arXiv subjects

Stephen Fairhurst

Publications and source records attributed to Stephen Fairhurst.

At least 55 records · Page 3Linked to original sources

arXiv2010

A targeted coherent search for gravitational waves from compact binary coalescences

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 and on data from LIGO's fourth science run and verify that the signal consistency tests are capable of removing the majority of noise transients and the search gives an efficiency comparable to that achieved in Gaussian noise.

gr-qc↗

arXiv2009

Triangulation of gravitational wave sources with a network of detectors

There is significant benefit to be gained by pursuing multi-messenger astronomy with gravitational wave and electromagnetic observations. In order to undertake electromagnetic follow-ups of gravitational wave signals, it will be necessary to accurately localize them in the sky. Since gravitational wave detectors are not inherently pointing instruments, localization will occur primarily through triangulation with a network of detectors. We investigate the expected timing accuracy for observed signals and the consequences for localization. In addition, we discuss the effect of systematic uncertainties in the waveform and calibration of the instruments on the localization of sources. We provide illustrative results of timing and localization accuracy as well as systematic effects for coalescing binary waveforms.

gr-qc↗

arXiv2009

Current status of gravitational-wave observations

The first generation of gravitational wave interferometric detectors has taken data at, or close to, their design sensitivity. This data has been searched for a broad range of gravitational wave signatures. An overview of gravitational wave search methods and results are presented. Searches for gravitational waves from unmodelled burst sources, compact binary coalescences, continuous wave sources and stochastic backgrounds are discussed.

gr-qc↗

arXiv2009

Testing gravitational-wave searches with numerical relativity waveforms: Results from the first Numerical INJection Analysis (NINJA) project

The Numerical INJection Analysis (NINJA) project is a collaborative effort between members of the numerical relativity and gravitational-wave data analysis communities. The purpose of NINJA is to study the sensitivity of existing gravitational-wave search algorithms using numerically generated waveforms and to foster closer collaboration between the numerical relativity and data analysis communities. We describe the results of the first NINJA analysis which focused on gravitational waveforms from binary black hole coalescence. Ten numerical relativity groups contributed numerical data which were used to generate a set of gravitational-wave signals. These signals were injected into a simulated data set, designed to mimic the response of the Initial LIGO and Virgo gravitational-wave detectors. Nine groups analysed this data using search and parameter-estimation pipelines. Matched filter algorithms, un-modelled-burst searches and Bayesian parameter-estimation and model-selection algorithms were applied to the data. We report the efficiency of these search methods in detecting the numerical waveforms and measuring their parameters. We describe preliminary comparisons between the different search methods and suggest improvements for future NINJA analyses.

gr-qc↗

arXiv2009

Status of NINJA: the Numerical INJection Analysis project

The 2008 NRDA conference introduced the Numerical INJection Analysis project (NINJA), a new collaborative effort between the numerical relativity community and the data analysis community. NINJA focuses on modeling and searching for gravitational wave signatures from the coalescence of binary system of compact objects. We review the scope of this collaboration and the components of the first NINJA project, where numerical relativity groups shared waveforms and data analysis teams applied various techniques to detect them when embedded in colored Gaussian noise.

gr-qc↗

arXiv2009

The Mock LISA Data Challenges: from Challenge 1B to Challenge 3

The Mock LISA Data Challenges are a programme to demonstrate and encourage the development of LISA data-analysis capabilities, tools and techniques. At the time of this workshop, three rounds of challenges had been completed, and the next was about to start. In this article we provide a critical analysis of entries to the latest completed round, Challenge 1B. The entries confirm the consolidation of a range of data-analysis techniques for Galactic and massive--black-hole binaries, and they include the first convincing examples of detection and parameter estimation of extreme--mass-ratio inspiral sources. In this article we also introduce the next round, Challenge 3. Its data sets feature more realistic waveform models (e.g., Galactic binaries may now chirp, and massive--black-hole binaries may precess due to spin interactions), as well as new source classes (bursts from cosmic strings, isotropic stochastic backgrounds) and more complicated nonsymmetric instrument noise.

gr-qc↗

arXiv2009

Searching for binary coalescences with inspiral templates: Detection and parameter estimation

There has been remarkable progress in numerical relativity recently. This has led to the generation of gravitational waveform signals covering what has been traditionally termed the three phases of the coalescence of a compact binary - the inspiral, merger and ringdown. In this paper, we examine the usefulness of inspiral only templates for both detection and parameter estimation of the full coalescence waveforms generated by numerical relativity simulations. To this end, we deploy as search templates waveforms based on the effective one-body waveforms terminated at the light-ring as well as standard post-Newtonian waveforms. We find that both of these are good for detection of signals. Parameter estimation is good at low masses, but degrades as the mass of the binary system increases.

gr-qc↗

arXiv2008

Extremality conditions for isolated and dynamical horizons

A maximally rotating Kerr black hole is said to be extremal. In this paper we introduce the corresponding restrictions for isolated and dynamical horizons. These reduce to the standard notions for Kerr but in general do not require the horizon to be either stationary or rotationally symmetric. We consider physical implications and applications of these results. In particular we introduce a parameter e which characterizes how close a horizon is to extremality and should be calculable in numerical simulations.

gr-qc↗

arXiv2008

Host Galaxies Catalog Used in LIGO Searches for Compact Binary Coalescence Events

An up-to-date catalog of nearby galaxies considered as hosts of binary compact objects is provided with complete information about sky position, distance, extinction-corrected blue luminosity and error estimates. With our current understanding of binary evolution, rates of formation and coalescence for binary compact objects scale with massive-star formation and hence the (extinction-corrected) blue luminosity of host galaxies. Coalescence events in binary compact objects are among the most promising gravitational-wave sources for ground-based gravitational-wave detectors such as LIGO. Our catalog and associated error estimates are important for the interpretation of analyses, carried out for LIGO, to constrain the rates of compact binary coalescence, given an astrophysical population model for the sources considered. We discuss how the notion of effective distance, created to account for the antenna pattern of a gravitational-wave detector, must be used in conjunction with our catalog. We note that the catalog provided can be used on other astronomical analysis of populations that scale with galaxy blue luminosity.

astro-ph↗

arXiv2007

Report on the second Mock LISA Data Challenge

The Mock LISA Data Challenges are a program to demonstrate LISA data-analysis capabilities and to encourage their development. Each round of challenges consists of several data sets containing simulated instrument noise and gravitational-wave sources of undisclosed parameters. Participants are asked to analyze the data sets and report the maximum information about source parameters. The challenges are being released in rounds of increasing complexity and realism: in this proceeding we present the results of Challenge 2, issued in January 2007, which successfully demonstrated the recovery of signals from supermassive black-hole binaries, from ~20,000 overlapping Galactic white-dwarf binaries, and from the extreme-mass-ratio inspirals of compact objects into central galactic black holes.

gr-qc↗

arXiv2007

The Loudest Event Statistic: General Formulation, Properties and Applications

The use of the loudest observed event to generate statistical statements about rate and strength has become standard in searches for gravitational waves from compact binaries and pulsars. The Bayesian formulation of the method is generalized in this paper to allow for uncertainties both in the background estimate and in the properties of the population being constrained. The method is also extended to allow rate interval construction. Finally, it is shown how to combine the results from multiple experiments and a comparison is drawn between the upper limit obtained in a single search and the upper limit obtained by combining the results of two experiments each of half the original duration. To illustrate this, we look at an example case, motivated by the search for gravitational waves from binary inspiral.

gr-qc↗

arXiv2007

Interpreting the results of searches for gravitational waves from coalescing binaries

We introduce a method based on the loudest event statistic to calculate an upper limit or interval on the astrophysical rate of binary coalescence. The calculation depends upon the sensitivity and noise background of the detectors, and a model for the astrophysical distribution of coalescing binaries. There are significant uncertainties in the calculation of the rate due to both astrophysical and instrumental uncertainties as well as errors introduced by using the post--Newtonian waveform to approximate the full signal. We catalog these uncertainties in detail and describe a method for marginalizing over them. Throughout, we provide an example based on the initial LIGO detectors.

gr-qc↗

arXiv2007

Searching for Gravitational Waves from Binary Inspirals with LIGO

We describe the current status of the search for gravitational waves from inspiralling compact binary systems in LIGO data. We review the result from the first scientific run of LIGO (S1). We present the goals of the search of data taken in the second scientific run (S2) and describe the differences between the methods used in S1 and S2.

gr-qc↗

arXiv2007

Isolated, slowly evolving, and dynamical trapping horizons: geometry and mechanics from surface deformations

We study the geometry and dynamics of both isolated and dynamical trapping horizons by considering the allowed variations of their foliating two-surfaces. This provides a common framework that may be used to consider both their possible evolutions and their deformations as well as derive the well-known flux laws. Using this framework, we unify much of what is already known about these objects as well as derive some new results. In particular we characterize and study the "almost-isolated" trapping horizons known as slowly evolving horizons. It is for these horizons that a dynamical first law holds and this is analogous and closely related to the Hawking-Hartle formula for event horizons.

gr-qc↗

arXiv2005

Horizon energy and angular momentum from a Hamiltonian perspective

Classical black holes and event horizons are highly non-local objects, defined in terms of the causal past of future null infinity. Alternative, (quasi)local definitions are often used in mathematical, quantum, and numerical relativity. These include apparent, trapping, isolated, and dynamical horizons, all of which are closely associated to two-surfaces of zero outward null expansion. In this paper we show that three-surfaces which can be foliated with such two-surfaces are suitable boundaries in both a quasilocal action and a phase space formulation of general relativity. The resulting formalism provides expressions for the quasilocal energy and angular momentum associated with the horizon. The values of the energy and angular momentum are in agreement with those derived from the isolated and dynamical horizon frameworks.

gr-qc↗

arXiv2005

Status of the joint LIGO--TAMA300 inspiral analysis

We present the status of the joint search for gravitational waves from inspiraling neutron star binaries in the LIGO Science Run 2 and TAMA300 Data Taking Run 8 data, which was taken from February 14 to April 14, 2003, by the LIGO and TAMA collaborations. In this paper we discuss what has been learned from an analysis of a subset of the data sample reserved as a ``playground''. We determine the coincidence conditions for parameters such as the coalescence time and chirp mass by injecting simulated Galactic binary neutron star signals into the data stream. We select coincidence conditions so as to maximize our efficiency of detecting simulated signals. We obtain an efficiency for our coincident search of 78 %, and show that we are missing primarily very distant signals for TAMA300. We perform a time slide analysis to estimate the background due to accidental coincidence of noise triggers. We find that the background triggers have a very different character from the triggers of simulated signals.

gr-qc↗

arXiv2004

Plans for the LIGO-TAMA Joint Search for Gravitational Wave Bursts

We describe the plans for a joint search for unmodelled gravitational wave bursts being carried out by the LIGO and TAMA collaborations using data collected during February-April 2003. We take a conservative approach to detection, requiring candidate gravitational wave bursts to be seen in coincidence by all four interferometers. We focus on some of the complications of performing this coincidence analysis, in particular the effects of the different alignments and noise spectra of the interferometers.

gr-qc↗

arXiv2004

The first law for slowly evolving horizons

We study the mechanics of Hayward's trapping horizons, taking isolated horizons as equilibrium states. Zeroth and second laws of dynamic horizon mechanics come from the isolated and trapping horizon formalisms respectively. We derive a dynamical first law by introducing a new perturbative formulation for dynamic horizons in which "slowly evolving" trapping horizons may be viewed as perturbatively non-isolated.

gr-qc↗