[gr-qc/0701167] Searching for Massive Black Hole Binaries in the first Mock LISA Data Challenge

Authors: Neil J. Cornish, Edward K. Porter

Date: Tue, 30 Jan 2007

Abstract: The Mock LISA Data Challenge is a worldwide effort to solve the LISA data analysis problem. We present here our results for the Massive Black Hole Binary (BBH) section of Round 1. Our results cover Challenge 1.2.1, where the coalescence of the binary is seen, and Challenge 1.2.2, where the coalescence occurs after the simulated observational period. The data stream is composed of Gaussian instrumental noise plus an unknown BBH waveform. Our search algorithm is based on a variant of the Markov Chain Monte Carlo method that uses Metropolis-Hastings sampling and thermostated frequency annealing. We present results from the training data sets and the blind data sets. We demonstrate that our algorithm is able to rapidly locate the sources, accurately recover the source parameters, and provide error estimates for the recovered parameters.

abs pdf

Jan 31, 2007

0701167 (/preprints/gr-qc)
2007-01-31, 14:56 [edit]


[gr-qc/0701164] Merger Recoils and Spin Flips From Generic Black-Hole Binaries

Authors: Manuela Campanelli, Carlos O. Lousto, Yosef Zlochower, David Merritt

Date: Mon, 29 Jan 2007

Abstract: We report the first results from evolutions of a generic black-hole binary, i.e. a binary containing unequal mass black holes with misaligned spins. Our configuration, which has a mass ratio of 2:1, consists of an initially non-spinning hole orbiting a larger, rapidly spinning hole (specific spin a/m = 0.885), with the spin direction oriented -45-degrees with respect to the orbital plane. We track the inspiral and merger for ~2 orbits and find that the remnant receives a substantial kick of 454 km/s, more than twice as large as the maximum kick from non-spinning binaries. Such a large recoil velocity reopens the possibility that a merged binary can be ejected even from the nucleus of a massive host galaxy. The remnant spin direction is flipped by 103-degrees with respect to the initial spin direction of the larger hole.

abs pdf

Jan 29, 2007

0701164 (/preprints/gr-qc)
2007-01-29, 17:54 [edit]


[gr-qc/0701163] Getting a kick from equal-mass binary black hole mergers

Authors: Michael Koppitz, Denis Pollney, Christian Reisswig, Luciano Rezzolla, Jonathan Thornburg, Peter Diener, Erik Schnetter

Date: Mon, 29 Jan 2007

Abstract: The final evolution of a generic binary black-hole system is expected to give rise to a net recoil velocity as a result of the asymmetry in the beamed gravitational radiation emitted. A quantitative measurement of this effect in the case of binaries with unequal masses has been recently computed by a number of different groups in full numerical-relativity simulations. These have pointed out that kick velocities as large as 175 km/s can be reached for a mass ratio $q\equiv M_1/M_2\simeq 0.36$, where $M_1$ and $M_2$ are the masses of the two black holes. However, a recoil velocity can also be obtained for equal-mass binaries with spinning black holes that have unequal spins. We report here on numerical evolutions of such binary black-hole systems and show, using two independent methods, that even larger kick velocities are possible, with a maximum of $257 \pm 15$ km/s for a system having a spin ratio $a_1/a_2 = -1$ and $a_2\equiv S_2/mˆ2_2=0.584$. This extrapolates to $\sim 450$ km/s for extremal black holes. Such large velocities are not unexpected and we show that the numerical results reproduce, at least qualitatively, the post-Newtonian predictions.

abs pdf

Jan 29, 2007

0701163 (/preprints/gr-qc)
2007-01-29, 17:53 [edit]


[gr-qc/0701154] Where are all the gravastars? Limits upon the gravastar model from accreting black holes

Authors: Avery E. Broderick (1), Ramesh Narayan (1) ((1) Harvard-Smithsonian Center for Astrophysics)

Date: Mon, 29 Jan 2007

Abstract: The gravastar model, which postulates a strongly correlated thin shell of anisotropic matter surrounding a region of anti-de Sitter space, has been proposed as an alternative to black holes. We discuss constraints that present-day observations of well-known black hole candidates place on this model. We focus upon two black hole candidates known to have extraordinarily low luminosities: the supermassive black hole in the Galactic Center, Sagittarius A*, and the stellar-mass black hole, XTE J1118+480. We find that the length scale for modifications of the type discussed in Chapline et al. (2003) must be sub-Planckian.

abs pdf

Jan 29, 2007

0701154 (/preprints/gr-qc)
2007-01-29, 17:53 [edit]


[gr-qc/0701148] Application of the Hilbert-Huang Transform to the Search for Gravitational Waves

Authors: Jordan B. Camp, John K. Cannizzo, Kenji Numata

Date: Sat, 27 Jan 2007

Abstract: We present the application of a novel method of time-series analysis, the Hilbert-Huang Transform, to the search for gravitational waves. This algorithm is adaptive and does not impose a basis set on the data, and thus the time-frequency decomposition it provides is not limited by time-frequency uncertainty spreading. Because of its high time-frequency resolution it has important applications to both signal detection and instrumental characterization. Applications to the data analysis of the ground and space based gravitational wave detectors, LIGO and LISA, are described.

abs pdf

Jan 29, 2007

0701148 (/preprints/gr-qc)
2007-01-29, 17:52 [edit]


[gr-qc/0701145] The Final Fate of Binary Neutron Stars: What Happens After the Merger?

Authors: Matthew D. Duez, Yuk Tung Liu, Stuart L. Shapiro, Masaru Shibata, Branson C. Stephens

Date: Fri, 26 Jan 2007

Abstract: The merger of two neutron stars usually produces a remnant with a mass significantly above the single (nonrotating) neutron star maximum mass. In some cases, the remnant will be stabilized against collapse by rapid, differential rotation. MHD-driven angular momentum transport eventually leads to the collapse of the remnant's core, resulting in a black hole surrounded by a massive accretion torus. Here we present simulations of this process. The plausibility of generating short duration gamma ray bursts through this scenario is discussed.

abs pdf

Jan 29, 2007

0701145 (/preprints/gr-qc)
2007-01-29, 17:52 [edit]


[hep-th/0701238] Introducing Cadabra: a symbolic computer algebra system for field theory problems

Authors: Kasper Peeters

Date: Thu, 25 Jan 2007

Abstract: Cadabra is a new computer algebra system designed specifically for the solution of problems encountered in field theory. It has extensive functionality for tensor polynomial simplification taking care of Bianchi and Schouten identities, for fermions and anti-commuting variables, Clifford algebras and Fierz transformations, implicit coordinate dependence, multiple index types and many other field theory related concepts. The input format is a subset of TeX and thus easy to learn. Both a command-line and a graphical interface are available. The present paper is an introduction to the program using several concrete problems from gravity, supergravity and quantum field theory.

abs pdf

Jan 28, 2007

0701238 (/preprints/hep-th)
2007-01-28, 23:00 [edit]


[gr-qc/0701143] Gravitational recoil from spinning binary black hole mergers

Authors: Frank Herrmann, Ian Hinder, Deirdre Shoemaker, Pablo Laguna, Richard A. Matzner

Date: Sun, 28 Jan 2007

Abstract: The inspiral and merger of binary black holes will likely involve black holes with both unequal masses and arbitrary spins. The gravitational radiation emitted by these binaries will carry angular as well as linear momentum. A net flux of emitted linear momentum implies that the black hole produced by the merger will experience a recoil or kick. Previous studies have focused on the recoil velocity from unequal mass, non-spinning binaries. We present results from simulations of equal mass but spinning black hole binaries and show how a significant gravitational recoil can also be obtained in these situations. We consider the case of black holes with opposite spins of magnitude $a$ aligned/anti-aligned with the orbital angular momentum, with $a$ the dimensionless spin parameters of the individual holes. For the initial setups under consideration, we find a recoil velocity of $V = 475 \KMS a$. Supermassive black hole mergers producing kicks of this magnitude could result in the ejection from the cores of dwarf galaxies of the final hole produced by the collision.

abs pdf

Jan 28, 2007

0701143 (/preprints/gr-qc)
2007-01-28, 23:00 [edit]


[gr-qc/0701139] Report on the first round of the Mock LISA Data Challenges

Authors: K.A. Arnaud, G. Auger, S. Babak, J. Baker, M.J. Benacquista, E. Bloomer, D. Brown, J.B. Camp, J.K. Cannizzo, N. Christensen, J. Clark, N.J. Cornsih, J. Crowder, C. Cutler, S. Fairhurst, L.S. Finn, H. Halloin, K. Hayama, M. Hendry, O. Jeannin, A. Krolak, S.L. Larson, I. Mandel, C. Messenger, R. Meyer, S. Mohanty, R. Nayak, K. Numata, A. Petiteau, M. Pitkin, E. Plagnol, E.K. Porter, R. Prix, C. Roever, B.S. Sathyaprakash, A. Stroeer, P. Sutton, R. Thirumalainambi, D.E. Thompson, J. Toher, R. Umstaetter, M. Vallisneri, A. Vecchio, J-Y. Vinet, J.T. Whelan, G. Woan, (Mock LISA Data Challenge Team)

Date: Thu, 25 Jan 2007

Abstract: The Mock LISA Data Challenges (MLDCs) have the dual purpose of fostering the development of LISA data analysis tools and capabilities, and demonstrating the technical readiness already achieved by the gravitational-wave community in distilling a rich science payoff from the LISA data output. The first round of MLDCs has just been completed: nine data sets containing simulated gravitational wave signals produced either by galactic binaries or massive black hole binaries embedded in simulated LISA instrumental noise were released in June 2006 with deadline for submission of results at the beginning of December 2006. Ten groups have participated in this first round of challenges. Here we describe the challenges, summarise the results, and provide a first critical assessment of the entries.

abs pdf

Jan 26, 2007

0701139 (/preprints/gr-qc)
2007-01-26, 21:14 [edit]


[gr-qc/0701123] Binary black holes on a budget: Simulations using workstations

Authors: Pedro Marronetti, Wolfgang Tichy, Bernd Bruegmann, Jose Gonzalez, Mark Hannam, Sascha Husa, Ulrich Sperhake

Date: Mon, 22 Jan 2007

Abstract: Binary black hole simulations have traditionally been computationally very expensive: current simulations are performed in supercomputers involving dozens if not hundreds of processors, thus systematic studies of the parameter space of binary black hole encounters still seem prohibitive with current technology. Here we present results obtained using dual processor workstations with comparable quality to those obtained using much larger computer resources. For this, we use the multi-layered refinement level code BAM, based on the moving punctures method. BAM provides grid structures composed of boxes of increasing resolution near the center of the grid. In the case of binaries, the highest resolution boxes are placed around each black hole and they track them in their orbits until the final merger when a single set of levels surrounds the black hole remnant. This is particular useful when simulating spinning black holes since the gravitational fields gradients are larger. We present simulations of binaries with equal mass black holes with spins parallel to the binary axis and intrinsic magnitude of S/mˆ2= 0.75. Our results compare favorably to those of previous simulations of this particular system. We show that the moving punctures method produces stable simulations at maximum spatial resolutions up to M/160 and for durations of up to the equivalent of 20 orbital periods.

abs pdf

Jan 22, 2007

0701123 (/preprints/gr-qc)
2007-01-22, 20:20 [edit]


[gr-qc/0701110] Quasiequilibrium black hole-neutron star binaries in general relativity

Authors: Keisuke Taniguchi, Thomas W. Baumgarte, Joshua A. Faber, Stuart L. Shapiro

Date: Fri, 19 Jan 2007

Abstract: We construct quasiequilibrium sequences of black hole-neutron star binaries in general relativity. We solve Einstein's constraint equations in the conformal thin-sandwich formalism, subject to black hole boundary conditions imposed on the surface of an excised sphere, together with the relativistic equations of hydrostatic equilibrium. In contrast to our previous calculations we adopt a flat spatial background geometry and do not assume extreme mass ratios. We adopt a Gamma=2 polytropic equation of state and focus on irrotational neutron star configurations as well as approximately nonspinning black holes. We present numerical results for ratios of the black hole's irreducible mass to the neutron star's ADM mass in isolation of M_{irr}ˆ{BH}/M_{ADM,0}ˆ{NS} = 1, 2, 3, 5, and 10. We consider neutron stars of baryon rest mass M_Bˆ{NS}/M_Bˆ{max} = 83% and 56%, where M_Bˆ{max} is the maximum allowed rest mass of a spherical star in isolation for our equation of state. For these sequences, we locate the onset of tidal disruption and, in cases with sufficiently large mass ratios and neutron star compactions, the innermost stable circular orbit. We compare with previous results for black hole-neutron star binaries and find excellent agreement with third-order post-Newtonian results, especially for large binary separations. We also use our results to estimate the energy spectrum of the outgoing gravitational radiation emitted during the inspiral phase for these binaries.

abs pdf

Jan 22, 2007

0701110 (/preprints/gr-qc)
2007-01-22, 19:52 [edit]


[hep-ph/0701129] Les Houches Lectures on Effective Field Theories and Gravitational Radiation

Authors: Walter D. Goldberger

Date: Tue, 16 Jan 2007

Abstract: These lectures give an overview of the uses of effective field theories in describing gravitational radiation sources for LIGO or LISA. The first lecture reviews some of the standard ideas of effective field theory (decoupling, matching, power counting) mostly in the context of a simple toy model. The second lecture sets up the problem of calculating gravitational wave emission from non-relativistic binary stars by constructing a tower of effective theories that separately describe each scale in the problem: the internal size of each binary constituent, the orbital separation, and the wavelength of radiated gravitons.

abs pdf

Jan 22, 2007

0701129 (/preprints/hep-ph)
2007-01-22, 19:47 [edit]


[gr-qc/0701109] WhiskyMHD: a new numerical code for general relativistic magnetohydrodynamics

Authors: B. Giacomazzo (1,2), L. Rezzolla (1,3) ((1) Albert Einstein Institute, Golm, Germany, (2) SISSA and INFN, Trieste, Italy, (3) Department of Physics, Louisiana State University, USA)

Date: Fri, 19 Jan 2007

Abstract: The accurate modelling of astrophysical scenarios involving compact objects and magnetic fields, such as the collapse of rotating magnetized stars to black holes or the phenomenology of gamma-ray bursts, requires the solution of the Einstein equations together with those of general-relativistic magnetohydrodynamics. We present a new numerical code developed to solve the full set of general-relativistic magnetohydrodynamics equations in a dynamical and arbitrary spacetime with high-resolution shock-capturing techniques on domains with adaptive mesh refinements. After a discussion of the equations solved and of the techniques employed, we present a series of testbeds carried out to validate the code and assess its accuracy. Such tests range from the solution of relativistic Riemann problems in flat spacetime, over to the stationary accretion onto a Schwarzschild black hole and up to the evolution of oscillating magnetized stars in equilibrium and constructed as consistent solutions of the coupled Einstein-Maxwell equations.

abs pdf

Jan 22, 2007

0701109 (/preprints/gr-qc)
2007-01-22, 10:25 [edit]


[gr-qc/0701086] Mining information from binary black hole mergers: a comparison of estimation methods for complex exponentials in noise

Authors: Emanuele Berti, Vitor Cardoso, Jose A. Gonzalez, Ulrich Sperhake

Date: Tue, 16 Jan 2007

Abstract: The ringdown phase following a binary black hole merger is usually assumed to be well described by a linear superposition of complex exponentials (quasinormal modes). In the strong-field conditions typical of a binary black hole merger, non-linear effects may produce mode coupling. Mode coupling can also be induced by the black hole's rotation, or by expanding the radiation field in terms of spin-weighted spherical harmonics (rather than spin-weighted spheroidal harmonics). Observing deviations from the predictions of linear black hole perturbation theory requires optimal fitting techniques to extract ringdown parameters from numerical waveforms, which are inevitably affected by numerical error. So far, non-linear least-squares fitting methods have been used as the standard workhorse to extract frequencies from ringdown waveforms. These methods are known not to be optimal for estimating parameters of complex exponentials. Furthermore, different fitting methods have different performance in the presence of noise. The main purpose of this paper is to introduce the gravitational wave community to modern variations of a linear parameter estimation technique first introduced in 1795 by Prony: the Kumaresan-Tufts and matrix pencil methods. Using ‘test’ damped sinusoidal signals in Gaussian white noise we illustrate the advantages of these methods, showing that they have variance and bias at least comparable to standard non-linear least-squares techniques. Then we compare the performance of different methods on unequal-mass binary black hole merger waveforms. The methods we discuss should be useful both theoretically (to monitor errors and search for non-linearities in numerical relativity simulations) and experimentally (for parameter estimation from ringdown signals after a gravitational wave detection).

abs pdf

Jan 16, 2007

0701086 (/preprints/gr-qc)
2007-01-16, 18:05 [edit]


[gr-qc/0412010] The final phase of inspiral of neutron stars: realistic equations of state

Authors: Dorota Gondek-Rosinska (LUTH, CAMK), Michal Bejger (CAMK), Tomek Bulik (CAMK), Eric Gourgoulhon (LUTH), Pawel Haensel (LUTH, CAMK), Francois Limousin (LUTH), Keisuke Taniguchi, Leszek Zdunik (CAMK)

Date: Wed, 10 Jan 2007

Abstract: Coalescing compact star binaries are expected to be among the strongest sources of gravitational radiation to be seen by laser interferometers. We present calculations of the final phase of inspiral of equal mass irrotational neutron star binaries and strange quark star binaries. Six types of equations of state at zero temperature are used - three realistic nuclear equations of state of various softness and three different MIT bag models of strange quark matter. We study the precoalescing stage within the Isenberg-Wilson-Mathews approximation of general relativity using a multidomain spectral method. The gravitational-radiation driven evolution of the binary system is approximated by a sequence of quasi-equilibrium configurations at fixed baryon number and decreasing separation. We find that the innermost stable circular orbit (ISCO) is given by an orbital instability for binary strange quark stars and by the mass-shedding limit for neutron star binaries. The gravitational wave frequency at the ISCO, which marks the end of the inspiral phase, is found to be around 1100-1460 Hz for two 1.35 solar masses irrotational strange stars described by the MIT bag model and between 800 Hz and 1230 Hz for neutron stars.

abs pdf

Jan 11, 2007

0412010 (/preprints/gr-qc)
2007-01-11, 10:03 [edit]


[math-ph/0701015] Using Spectral Method as an Approximation for Solving Hyperbolic PDEs

Authors: P. Pedram, M. Mirzaei, S. S. Gousheh

Date: Sat, 6 Jan 2007

Abstract: We demonstrate an application of the spectral method as a numerical approximation for solving Hyperbolic PDEs. In this method a finite basis is used for approximating the solutions. In particular, we demonstrate a set of such solutions for cases which would be otherwise almost impossible to solve by the more routine methods such as the Finite Difference Method. Eigenvalue problems are included in the class of PDEs that are solvable by this method. Although any complete orthonormal basis can be used, we discuss two particularly interesting bases: the Fourier basis and the quantum oscillator eigenfunction basis. We compare and discuss the relative advantages of each of these two bases.

abs pdf

Jan 11, 2007

0701015 (/preprints/math-ph)
2007-01-11, 10:03 [edit]


[astro-ph/0701228] Experimental Evidence of Black Holes

Authors: Andreas Mueller

Date: Tue, 9 Jan 2007 10:14:51 GMT (2078

Abstract: Classical black holes are solutions of the field equations of General Relativity. Many astronomical observations suggest that black holes really exist in nature. However, an unambiguous proof for their existence is still lacking. Neither event horizon nor intrinsic curvature singularity have been observed by means of astronomical techniques. This paper introduces to particular features of black holes. Then, we give a synopsis on current astronomical techniques to detect black holes. Further methods are outlined that will become important in the near future. For the first time, the zoo of black hole detection techniques is completely presented and classified into kinematical, spectro-relativistic, accretive, eruptive, obscurative, aberrative, temporal, and gravitational-wave induced verification methods. Principal and technical obstacles avoid undoubtfully proving black hole existence. We critically discuss alternatives to the black hole. However, classical rotating Kerr black holes are still the best theoretical model to explain astronomical observations.

abs pdf

Jan 11, 2007

0701228 (/preprints/astro-ph)
2007-01-11, 10:02 [edit]


[gr-qc/0701047] Post-Newtonian gravitational radiation and equations of motion via direct integration of the relaxed Einstein equations. IV. Radiation reaction for binary systems with spin-spin coupling

Authors: Han Wang, Clifford M. Will (Washington University)

Date: Mon, 8 Jan 2007

Abstract: Using post-Newtonian equations of motion for fluid bodies that include radiation-reaction terms at 2.5 and 3.5 post-Newtonian (PN) order O[(v/c)ˆ5] and O[(v/c)ˆ7] beyond Newtonian order), we derive the equations of motion for binary systems with spinning bodies, including spin-spin effects. In particular we determine the effects of radiation-reaction coupled to spin-spin effects on the two-body equations of motion, and on the evolution of the spins. We find that radiation damping causes a 3.5PN order, spin-spin induced precession of the individual spins. This contrasts with the case of spin-orbit coupling, where there is no effect on the spins at 3.5PN order. Employing the equations of motion and of spin precession, we verify that the loss of total energy and total angular momentum induced by spin-spin effects precisely balances the radiative flux of those quantities calculated by Kidder et al.

abs pdf

Jan 08, 2007

0701047 (/preprints/gr-qc)
2007-01-08, 22:58 [edit]


[gr-qc/0701042] High-precision measurement of frame-dragging with the Mars Global Surveyor spacecraft in the gravitational field of Mars

Authors: Lorenzo Iorio

Date: Sat, 6 Jan 2007

Abstract: In this letter we accurately measure the general relativistic gravitomagnetic Lense-Thirring effect by analyzing the post-fit residuals of the out-of-plane portion of the orbit of the Martian polar orbiter Mars Global Surveyor (MGS) over a time span of about 5 years (14 November 1999-14 January 2005). Our result is \mu= 0.9937 +/- 0.0053; general relativity predicts \mu=1. A previous test of the Lense-Thirring effect conducted in the Earth's gravitational field with the LAGEOS satellites reached an about 10% level, although it is still controversial. The expected accuracy of the GP-B mission, aimed at the detection of another gravitomagnetic effect in the terrestrial gravitational field, i.e. the Schiff precession of a gyroscope, is about 1%. The precision of our test is 0.5$%.

abs pdf

Jan 08, 2007

0701042 (/preprints/gr-qc)
2007-01-08, 22:56 [edit]


[astro-ph/0701059] The Evolution of Compact Binary Star Systems

Authors: Konstantin Postnov (SAI), Lev Yungelson (Institute of Astronomy RAS)

Date: Wed, 3 Jan 2007

Abstract: We review the formation and evolution of compact binary stars consisting of white dwarfs (WDs), neutron stars (NSs), and black holes (BHs). Binary NSs and BHs are thought to be the primary astrophysical sources of gravitational waves (GWs) within the frequency band of ground-based detectors, while compact binaries of WDs are important sources of GWs at lower frequencies to be covered by space interferometers (LISA). Major uncertainties in the current understanding of properties of NSs and BHs most relevant to the GW studies are discussed, including the treatment of the natal kicks which compact stellar remnants acquire during the core collapse of massive stars and the common envelope phase of binary evolution. We discuss the coalescence rates of binary NSs and BHs and prospects for their detections, the formation and evolution of binary WDs and their observational manifestations. Special attention is given to AM CVn-stars -- compact binaries in which the Roche lobe is filled by another WD or a low-mass partially degenerate helium-star, as these stars are thought to be the best LISA verification binary GW sources.

abs pdf

Jan 07, 2007

0701059 (/preprints/astro-ph)
2007-01-07, 18:34 [edit]


[gr-qc/0701038] Are moving punctures equivalent to moving black holes?

Authors: Jonathan Thornburg, Peter Diener, Denis Pollney, Luciano Rezzolla, Erik Schnetter, Ed Seidel, Ryoji Takahashi

Date: Fri, 5 Jan 2007

Abstract: When simulating the inspiral and coalescence of a binary black-hole system, special care needs to be taken in handling the singularities. Two main techniques are used in numerical-relativity simulations: A first and more traditional one ‘excises’ a spatial neighborhood of the singularity from the numerical grid on each spacelike hypersurface. A second and more recent one, instead, begins with a ‘puncture’ solution and then evolves the full 3-metric, including the singular point. While the first approach is mathematically and numerically well-defined, the second one still maintains a non-differentiable point within the black hole. No strong-field evidence has yet been provided to show that the two approaches are indeed dynamically equivalent. To address this question we have used both techniques to evolve a binary system of equal-mass non-spinning black holes and compared the evolution of two curvature 4-scalars with proper time along the invariantly-defined worldline midway between the two black holes. Using Richardson-extrapolation techniques to reduce the influence of the finite-difference truncation error, we find that the moving-punctures and excision evolutions produce the same spacetimes along that worldline. This represents the first strong-field and dynamical evidence that the moving-puncture prescription is robust both mathematically and numerically.

abs pdf

Jan 07, 2007

0701038 (/preprints/gr-qc)
2007-01-07, 18:34 [edit]


[astro-ph/0701004] Stochastic background from inspiralling double neutron stars

Authors: Tania Regimbau

Date: Sat, 30 Dec 2006

Abstract: We review the contribution of extra galactic inspiralling double neutron stars, to the LISA astrophysical gravitational wave foreground. Using recent fits of the star formation rate, we show that sources beyond $z_*=0.005$ contribute to a truly continuous background, which may dominate the LISA instrumental noise in the range $3 \simeq 10ˆ{-4}$ - $1 \times 10ˆ{-2}$ Hz and overwhelm the galactic WD-WD confusion noise at frequencies larger than $\nu_o \simeq 2\times 10ˆ{-3}$.

abs pdf

Jan 04, 2007

0701004 (/preprints/astro-ph)
2007-01-04, 12:05 [edit]


[gr-qc/0701026] A comparison of methods for gravitational wave burst searches from LIGO and Virgo

Authors: F. Beauville, M.-A. Bizouard, L. Blackburn, L. Bosi, L. Brocco, D. Brown, D. Buskulic, F. Cavalier, S. Chatterji, N. Christensen, A.-C. Clapson, S. Fairhurst, D. Grosjean, G. Guidi, P. Hello, S. Heng, M. Hewitson, E. Katsavounidis, S. Klimenko, M. Knight, A. Lazzarini, N. Leroy, F. Marion, J. Markowitz, C. Melachrinos, B. Mours, F. Ricci, A. Viceré, I. Yakushin, M. Zanolin

Date: Wed, 3 Jan 2007

Abstract: The search procedure for burst gravitational waves has been studied using 24 hours of simulated data in a network of three interferometers (Hanford 4-km, Livingston 4-km and Virgo 3-km are the example interferometers). Several methods to detect burst events developed in the LIGO Scientific Collaboration (LSC) and Virgo collaboration have been studied and compared. We have performed coincidence analysis of the triggers obtained in the different interferometers with and without simulated signals added to the data. The benefits of having multiple interferometers of similar sensitivity are demonstrated by comparing the detection performance of the joint coincidence analysis with LSC and Virgo only burst searches. Adding Virgo to the LIGO detector network can increase by 50% the detection efficiency for this search. Another advantage of a joint LIGO-Virgo network is the ability to reconstruct the source sky position. The reconstruction accuracy depends on the timing measurement accuracy of the events in each interferometer, and is displayed in this paper with a fixed source position example.

abs pdf

Jan 04, 2007

0701026 (/preprints/gr-qc)
2007-01-04, 12:04 [edit]


[gr-qc/0701027] Detailed comparison of LIGO and Virgo Inspiral Pipelines in Preparation for a Joint Search

Authors: F. Beauville, M.-A. Bizouard, L. Blackburn, L. Bosi, L. Brocco, D. Brown, D. Buskulic, F. Cavalier, S. Chatterji, N. Christensen, A.-C. Clapson, S. Fairhurst, D. Grosjean, G. Guidi, P. Hello, S. Heng, M. Hewitson, E. Katsavounidis, S. Klimenko, M. Knight, A. Lazzarini, N. Leroy, F. Marion, J. Markowitz, C. Melachrinos, B. Mours, F. Ricci, A. Viceré, I. Yakushin, M. Zanolin

Date: Wed, 3 Jan 2007

Abstract: Presented in this paper is a detailed and direct comparison of the LIGO and Virgo binary neutron star detection pipelines. In order to test the search programs, numerous inspiral signals were added to 24 hours of simulated detector data. The efficiencies of the different pipelines were tested, and found to be comparable. Parameter estimation routines were also tested. We demonstrate that there are definite benefits to be had if LIGO and Virgo conduct a joint coincident analysis; these advantages include increased detection efficiency and the providing of source sky location information.

abs pdf

Jan 04, 2007

0701027 (/preprints/gr-qc)
2007-01-04, 12:04 [edit]


[gr-qc/0701016] Comparisons of binary black hole merger waveforms

Authors: John G. Baker, Manuela Campanelli, Frans Pretorius, Yosef Zlochower

Date: Mon, 1 Jan 2007

Abstract: This a particularly exciting time for gravitational wave physics. Ground-based gravitational wave detectors are now operating at a sensitivity such that gravitational radiation may soon be directly detected, and recently several groups have independently made significant breakthroughs that have finally enabled numerical relativists to solve the Einstein field equations for coalescing black-hole binaries, a key source of gravitational radiation. The numerical relativity community is now in the position to begin providing simulated merger waveforms for use by the data analysis community, and it is therefore very important that we provide ways to validate the results produced by various numerical approaches. Here, we present a simple comparison of the waveforms produced by two very different, but equally successful approaches--the generalized harmonic gauge and the moving puncture methods. We compare waveforms of equal-mass black hole mergers with minimal or vanishing spins. The results show exceptional agreement for the final burst of radiation, with some differences attributable to small spins on the black holes in one case.

abs pdf

Jan 03, 2007

0701016 (/preprints/gr-qc)
2007-01-03, 08:21 [edit]


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