Publications (326)676.04 Total impact
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ABSTRACT: We report the results of a multimessenger search for coincident signals from the LIGO and Virgo gravitationalwave observatories and the partially completed IceCube highenergy neutrino detector, including periods of joint operation between 20072010. These include parts of the 20052007 run and the 20092010 run for LIGOVirgo, and IceCube's observation periods with 22, 59 and 79 strings. We find no significant coincident events, and use the search results to derive upper limits on the rate of joint sources for a range of source emission parameters. For the optimistic assumption of gravitationalwave emission energy of $10^{2}$ M$_\odot$c$^2$ at $\sim 150$ Hz with $\sim 60$ ms duration, and highenergy neutrino emission of $10^{51}$ erg comparable to the isotropic gammaray energy of gammaray bursts, we limit the source rate below $1.6 \times 10^{2}$ Mpc$^{3}$yr$^{1}$. We also examine how combining information from gravitational waves and neutrinos will aid discovery in the advanced gravitationalwave detector era.07/2014;  [Show abstract] [Hide abstract]
ABSTRACT: We present the results of a search for gravitational waves associated with 223 gammaray bursts (GRBs) detected by the InterPlanetary Network (IPN) in 20052010 during LIGO's fifth and sixth science runs and Virgo's first, second and third science runs. The IPN satellites provide accurate times of the bursts and sky localizations that vary significantly from degree scale to hundreds of square degrees. We search for both a wellmodeled binary coalescence signal, the favored progenitor model for short GRBs, and for generic, unmodeled gravitational wave bursts. Both searches use the event time and sky localization to improve the gravitationalwave search sensitivity as compared to corresponding alltime, allsky searches. We find no evidence of a gravitationalwave signal associated with any of the IPN GRBs in the sample, nor do we find evidence for a population of weak gravitationalwave signals associated with the GRBs. For all IPNdetected GRBs, for which a sufficient duration of quality gravitationalwave data is available, we place lower bounds on the distance to the source in accordance with an optimistic assumption of gravitationalwave emission energy of $10^{2}M_{\odot}c^2$ at 150 Hz, and find a median of 13 Mpc. For the 27 shorthard GRBs we place 90% confidence exclusion distances to two source models: a binary neutron star coalescence, with a median distance of 12Mpc, or the coalescence of a neutron star and black hole, with a median distance of 22 Mpc. Finally, we combine this search with previously published results to provide a population statement for GRB searches in firstgeneration LIGO and Virgo gravitationalwave detectors, and a resulting examination of prospects for the advanced gravitationalwave detectors.Physical Review Letters 06/2014; 113(1):011102. · 7.73 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: Gravitational waves from a variety of sources are predicted to superpose to create a stochastic background. This background is expected to contain unique information from throughout the history of the universe that is unavailable through standard electromagnetic observations, making its study of fundamental importance to understanding the evolution of the universe. We carry out a search for the stochastic background with the latest data from LIGO and Virgo. Consistent with predictions from most stochastic gravitationalwave background models, the data display no evidence of a stochastic gravitationalwave signal. Assuming a gravitationalwave spectrum of Omega_GW(f)=Omega_alpha*(f/f_ref)^alpha, we place 95% confidence level upper limits on the energy density of the background in each of four frequency bands spanning 41.51726 Hz. In the frequency band of 41.5169.25 Hz for a spectral index of alpha=0, we constrain the energy density of the stochastic background to be Omega_GW(f)<5.6x10^6. For the 6001000 Hz band, Omega_GW(f)<0.14*(f/900 Hz)^3, a factor of 2.5 lower than the best previously reported upper limits. We find Omega_GW(f)<1.8x10^4 using a spectral index of zero for 170600 Hz and Omega_GW(f)<1.0*(f/1300 Hz)^3 for 10001726 Hz, bands in which no previous direct limits have been placed. The limits in these four bands are the lowest direct measurements to date on the stochastic background. We discuss the implications of these results in light of the recent claim by the BICEP2 experiment of the detection of inflationary gravitational waves.06/2014; 
Article: First allsky search for continuous gravitational waves from unknown sources in binary systems
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ABSTRACT: We present the first results of an allsky search for continuous gravitational waves from unknown spinning neutron stars in binary systems using LIGO and Virgo data. Using a specially developed analysis program, the TwoSpect algorithm, the search was carried out on data from the sixth LIGO Science Run and the second and third Virgo Science Runs. The search covers a range of frequencies from 20 Hz to 520 Hz, a range of orbital periods from 2 to ~2,254 h and a frequency and perioddependent range of frequency modulation depths from 0.277 to 100 mHz. This corresponds to a range of projected semimajor axes of the orbit from ~0.6e3 ls to ~6,500 ls assuming the orbit of the binary is circular. While no plausible candidate gravitational wave events survive the pipeline, upper limits are set on the analyzed data. The most sensitive 95% confidence upper limit obtained on gravitational wave strain is 2.3e24 at 217 Hz, assuming the source waves are circularly polarized. Although this search has been optimized for circular binary orbits, the upper limits obtained remain valid for orbital eccentricities as large as 0.9. In addition, upper limits are placed on continuous gravitational wave emission from the lowmass xray binary Scorpius X1 between 20 Hz and 57.25 Hz.05/2014;  [Show abstract] [Hide abstract]
ABSTRACT: In this paper we report on a search for shortduration gravitational wave bursts in the frequency range 64 Hz1792 Hz associated with gammaray bursts (GRBs), using data from GEO600 and one of the LIGO or Virgo detectors. We introduce the method of a linear search grid to analyse GRB events with large sky localisation uncertainties such as the localisations provided by the Fermi Gammaray Burst Monitor (GBM). Coherent searches for gravitational waves (GWs) can be computationally intensive when the GRB sky position is not welllocalised, due to the corrections required for the difference in arrival time between detectors. Using a linear search grid we are able to reduce the computational cost of the analysis by a factor of O(10) for GBM events. Furthermore, we demonstrate that our analysis pipeline can improve upon the sky localisation of GRBs detected by the GBM, if a highfrequency GW signal is observed in coincidence. We use the linear search grid method in a search for GWs associated with 129 GRBs observed satellitebased gammaray experiments between 2006 and 2011. The GRBs in our sample had not been previously analysed for GW counterparts. A fraction of our GRB events are analysed using data from GEO600 while the detector was using squeezedlight states to improve its sensitivity; this is the first search for GWs using data from a squeezedlight interferometric observatory. We find no evidence for GW signals, either with any individual GRB in this sample or with the population as a whole. For each GRB we place lower bounds on the distance to the progenitor, assuming a fixed GW emission energy of $10^{2} M_{\odot}c^{2}$, with a median exclusion distance of 0.8 Mpc for emission at 500 Hz and 0.3 Mpc at 1 kHz. The reduced computational cost associated with a linear search grid will enable rapid searches for GWs associated with Fermi GBM events in the Advanced detector era.05/2014; 

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ABSTRACT: This paper reports on an unmodeled, allsky search for gravitational waves from merging intermediate mass black hole binaries (IMBHB). The search was performed on data from the second joint science run of the LIGO and Virgo detectors (July 2009  October 2010) and was sensitive to IMBHBs with a range up to $\sim 200$ Mpc, averaged over the possible sky positions and inclinations of the binaries with respect to the line of sight. No significant candidate was found. Upper limits on the coalescencerate density of nonspinning IMBHBs with total masses between 100 and $450 \ \mbox{M}_{\odot}$ and mass ratios between $0.25$ and $1\,$ were placed by combining this analysis with an analogous search performed on data from the first LIGOVirgo joint science run (November 2005  October 2007). The most stringent limit was set for systems consisting of two $88 \ \mbox{M}_{\odot}$ black holes and is equal to $0.12 \ \mbox{Mpc}^{3} \ \mbox{Myr}^{1}$ at the $90\%$ confidence level. This paper also presents the first estimate, for the case of an unmodeled analysis, of the impact on the search range of IMBHB spin configurations: the visible volume for IMBHBs with nonspinning components is roughly doubled for a population of IMBHBs with spins aligned with the binary's orbital angular momentum and uniformly distributed in the dimensionless spin parameter up to 0.8, whereas an analogous population with antialigned spins decreases the visible volume by $\sim 20\%\,$.04/2014; 
Article: Small mass plunging into a Kerr black hole: Anatomy of the inspiralmergerringdown waveforms
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ABSTRACT: We numerically solve the Teukolsky equation in the time domain to obtain the gravitationalwave emission of a small mass inspiraling and plunging into the equatorial plane of a Kerr black hole. We account for the dissipation of orbital energy using the Teukolsky frequencydomain gravitationalwave fluxes for circular, equatorial orbits, down to the lightring. We consider Kerr spins $0.99 \leq q \leq 0.99$, and compute the inspiralmergerringdown (2,2), (2,1), (3,3), (3,2), (4,4), and (5,5) modes. We study the largespin regime, and find a great simplicity in the merger waveforms, thanks to the extremely circular character of the plunging orbits. We also quantitatively examine the mixing of quasinormal modes during the ringdown, which induces complicated amplitude and frequency modulations in the waveforms. Finally, we explain how the study of small massratio blackhole binaries helps extending effectiveonebody models for comparablemass, spinning blackhole binaries to any mass ratio and spin magnitude.04/2014; 
Dataset: 84 local APF20 617

Dataset: 13119

Dataset: 122
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ABSTRACT: We report results from a search for gravitational waves produced by perturbed intermediate mass black holes (IMBH) in data collected by LIGO and Virgo between 2005 and 2010. The search was sensitive to astrophysical sources that produced damped sinusoid gravitational wave signals, also known as ringdowns, with frequency $50\le f_{0}/\mathrm{Hz} \le 2000$ and decay timescale $0.0001\lesssim \tau/\mathrm{s} \lesssim 0.1$ characteristic of those produced in mergers of IMBH pairs. No significant gravitational wave candidate was detected. We report upper limits on the astrophysical coalescence rates of IMBHs with total binary mass $50 \le M/\mathrm{M}_\odot \le 450$ and component mass ratios of either 1:1 or 4:1. For systems with total mass $100 \le M/\mathrm{M}_\odot \le 150$, we report a 90%confidence upper limit on the rate of binary IMBH mergers with nonspinning and equal mass components of $6.9\times10^{8}\,$Mpc$^{3}$yr$^{1}$. We also report a rate upper limit for ringdown waveforms from perturbed IMBHs, radiating 1% of their mass as gravitational waves in the fundamental, $\ell=m=2$, oscillation mode, that is nearly three orders of magnitude more stringent than previous results.03/2014;  [Show abstract] [Hide abstract]
ABSTRACT: If binaries consisting of two 100 Msun black holes exist they would serve as extraordinarily powerful gravitationalwave sources, detectable to redshifts of z=2 with the advanced LIGO/Virgo groundbased detectors. Large uncertainties about the evolution of massive stars preclude definitive rate predictions for mergers of these massive black holes. We show that rates as high as hundreds of detections per year, or as low as no detections whatsoever, are both possible. It was thought that the only way to produce these massive binaries was via dynamical interactions in dense stellar systems. This view has been challenged by the recent discovery of several stars with mass greater than 150 Msun in the R136 region of the Large Magellanic Cloud. Current models predict that when stars of this mass leave the main sequence, their expansion is insufficient to allow common envelope evolution to efficiently reduce the orbital separation. The resulting blackholeblackhole binary remains too wide to be able to coalesce within a Hubble time. If this assessment is correct, isolated very massive binaries do not evolve to be gravitationalwave sources. However, other formation channels exist. For example, the high multiplicity of massive stars, and their common formation in relatively dense stellar associations, opens up dynamical channels for massive black hole mergers (e.g., via Kozai cycles or repeated binarysingle interactions). We identify key physical factors that shape the population of very massive blackholeblackhole binaries. Advanced gravitationalwave detectors will provide important constraints on the formation and evolution of very massive stars.The Astrophysical Journal 03/2014; 789(2). · 6.73 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: We present an implementation of the $\mathcal{F}$statistic to carry out the first search in data from the Virgo laser interferometric gravitational wave detector for periodic gravitational waves from a priori unknown, isolated rotating neutron stars. We searched a frequency $f_0$ range from 100 Hz to 1 kHz and the frequency dependent spindown $f_1$ range from $1.6\,(f_0/100\,{\rm Hz}) \times 10^{9}\,$ Hz/s to zero. A large part of this frequency  spindown space was unexplored by any of the allsky searches published so far. Our method consisted of a coherent search over twoday periods using the $\mathcal{F}$statistic, followed by a search for coincidences among the candidates from the twoday segments. We have introduced a number of novel techniques and algorithms that allow the use of the Fast Fourier Transform (FFT) algorithm in the coherent part of the search resulting in a fiftyfold speedup in computation of the $\mathcal{F}$statistic with respect to the algorithm used in the other pipelines. No significant gravitational wave signal was found. The sensitivity of the search was estimated by injecting signals into the data. In the most sensitive parts of the detector band more than 90% of signals would have been detected with dimensionless gravitationalwave amplitude greater than $5 \times 10^{24}$.02/2014;  [Show abstract] [Hide abstract]
ABSTRACT: During the LIGO and Virgo joint science runs in 20092010, gravitational wave (GW) data from three interferometer detectors were analyzed within minutes to select GW candidate events and infer their apparent sky positions. Target coordinates were transmitted to several telescopes for followup observations aimed at the detection of an associated optical transient. Images were obtained for eight such GW candidates. We present the methods used to analyze the image data as well as the transient search results. No optical transient was identified with a convincing association with any of these candidates, and none of the GW triggers showed strong evidence for being astrophysical in nature. We compare the sensitivities of these observations to several model light curves from possible sources of interest, and discuss prospects for future joint GWoptical observations of this type.The Astrophysical Journal Supplement Series 02/2014; 211(1):25. · 16.24 Impact Factor  [Show abstract] [Hide abstract]
ABSTRACT: The Numerical INJection Analysis (NINJA) project is a collaborative effort between members of the numerical relativity and gravitationalwave astrophysics communities. The purpose of NINJA is to study the ability to detect gravitational waves emitted from merging binary black holes and recover their parameters with nextgeneration gravitationalwave observatories. We report here on the results of the second NINJA project, NINJA2, which employs 60 complete binary black hole hybrid waveforms consisting of a numerical portion modelling the late inspiral, merger, and ringdown stitched to a postNewtonian portion modelling the early inspiral. In a "blind injection challenge" similar to that conducted in recent LIGO and Virgo science runs, we added 7 hybrid waveforms to two months of data recolored to predictions of Advanced LIGO and Advanced Virgo sensitivity curves during their first observing runs. The resulting data was analyzed by gravitationalwave detection algorithms and 6 of the waveforms were recovered with false alarm rates smaller than 1 in a thousand years. Parameter estimation algorithms were run on each of these waveforms to explore the ability to constrain the masses, component angular momenta and sky position of these waveforms. We also perform a largescale montecarlo study to assess the ability to recover each of the 60 hybrid waveforms with early Advanced LIGO and Advanced Virgo sensitivity curves. Our results predict that early Advanced LIGO and Advanced Virgo will have a volumeweighted average sensitive distance of 300Mpc (1Gpc) for $10M_{\odot}+10M_{\odot}$ ($50M_{\odot}+50M_{\odot}$) binary black hole coalescences. We demonstrate that neglecting the component angular momenta in the waveform models used in matchedfiltering will result in a reduction in sensitivity for systems with large component angular momenta. [Abstract abridged for ArXiv, full version in PDF]01/2014;  [Show abstract] [Hide abstract]
ABSTRACT: In this study, we perform a Bayesian analysis of massive binary black hole systems using effectiveonebody waveforms. Our waveform model includes merger and quasinormal modes that are tuned to numerical relativity results for many spherical modes of radiation. The additional modes help determine the parameters of progenitor binaries even when their inspiral phase might not be in the sensitivity band of a detector. We show the importance of including subdominant spherical modes beyond the dominant (2,2) mode. We investigate the dependence of detection, measurement uncertainty, and measurement biases from both not including higher order modes and as a function of source parameters. Spin effects will be considered for the first time in this framework with use of the alignedspin effectiveonebody waveform for parameter estimation. We also consider the astrophysical rates for heavy black hole binaries and the chances of detecting them with the advanced detector network.01/2014;  [Show abstract] [Hide abstract]
ABSTRACT: Gravitational waves emitted by blackhole binary systems have the highest signaltonoise ratio in LIGO and Virgo detectors when blackhole spins are aligned with the orbital angular momentum and extremal. For such systems, we extend the effectiveonebody inspiralmergerringdown waveforms to generic mass ratios and spins calibrating them to 38 numericalrelativity nonprecessing waveforms produced by the SXS Collaboration. The numericalrelativity simulations span mass ratios from 1 to 8, spin magnitudes up to 98% of extremality, and last for 40 to 60 gravitationalwave cycles. When the total mass of the binary is between 20Msun and 200Msun, the effectiveonebody nonprecessing (dominant mode) waveforms have overlaps above 99% (using the advancedLIGO design noise spectral density) with all of the 38 nonprecessing numerical waveforms, when maximizing only on initial phase and time. This implies a negligible loss in event rate due to modeling. Moreover, without further calibration, we show that the precessing effectiveonebody (dominant mode) waveforms have overlaps above 97% with two very long, strongly precessing numericalrelativity waveforms, when maximizing only on the initial phase and time.11/2013; 89(6).  [Show abstract] [Hide abstract]
ABSTRACT: The detection of gravitational waves and the extraction of physical information from them requires the prediction of accurate waveforms to be used in template banks. For that purpose, the accuracy of effectiveonebody (EOB) waveforms has been improved over the last years by calibrating them to numericalrelativity (NR) waveforms. So far, the calibration has employed a handful of NR waveforms with a total length of ~30 cycles, the length being limited by the computational cost of NR simulations. Here we address the outstanding problem of the stability of the EOB calibration with respect to the length of NR waveforms. Performing calibration studies against NR waveforms of nonspinning blackhole binaries with mass ratios 1, 1.5, 5, and 8, and with a total length of ~60 cycles, we find that EOB waveforms calibrated against either 30 or 60 cycles will be indistinguishable by the advanced detectors LIGO and Virgo when the signaltonoise ratio (SNR) is below 110. When extrapolating to a very large number of cycles, using very conservative assumptions, we can conclude that stateoftheart nonspinning EOB waveforms of any length are sufficiently accurate for parameter estimation with advanced detectors when the SNR is below 20, the mass ratio is below 5 and total mass is above 20 Msun. The results are not conclusive for the entire parameter space because of current NR errors.11/2013; 89(6).
Publication Stats
4k  Citations  
676.04  Total Impact Points  
Top Journals
Institutions

2014

University of Texas at Brownsville and Texas Southmost College
Brownsville, Texas, United States


2013

Canadian Institute For Advanced Research
Toronto, Ontario, Canada


2011–2013

The Space Science Institute
Boulder, Colorado, United States


2000–2013

California Institute of Technology
 • Jet Propulsion Laboratory
 • Division of Physics, Mathematics, and Astronomy
Pasadena, California, United States


1970–2013

University of Maryland, College Park
 Department of Physics
Maryland, United States


2011–2012

Harvard University
Cambridge, Massachusetts, United States


2006–2011

Loyola University Maryland
 Department of Physics
Baltimore, Maryland, United States


2010

Princeton University
 Department of Physics
Princeton, NJ, United States


2009

Stanford University
Palo Alto, California, United States


2008

French National Centre for Scientific Research
 Institut d'astrophysique spatiale (IAS)
Paris, IledeFrance, France 
Pierre and Marie Curie University  Paris 6
Lutetia Parisorum, ÎledeFrance, France


2003–2004

Institut d'astrophysique de Paris
Lutetia Parisorum, ÎledeFrance, France


1998

Institut des Hautes Études Scientifiques
BuresOrsay, ÎledeFrance, France


1997–1998

CERN
Genève, Geneva, Switzerland


1995–1997

Università di Pisa
Pisa, Tuscany, Italy


1995–1996

INFN  Istituto Nazionale di Fisica Nucleare
Frascati, Latium, Italy
