by the LIGO instruments, were shared with partner facilities for electromagnetic follow-up. While the source was a compact binary coalescence (CBC), it was first identified by algorithms that search for unmodeled signals, which produced the skymaps that directed electromagnetic observations. Later on, CBC specific algorithms produced refined versions, which showed significant differences. In this paper we show that those differences were not accidental and that CBC and unmodeled skymaps for binary black holes will freque…
Global network of advanced Interferometric gravitational wave (GW) detectors are expected to be on-line soon. Coherent observation of GW from a distant compact binary coalescence (CBC) with a network of interferometers located in different continents give crucial information about the source such as source location and polarization information. In this paper we compare different multi-detector network detection statistics for CBC search. In maximum likelihood ratio (MLR) based detection approaches, the likelihood ratio is optimized to obtain the best model parameters and the best likelihood ra…
The coherent WaveBurst (cWB) pipeline implements a minimally-modelled search to find a coherent response in the network of gravitational wave detectors of the LIGO-Virgo Collaboration in the time-frequency domain. In this manuscript, we provide a timely introduction to an extension of the cWB analysis to detect spectral features beyond the main quadrupolar emission of gravitational waves during the inspiral phase of compact binary coalescences; more detailed discussion will be provided in a forthcoming paper [1]. The search is performed by defining specific regions in the time-frequency map to…
The gravitational wave detectors currently in operation perform the analysis of their scientific data jointly. Concerning the search for bursting sources, coherent data analysis methods have been shown to be more efficient. In the coherent approach, the data collected by the detectors are time-shifted and linearly combined so that the signatures received by each detector add up constructively (thus improving the resulting signal-to-noise ratio). This operation has to be performed over a sky grid (which determines the sky locations to be searched). A limitation of those pipelines is their large…
We present a method for coherently combining short data segments from gravitational-wave detectors to improve the sensitivity of semi-coherent searches for continuous gravitational waves. All-sky searches for continuous gravitational waves from unknown sources are computationally limited. The semi-coherent approach reduces the computational cost by dividing the entire observation timespan into short segments to be analyzed coherently, then combined together incoherently. Semi-coherent analyses that attempt to improve sensitivity by coherently combining data from multiple detectors face a compu…
Gravitational waves from binary neutron star mergers can be used as alerts to enable prompt follow-up observations. In particular, capturing prompt electromagnetic and astroparticle emissions from the moment of a binary merger presents unique constraints on the time scale and sky localization for online gravitational wave detection. Here we present the expected performance of the SPIIR online detection pipeline that is designed for this purpose in the upcoming international LIGO-Virgo's 4th Science Run (O4). Using simulated Gaussian data for the two LIGO observatories with expected O4 sensitiv…
Gravitational waves in general relativity contain two polarization degrees of freedom, commonly labeled plus and cross. Besides those two tensor modes, generic theories of gravity predict up to four additional polarization modes: two scalar and two vector. Detection of nontensorial modes in gravitational wave data would constitute a clean signature of physics beyond general relativity. Previous measurements have pointed to the unambiguous presence of tensor modes in gravitational waves, but the presence of additional generic nontensorial modes has not been directly tested. We propose a model-i…
2015 will see the first observations of Advanced LIGO and the start of the gravitational-wave (GW) advanced-detector era. One of the most promising sources for ground-based GW detectors are binary neutron-star (BNS) coalescences. In order to use any detections for astrophysics, we must understand the capabilities of our parameter-estimation analysis. By simulating the GWs from an astrophysically motivated population of BNSs, we examine the accuracy of parameter inferences in the early advanced-detector era. We find that sky location, which is important for electromagnetic follow-up, can be det…
We describe the implementation of a search for gravitational waves from compact binary coalescences in LIGO and Virgo data. This all-sky, all-time, multi-detector search for binary coalescence has been used to search data taken in recent LIGO and Virgo runs. The search is built around a matched filter analysis of the data, augmented by numerous signal consistency tests designed to distinguish artifacts of non-Gaussian detector noise from potential detections. We demonstrate the search performance using Gaussian noise and data from the fifth LIGO science run and demonstrate that the signal cons…
Standard detection and analysis techniques for transient gravitational waves make the assumption that detector data contains, at most, one signal at any time. As detectors improve in sensitivity, this assumption will no longer be valid. In this paper we examine how current search techniques for transient gravitational waves will behave under the presence of more than one signal. We perform searches on data sets containing time-overlapping compact binary coalescences. This includes a modelled, matched filter search (PyCBC), and an unmodelled coherent search, coherent WaveBurst (cWB). Both of th…
In this review we examine the amplitude intensity associated to tensorial and non-tensorial polarization modes generated by binary systems at their inspiral stage, within the alternative theories of gravity of Brans Dicke, Rosen, and Lightman Lee. This study is performed without making an explicit use of the Transverse Traceless gauge of the General Relativity approach, and at the Newtonian limit. Consequently such additional polarization modes appear (non-tensorial) due to additional degrees of freedom in modified theories of gravitation. We model and compare the different polarization modes …
While a fully-coherent all-sky search is known to be optimal for detecting signals from compact binary coalescences (CBCs), its high computational cost has limited current searches to less sensitive coincidence-based schemes. For a network of first generation GW detectors, it has been demonstrated that Particle Swarm Optimization (PSO) can reduce the computational cost of this search, in terms of the number of likelihood evaluations, by a factor of $\approx 10$ compared to a grid-based optimizer. Here, we extend the PSO-based search to a network of second generation detectors and present furth…
Rapid parameter estimation of gravitational waves from binary neutron star coalescence, in particular accurate sky localisation in minutes after the initial detection stage, is crucial for the success of multi-messenger observations. One of the techniques to speed up the parameter estimation, which has been applied for the production analysis of the LIGO-Virgo collaboration, is reduced order quadrature (ROQ). While it speeds up parameter estimation significantly, the time required is still on the order of hours. Focusing on the fact that the parameter-estimation follow-up can be tuned with the…
In connection with the possibility of skyrmion production from small domain disoriented chiral condensates formation from heavy ion collisions, the direct relation of a classical skyrmion to baryon states is examined. It is argued that a skyrmion is a coherent state of baryons. The collective coordinate approach of quantization means that the physical baryon states exist not in flat space but on a compact manifold. This requires the construction of coherent states in such a curve space. Using the techniques associated with the Segal-Bargmann transform also known as the coherent state transform…
All-sky, broadband, coherent searches for gravitational-wave pulsars are restricted by limited computational resources. Minimizing the number of templates required to cover the search parameter space, of sky position and frequency evolution, is one important way to reduce the computational cost of a search. We demonstrate a practical algorithm which, for the first time, achieves template placement with a minimal number of templates for an all-sky search, using the reduced supersky parameter-space metric of Wette and Prix [Phys. Rev. D 88, 123005 (2013)]. The metric prescribes a constant templa…
In this paper, we investigate the morphology of the events from the GWTC-1 catalog of compact binary coalescences as reconstructed by a method based on coherent excess power: we use an open-source version of the coherent WaveBurst (cWB) analysis pipeline, which does not make use of waveform models. The coherent response of the LIGO-Virgo network of detectors is estimated by using loose bounds on the duration and bandwidth of the signal. This pipeline version reproduces the same results that are reported for cWB in recent publications by the LIGO and Virgo collaborations. In particular, the sky…
We present the first application of deep learning forecasting for binary neutron stars, neutron star - black hole systems, and binary black hole mergers that span an eccentricity range e <= 0.9. We train neural networks that describe these astrophysical populations, and then test their performance by injecting simulated eccentric signals in advanced LIGO noise available at the \texttt{Gravitational Wave Open Science Center} to: 1) quantify how fast neural networks identify these signals before the binary components merge; 2) quantify how accurately neural networks estimate the time to merger o…
Coherent WaveBurst is a generic, multidetector gravitational wave burst search based on the excess power approach. The coherent WaveBurst algorithm currently employed in the all-sky short-duration gravitational wave burst search uses a conditional approach on selected attributes in the multidimensional event attribute space to distinguish between noisy events from that of astrophysical origin. We have been developing a supervised machine learning approach based on the Gaussian mixture modeling to model the attribute space for signals as well as noise events to enhance the probability of burst …
Rapid sky localization of gravitational wave sources is crucial to enable prompt electromagnetic follow-ups. In this article, we present a novel semianalytical approach for sky localization of gravitational waves from compact binary coalescences. We use the Bayesian framework with an analytical approximation to the prior distributions for a given astrophysical model. We derive a semianalytical solution to the posterior distribution of source directions. This method only requires one-fold numerical integral that marginalizes over the merger time, compared to the five-fold numerical integration …
We present a general framework for incorporating astrophysical information into Bayesian parameter estimation techniques used by gravitational wave data analysis to facilitate multi-messenger astronomy. Since the progenitors of transient gravitational wave events, such as compact binary coalescences, are likely to be associated with a host galaxy, improvements to the source sky location estimates through the use of host galaxy information are explored. To demonstrate how host galaxy properties can be included, we simulate a population of compact binary coalescences and show that for ~8.5% of s…
We introduce a highly-parallelizable architecture for estimating parameters of compact binary coalescence using gravitational-wave data and waveform models. Using a spherical harmonic mode decomposition, the waveform is expressed as a sum over modes that depend on the intrinsic parameters (e.g. masses) with coefficients that depend on the observer dependent extrinsic parameters (e.g. distance, sky position). The data is then prefiltered against those modes, at fixed intrinsic parameters, enabling efficiently evaluation of the likelihood for generic source positions and orientations, independen…
We present results of an all-sky search in the Parkes Pulsar Timing Array (PPTA) Data Release 1 data set for continuous gravitational waves (GWs) in the frequency range from $5\times 10^{-9}$ to $2\times 10^{-7}$ Hz. Such signals could be produced by individual supermassive binary black hole systems in the early stage of coalescence. We phase up the pulsar timing array data set to form, for each position on the sky, two data streams that correspond to the two GW polarizations and then carry out an optimal search for GW signals on these data streams. Since no statistically significant GWs were …
A torsion-bar antenna (TOBA) is a low-frequency terrestrial gravitational wave (GW) antenna which consists of two orthogonal bar-shaped test masses. We upgraded the prototype TOBA and achieved the strain sensitivity $10^{-10}$ Hz$^{-1/2}$ at around 1 Hz. We operated the upgraded TOBA (called the "Phase-II TOBA") located at Tokyo in Japan for 22.5 hours and performed an all-sky coherent search for continuous GWs using the $\mathcal{F}$-statistic. We place upper limits on continuous GWs from electromagnetically unknown sources in the frequency range from 6 Hz to 7 Hz with the first derivative of…
The sensitivity of all-sky searches for gravitational-wave pulsars is primarily limited by the finite availability of computing resources. Semicoherent searches are a widely-used method of maximizing sensitivity to gravitational-wave pulsars at fixed computing cost: the data from a gravitational-wave detector are partitioned into a number of segments, each segment is coherently analyzed, and the analysis results from each segment are summed together. The generation of template banks for the coherent analysis of each segment, and for the summation, requires knowledge of the metrics associated w…
With multiple observatories and missions being planned for detecting orphaned afterglows associated with gamma-ray bursts (GRBs) we emphasize the importance of developing data analysis strategies for searching their possible counterpart signals in the data of gravitational wave (GW) detectors in the advanced detector era. This is especially attractive since short hard gamma-ray bursts (SGRBs) may have compact binary coalescences involving neutron stars (CBCNSs) as their progenitors, which emit gravitational waves. Joint electromagnetic (EM) and GW observations of these objects will enrich our …
Continuous gravitational-wave (CW) signals such as emitted by spinning neutron stars are an important target class for current detectors. However, the enormous computational demand prohibits fully coherent broadband all-sky searches for prior unknown CW sources over wide ranges of parameter space and for yearlong observation times. More efficient hierarchical "semicoherent" search strategies divide the data into segments much shorter than one year, which are analyzed coherently; then detection statistics from different segments are combined incoherently. To optimally perform the incoherent com…
All-sky, broadband, coherent searches for gravitational-wave pulsars are computationally limited. It is therefore important to make efficient use of available computational resources, notably by minimizing the number of templates used to cover the signal parameter space of sky position and frequency evolution. For searches over the sky, however, the required template density (determined by the parameter-space metric) is different at each sky position, which makes it difficult in practice to achieve an efficient covering. Previous work on this problem has found various choices of sky and freque…
We discuss the Anderson localization of electromagnetic fields in the fluctuating plasma induced by the gravitational density perturbation before the recombination time of the Universe. Randomly distributed localized coherent electromagnetic fields emerge in the thermal equilibrium before the recombination time. We argue that the localized coherent electric fields eventually produce cosmological magnetic fields after the decoupling time.
In this paper, we study an application of deep learning to the advanced LIGO and advanced Virgo coincident detection of gravitational waves (GWs) from compact binary star mergers. This deep learning method is an extension of the Deep Filtering method used by George and Huerta (2017) for multi-inputs of network detectors. Simulated coincident time series data sets in advanced LIGO and advanced Virgo detectors are analyzed for estimating source luminosity distance and sky location. As a classifier, our deep neural network (DNN) can effectively recognize the presence of GW signals when the optima…
Instrumental and environmental transient noise bursts in gravitational-wave detectors, or glitches, may impair astrophysical observations by adversely affecting the sky localization and the parameter estimation of gravitational-wave signals. Denoising of detector data is especially relevant during low-latency operations because electromagnetic follow-up of candidate detections requires accurate, rapid sky localization and inference of astrophysical sources. NNETFIX is a machine learning-based algorithm designed to remove glitches detected in coincidence with transient gravitational-wave signal…
The space of phase-parameters (sky-position, frequency, spindowns) of a coherent matched-filtering search for continuous gravitational waves from isolated neutron stars shows strong global correlations (``circles in the sky''). In the local limit this can be analysed in terms of a parameter-space metric, but the global properties are less well studied. In this work we report on our recent progress in understanding these global correlations analytically for short to intermediate (less than a month, say) observation times and neglecting spindowns. The location of these correlation-circles in par…
The frequencies and phases of emission from extra-solar sources measured by Earth-bound observers are modulated by the motions of the observer with respect to the source, and through relativistic effects. These modulations depend critically on the source's sky-location. Precise knowledge of the modulations are required to coherently track the source's phase over long observations, for example, in pulsar timing, or searches for continuous gravitational waves. The modulations can be modelled as sky-location and time-dependent time delays that convert arrival times at the observer to the inertial…
Gravitational waveforms from the inspiral and ring-down stages of the binary black hole coalescences can be modelled accurately by approximation/perturbation techniques in general relativity. Recent progress in numerical relativity has enabled us to model also the non-perturbative merger phase of the binary black-hole coalescence problem. This enables us to \emph{coherently} search for all three stages of the coalescence of non-spinning binary black holes using a single template bank. Taking our motivation from these results, we propose a family of template waveforms which can model the inspir…
As the Advanced LIGO and Advanced Virgo interferometers, soon to be joined by the KAGRA interferometer, increase their sensitivity, they detect an ever-larger number of gravitational waves with a significant presence of higher multipoles in addition to the dominant $(2, 2)$ multipole. These higher multipoles can be detected with different approaches, such as the minimally-modeled burst search methods, and here we discuss one such approach based on the coherent WaveBurst pipeline (cWB). During the inspiral phase the higher multipoles produce chirps whose instantaneous frequency is a multiple of…
We show that the black hole binary (BHB) coalescence rates inferred from the advanced LIGO (aLIGO) detection of GW150914 imply an unexpectedly loud GW sky at milli-Hz frequencies accessible to the evolving Laser Interferometer Space Antenna (eLISA), with several outstanding consequences. First, up to thousands of BHB will be individually resolvable by eLISA; second, millions of non resolvable BHBs will build a confusion noise detectable with signal-to-noise ratio of few to hundreds; third -- and perhaps most importantly -- up to hundreds of BHBs individually resolvable by eLISA will coalesce i…
Deep Learning Search for Gravitational Waves from Compact Binary Coalescence
Università degli Studi di Urbino Carlo Bo（乌尔比诺卡洛·博大学）；INFN, Sezione di Firenze（意大利国家核物理研究所佛罗伦萨分部）；Université Paris-Saclay, CNRS/IN2P3, IJCLab（巴黎萨克雷大学、法国国家科学研究中心/法国国家粒子物理研究所、IJCLab）
