Michele's wiki/blog

Authors: Neil J. Cornish, Joey Shapiro Key

Date: 29 Apr 2010

Abstract: Several scenarios have been proposed in which the orbits of binary black holes enter the band of a gravitational wave detector with significant eccentricity. To avoid missing these signals or biasing the parameter estimation it is important that we consider waveform models that account for eccentricity. The ingredients needed to compute post-Newtonian (PN) waveforms produced by spinning black holes inspiralling on quasi-eccentric orbits have been available for almost two decades at 2 PN order, and this work has recently been extended to 2.5 PN order. However, the computational cost of directly implementing these waveforms is high, requiring many steps per orbit to evolve the system of coupled differential equations. Here we employ a separation of timescales and a generalized Keplarian parameterization of the orbits to produce efficient waveforms describing spinning black hole binaries with arbitrary spin orientations on quasi-eccentric orbits to 1.5 PN order. Our solution includes the spin contributions to the decay of the semi-major axis and eccentricity. We outline a scheme for extending our approach to higher post-Newtonian order.

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Authors: Xin Wu (Nanchang University), Yi Xie (Nanjing University)

Date: 28 Apr 2010

Abstract: Full general relativity requires that chaos indicators should be invariant in various spacetime coordinate systems for a given relativistic dynamical problem. On the basis of this point, we calculate the invariant Lyapunov exponents (LEs) for one of the spinning compact binaries in the conservative second post-Newtonian (2PN) Lagrangian formulation without the dissipative effects of gravitational radiation, using the two-nearby-orbits method with projection operations and with coordinate time as an independent variable. It is found that the actual source leading to zero LEs in one paper [J. D. Schnittman and F. A. Rasio, Phys. Rev. Lett. 87, 121101 (2001)] but to positive LEs in the other [N. J. Cornish and J. Levin, Phys. Rev. Lett. 89, 179001 (2002)] does not mainly depend on rescaling, but is due to two slightly different treatments of the LEs. It takes much more CPU time to obtain the stabilizing limit values as reliable values of LEs for the former than to get the slopes (equal to LEs) of the fit lines for the latter. Due to coalescence of some of the black holes, the LEs from the former are not an adaptive indicator of chaos for comparable mass compact binaries. In this case, the invariant fast Lyapunov indicator (FLI) of two-nearby orbits, as a very sensitive tool to distinguish chaos from order, is worth recommending. As a result, we do again find chaos in the 2PN approximation through different ratios of FLIs varying with time. Chaos cannot indeed be ruled out in real binaries.

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Authors: Ulvi Yurtsever, Caren Marzban, Marina Meila

Date: 28 Apr 2010

Abstract: We discuss some mathematical aspects of the problem of inverting gravitational field data to extract the underlying mass distribution. While the forward problem of computing the gravity field from a given mass distribution is mathematically straightforward, the inverse of this forward map has some interesting features that make inversion a difficult problem. In particular, the forward map has an infinite-dimensional kernel which makes the inversion fundamentally non-unique. We characterize completely the kernels of two gravitational forward maps, one mapping mass density to the Newtonian scalar potential, and the other mapping mass density to the gravity gradient tensor, which is the quantity most commonly measured in field observations. In addition, we present some results on unique inversion under constrained conditions, and comment on the roles the kernel of the forward map and non-uniqueness play in discretized approaches to the continuum inverse problem.

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Authors: Christian Reisswig, Sascha Husa, Luciano Rezzolla, Ernst Nils Dorband, Denis Pollney, Jennifer Seiler

Date: 2 Jul 2009

Abstract: Binary black-hole systems with spins aligned or anti-aligned to the orbital angular momentum provide the natural ground to start detailed studies of the influence of strong-field spin effects on gravitational wave observations of coalescing binaries. Furthermore, such systems may be the preferred end-state of the inspiral of generic supermassive binary black-hole systems. In view of this, we have computed the inspiral and merger of a large set of binary systems of equal-mass black holes with spins parallel to the orbital angular momentum but otherwise arbitrary. Our attention is particularly focused on the gravitational-wave emission so as to quantify how much spin effects contribute to the signal-to-noise ratio, to the horizon distances, and to the relative event rates for the representative ranges in masses and detectors. As expected, the signal-to-noise ratio increases with the projection of the total black hole spin in the direction of the orbital momentum. We find that equal-spin binaries with maximum spin aligned with the orbital angular momentum are more than "three times as loud" as the corresponding binaries with anti-aligned spins, thus corresponding to event rates up to 30 times larger. We also consider the waveform mismatch between the different spinning configurations and find that, within our numerical accuracy, binaries with opposite spins S_1=-S_2 cannot be distinguished whereas binaries with spin S_1=S_2 have clearly distinct gravitational-wave emissions. Finally, we derive a simple expression for the energy radiated in gravitational waves and find that the binaries always have efficiencies E_rad/M > 3.6%, which can become as large as E_rad/M = 10% for maximally spinning binaries with spins aligned with the orbital angular momentum.

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Authors: Denis Pollney, Christian Reisswig

Date: 23 Apr 2010

Abstract: In addition to the dominant oscillatory gravitational wave signals produced during binary inspirals, a non-oscillatory component arises from the nonlinear "memory" effect, sourced by the emitted gravitational radiation. The memory grows significantly during the late inspiral and merger, modifying the signal by an almost step-function profile, and making it difficult to model by approximate methods. We use numerical evolutions of binary black holes to evaluate the nonlinear memory during late-inspiral, merger and ringdown. We identify two main components of the signal: the monotonically growing portion corresponding to the memory, and an oscillatory part which sets in roughly at the time of merger and is due to the black hole ringdown. Counter-intuitively, the ringdown is most prominent for models with the lowest total spin. Thus, the case of maximally spinning black holes anti-aligned to the orbital angular momentum exhibits the highest signal-to-noise (SNR) for interferometric detectors. The largest memory offset, however, occurs for highly spinning black holes, with an estimated value of hˆtot_20 \approx 0.24 in the maximally spinning case. These results are central to determining the detectability of nonlinear memory through pulsar timing array measurements.

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Authors: C. Molina, Paolo Pani, Vitor Cardoso, Leonardo Gualtieri

Date: 22 Apr 2010

Abstract: Dynamical Chern-Simons gravity is an extension of General Relativity in which the gravitational field is coupled to a scalar field through a parity-violating Chern-Simons term. In this framework, we study perturbations of spherically symmetric black hole spacetimes, assuming that the background scalar field vanishes. Our results suggest that these spacetimes are stable, and small perturbations die away as a ringdown. However, in contrast to standard General Relativity, the gravitational waveforms are also driven by the scalar field. Thus, the gravitational oscillation modes of black holes carry imprints of the coupling to the scalar field. This is a smoking gun for Chern-Simons theory and could be tested with gravitational-wave detectors, such as LIGO or LISA. For negative values of the coupling constant, ghosts are known to arise, and we explicitly verify their appearance numerically. Our results are validated using both time evolution and frequency domain methods.

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Authors: Diego Chialva

Date: 12 Apr 2010

Abstract: We study the production, spectrum and detectability of gravitational waves in models of the early Universe where first order phase transitions occur during inflation. We consider all possible sources: bubble collisions, dynamics of the fluid, thermal fluctuations, turbulence,

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Authors: Lee Samuel Finn, Andrea N. Lommen

Date: 20 Apr 2010

Abstract: Efforts to detect gravitational waves by timing an array of pulsars have focused traditionally on stationary gravitational waves: e.g., stochastic or periodic signals. Gravitational wave bursts — signals whose duration is much shorter than the observation period — will also arise in the pulsar timing array waveband. Sources that give rise to detectable bursts include the formation or coalescence of supermassive black holes (SMBHs), the periapsis passage of compact objects in highly elliptic or unbound orbits about a SMBH, or cusps on cosmic strings. Here we describe how pulsar timing array data may be analyzed to detect and characterize these bursts. Our analysis addresses, in a mutually consistent manner, a hierarchy of three questions: \emph{i}) What are the odds that a dataset includes the signal from a gravitational wave burst? \emph{ii}) Assuming the presence of a burst, what is the direction to its source? and \emph{iii}) Assuming the burst propagation direction, what is the burst waveform's time dependence in each of its polarization states? Applying our analysis to synthetic data sets we find that we can \emph{detect} gravitational waves even when the radiation is too weak to either localize the source of infer the waveform, and \emph{detect} and \emph{localize} sources even when the radiation amplitude is too weak to permit the waveform to be determined. While the context of our discussion is gravitational wave detection via pulsar timing arrays, the analysis itself is directly applicable to gravitational wave detection using either ground or space-based detector data.

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Authors: M.Cattani

Date: 14 Apr 2010

Abstract: In a recent paper we have deduced the basic equations that predict the emission of gravitational waves (GW) according to the Einstein gravitation theory. In a subsequent paper these equations have been used to calculate the luminosities and the amplitudes of the waves generated by binary stars, pulsations of neutron stars, wobbling of deformed neutron stars, oscillating quadrupoles, rotating bars and collapsing and bouncing cores of supernovas. We show here how the GW could be detected in our laboratories. This paper, like the preceding ones, was written to graduate and postgraduate students of Physics.

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Authors: Nicholas Stone, Abraham Loeb (Harvard)

Date: 27 Apr 2010

Abstract: A precise electromagnetic measurement of the sky coordinates and redshift of a coalescing black hole binary holds the key for using its gravitational wave (GW) signal to constrain cosmological parameters and to test general relativity. Here we show that the merger of ~10ˆ{6-8}M_sun black holes is generically followed over a period of years by multiple electromagnetic flares from tidally disrupted stars. The sudden recoil imparted to the merged black hole by GW emission results promptly in a tidal disruption rate of stars as high as ~0.1-1 per year. The sequential disruption of stars within a single galaxy over a short period provides a unique electromagnetic flag of a recent black hole coalescence event, and can be used on its own to calibrate the expected rate of GW sources for pulsar timing arrays or the proposed Laser Interferometer Space Antenna (LISA).

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Authors: Tobias S. Keidl, Abhay G. Shah, John L. Friedman, Dong-Hoon Kim, Larry R. Price

Date: 13 Apr 2010

Abstract: In this, the first of two companion papers, we present a method for finding the gravitational self-force in a radiation gauge for a particle moving on a geodesic in a Schwarzschild or Kerr spacetime. The method involves a mode-sum renormalization of a spin-weight $\pm 2$ perturbed Weyl scalar and the subsequent reconstruction from a Hertz potential of the renormalized perturbed metric. We show that the Hertz potential is uniquely specified by the requirement that it have no angular harmonics with $\ell\leq 2$. The resulting perturbed metric is singular only at the position of the particle: It is smooth on the axis of symmetry. An extension of an earlier result by Wald is needed to show that the perturbed metric is determined up to a gauge transformation and an infinitesimal change in the black hole mass and spin. We show that the singular behavior of the metric and self-force has the same power-law behavior in $L=\ell+½$ as in a Lorenz gauge (with different coefficients). We compute the singular Weyl scalar and its mode-sum decomposition to subleading order in $L$ for a particle in circular orbit in a Schwarzschild geometry and obtain the renormalized field. Because the singular field can be defined as this mode sum, the coefficients of each angular harmonic in the sum must agree with the large $L$ limit of the corresponding coefficients of the retarded field. One may compute the singular field by matching the retarded field to a power series in $L$ and subtracting off the leading and subleading terms in this series. We do so, and compare the accuracy of the two methods. Details of the numerical computation of the perturbed metric, the self-force, and the quantity $h_{\alpha\beta}uˆ\alpha uˆ\beta$ (gauge invariant under helically symmetric gauge transformations) are presented for this test case in the companion paper.

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Authors: Salvatore Vitale, Michele Zanolin

Date: 26 Apr 2010

Abstract: In this paper we use a new methodology to calculate analytically the error for a maximum likelihood estimate (MLE) of physical parameters from Gravitational Wave (GW) signals, by applying it to IMR waves from non-spinning binary system. While the existing literature focuses on using the Cramer Rao Lower bound. (CRLB) as a mean to approximate the errors for large signal to noise ratios, taking into account only the fist derivative of the signal, we consider also the higher order derivatives, obtaining an improved estimation of parameters' errors. We see how the bias is in general non negligible for high mass systems (200 solar masses and above), due to the nonlinear dipendence of the signal on the parameters, where it can become the most important contributor to the parameters' errors. This new feature will require numerical injections to be proved true.

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Authors: Abdul H. Mroué, Harald P. Pfeiffer, Lawrence E. Kidder, Saul A. Teukolsky

Date: 27 Apr 2010

Abstract: We compare different methods of computing the orbital eccentricity of quasi-circular binary black hole systems using the orbital variables and gravitational wave phase and frequency. For eccentricities of about a per cent, most methods work satisfactorily. For small eccentricity, however, the gravitational wave phase allows a particularly clean and reliable measurement of the eccentricity. Furthermore, we measure the decay of the orbital eccentricity during the inspiral and find reasonable agreement with post-Newtonian results. Finally, we measure the periastron advance of non-spinning binary black holes, and we compare them to post-Newtonian approximations. With the low uncertainty in the measurement of the periastron advance, we positively detect deviations between fully numerical simulations and post-Newtonian calculations.

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Authors: R. O'Shaughnessy (1), V. Kalogera (2), K. Belczynski (3 and 4) ((1) Center for Gravitational Wave Physics, Penn State University, (2) Northwestern University, (3) Los Alamos National Laboratory, (4) Astronomical Observatory, University of Warsaw)

Date: 25 Aug 2009

Abstract: We estimate binary compact object merger detection rates for LIGO, including the binaries formed in ellipticals long ago. Specifically, we convolve hundreds of model realizations of elliptical- and spiral-galaxy population syntheses with a model for elliptical- and spiral-galaxy star formation history as a function of redshift. Our results favor local merger rate densities of 4\times 10ˆ{-3} {Mpc}ˆ{-3}{Myr}ˆ{-1} for binary black holes (BH), 3\times 10ˆ{-2} {Mpc}ˆ{-3}{Myr}ˆ{-1} for binary neutron stars (NS), and 10ˆ{-2} {Mpc}ˆ{-3}{Myr}ˆ{-1} for BH-NS binaries. Mergers in elliptical galaxies are a significant fraction of our total estimate for BH-BH and BH-NS detection rates; NS-NS detection rates are dominated by the contribution from spiral galaxies. Using only models that reproduce current observations of Galactic NS-NS binaries, we find slightly higher rates for NS-NS and largely similar ranges for BH-NS and BH-BH binaries. Assuming a detection signal-to-noise ratio threshold of 8 for a single detector (as part of a network), corresponding to radii \Cv of the effective volume inside of which a single LIGO detector could observe the inspiral of two 1.4 M_\sun neutron stars of 14 Mpc and 197 Mpc, for initial and advanced LIGO, we find event rates of any merger type of 2.9* 10ˆ{-2} -- 0.46 and 25-400 per year (at 90% confidence level), respectively. We also find that the probability P_{detect} of detecting one or more mergers with this single detector can be approximated by (i) P_{detect}\simeq 0.4+0.5\log (T/0.01{yr}), assuming \Cv=197 {Mpc} and it operates for T years, for T between 2 days and 0.1 {yr}); or by (ii) P_{detect}\simeq 0.5 + 1.5 \log \Cv/32{Mpc}, for one year of operation and for $\Cv$ between 20 and 70 Mpc. [ABRIDGED]

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Authors: K. Belczynski, M. Dominik, T. Bulik, R. O'Shaughnessy, C.L. Fryer, D.E. Holz

Date: 2 Apr 2010

Abstract: By combining advances in observational astrophysics with recent progress in stellar evolution, we show that there will be a remarkably high number of black holes with compact object (neutron star or black hole) companions in the local Universe. Data from the Sloan Digital Sky Survey (300,000 galaxies) indicates that recent star formation (within the last 1 billion years) is bimodal: half the stars form from gas with high amounts of metals (solar metallicity), and the other half form with small contribution of elements heavier than Helium (20% solar). Theoretical studies of mass loss derive significantly higher stellar-origin black hole masses (30-80 Msun) than previously estimated for sub-solar compositions. We combine these findings to estimate the probability for detection of gravitational waves arising from the inspiral of double compact objects. Our results show that a low metallicity environment significantly boosts the formation of double compact object binaries with at least one black hole. In particular, we find the gravitational-wave detection rate is increased by a factor of 20 if the metallicity is decreased from solar (as in all previous estimates) to a 50-50 mixture of solar and 10% solar metallicity. The current sensitivity of the largest instruments to double neutron-star binaries (VIRGO: 9 Mpc; LIGO: 18) is not high enough to ensure a first detection. However, our results indicate that if a future instrument increased the reach to 50-100Mpc, a detection of gravitational waves would be expected within the first year of observation. It was previously thought that binary neutron stars were the most likely source, but our results indicate that black-hole binaries are 25-times more likely. We are therefore truly on the cusp of seeing gravitational waves, and the first source ever to be seen is likely to be a black hole binary.

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Authors: Eric Chassande-Mottin, Martin Hendry, Patrick J. Sutton, Szabolcs Márka

Date: 12 Apr 2010

Abstract: Gravitational waves (GWs) are expected to play a crucial r\ˆole in the development of multimessenger astrophysics. The combination of GW observations with other astrophysical triggers, such as from gamma-ray and X-ray satellites, optical/radio telescopes, and neutrino detectors allows us to decipher science that would otherwise be inaccessible. In this paper, we provide a broad review from the multimessenger perspective of the science reach offered by the third generation interferometric GW detectors and by the Einstein Telescope (ET) in particular. We focus on cosmic transients, and base our estimates on the results obtained by ET's predecessors GEO, LIGO, and Virgo.

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Authors: Jonathan R. Gair, Christopher Tang, Marta Volonteri

Date: 12 Apr 2010

Abstract: One of the sources of gravitational waves for the proposed space-based gravitational wave detector, the Laser Interferometer Space Antenna (LISA), are the inspirals of compact objects into supermassive black holes in the centres of galaxies - extreme-mass-ratio inspirals (EMRIs). Using LISA observations, we will be able to measure the parameters of each EMRI system detected to very high precision. However, the statistics of the set of EMRI events observed by LISA will be more important in constraining astrophysical models than extremely precise measurements for individual systems. The black holes to which LISA is most sensitive are in a mass range that is difficult to probe using other techniques, so LISA provides an almost unique window onto these objects. In this paper we explore, using Bayesian techniques, the constraints that LISA EMRI observations can place on the mass function of black holes at low redshift. We describe a general framework for approaching inference of this type — using multiple observations in combination to constrain a parameterised source population. Assuming that the scaling of EMRI rate with black hole mass is known and taking a black hole distribution given by a simple power law, dn/d(ln M) = A (M/M_*)ˆb, we find that LISA could measure the parameters to a precision of D(ln A) ~ 0.08, and D(b) ~ 0.03 for a reference model that predicts ~1000 events. Even with as few as 10 events, LISA should constrain the slope to a precision ~0.3, which is the current level of observational uncertainty in the low-mass slope of the black hole mass function. We also consider a model in which A and b evolve with redshift, but find that EMRI observations alone do not have much power to probe such an evolution.

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Authors: David Garofalo, David L. Meier

Date: 9 Apr 2010

Abstract: The fundamental role played by black holes in our study of microquasars, gamma ray bursts, and the outflows from active galactic nuclei requires an appreciation for, and at times some in-depth analysis of, curved spacetime. We highlight misconceptions surrounding the notion of coordinate transformation in general relativity as applied to metrics for rotating black holes that are beginning to increasingly appear in the literature. We emphasize that there is no coordinate transformation that can turn the metric of a rotating spacetime into that for a Schwarzschild spacetime, or more generally, that no coordinate transformation exists that can diagonalize the metric for a rotating spacetime. We caution against the notion of "local" coordinate transformation, which is often incorrectly associated with a global analysis of the spacetime.

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Authors: Mariafelicia De Laurentis

Date: 6 Apr 2010

Abstract: This review paper is devoted to the theory of orbits. We start with the discussion of the Newtonian problem of motion then we consider the relativistic problem of motion, in particular the PN approximation and the further gravitomagnetic corrections. Finally by a classification of orbits in accordance with the conditions of motion, we calculate the gravitational waves luminosity for different types of stellar encounters and orbits.

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Authors: D. Baskaran, L. P. Grishchuk, W. Zhao

Date: 6 Apr 2010

Abstract: This is a summary of presentations delivered at the OC1 parallel session "Primordial Gravitational Waves and the CMB" of the 12th Marcel Grossmann meeting in Paris, July 2009. The reports and discussions demonstrated significant progress that was achieved in theory and observations. It appears that the existing data provide some indications of the presence of gravitational wave contribution to the CMB anisotropies, while ongoing and planned observational efforts are likely to convert these indications into more confident statements about the actual detection.

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Authors: Patrick J. Sutton

Date: 26 May 2009

Abstract: In counting experiments, one can set an upper limit on the rate of a Poisson process based on a count of the number of events observed due to the process. In some experiments, one makes several counts of the number of events, using different instruments, different event detection algorithms, or observations over multiple time intervals. We demonstrate how to generalize the classical frequentist upper limit calculation to the case where multiple counts of events are made over one or more time intervals using several (not necessarily independent) procedures. We show how different choices of the rank ordering of possible outcomes in the space of counts correspond to applying different levels of significance to the various measurements. We propose an ordering that is matched to the sensitivity of the different measurement procedures and show that in typical cases it gives stronger upper limits than other choices. As an example, we show how this method can be applied to searches for gravitational-wave bursts, where multiple burst-detection algorithms analyse the same data set, and demonstrate how a single combined upper limit can be set on the gravitational-wave burst rate.

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Authors: Piotr T. Chruściel, Gregory J. Galloway, Daniel Pollack

Date: 7 Apr 2010

Abstract: We provide an introduction to selected significant advances in the mathematical understanding of Einstein's theory of gravitation which have taken place in recent years.

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Authors: LIGO Scientific Collaboration, Virgo Collaboration: B. P. Abbott, R. Abbott, F. Acernese, R. Adhikari, P. Ajith, B. Allen, G. Allen, M. Alshourbagy, R. S. Amin, S. B. Anderson, W. G. Anderson, F. Antonucci, S. Aoudia, M. A. Arain, M. Araya, H. Armandula, P. Armor, K. G. Arun, Y. Aso, S. Aston, P. Astone, P. Aufmuth, C. Aulbert, S. Babak, P. Baker, G. Ballardin, S. Ballmer, C. Barker, D. Barker, F. Barone, B. Barr, P. Barriga, L. Barsotti, M. Barsuglia, M. A. Barton, I. Bartos, R. Bassiri, M. Bastarrika, Th. S. Bauer, B. Behnke, M. Beker, M. Benacquista, J. Betzwieser, P. T. Beyersdorf, S. Bigotta, I. A. Bilenko, G. Billingsley, S. Birindelli, R. Biswas, M. A. Bizouard, E. Black, J. K. Blackburn, L. Blackburn, D. Blair, B. Bland, C. Boccara, T. P. Bodiya, L. Bogue, F. Bondu, L. Bonelli, R. Bork, V. Boschi, S. Bose, L. Bosi, S. Braccini, C. Bradaschia, P. R. Brady, V. B. Braginsky, J. E. Brau, D. O. Bridges, A. Brillet, M. Brinkmann, V. Brisson, C. Van Den Broeck, A. F. Brooks, D. A. Brown, A. Brummit, G. Brunet, R. Budzyński, T. Bulik, A. Bullington, H. J. Bulten, A. Buonanno, O. Burmeister, D. Buskulic, R. L. Byer, L. Cadonati, G. Cagnoli, E. Calloni, J. B. Camp, E. Campagna, J. Cannizzo, K. C. Cannon, B. Canuel, J. Cao, F. Carbognani, L. Cardenas, S. Caride, G. Castaldi, S. Caudill, M. Cavaglià, F. Cavalier, R. Cavalieri, G. Cella, C. Cepeda, E. Cesarini, T. Chalermsongsak, E. Chalkley, P. Charlton, E. Chassande-Mottin, S. Chatterji, S. Chelkowski, Y. Chen, A. Chincarini, N. Christensen, C. T. Y. Chung, D. Clark, J. Clark, J. H. Clayton, F. Cleva, E. Coccia, T. Cokelaer, C. N. Colacino, J. Colas, A. Colla, M. Colombini, R. Conte, D. Cook, T. R. C. Corbitt, C. Corda, N. Cornish, A. Corsi, J.-P. Coulon, D. Coward, D. C. Coyne, J. D. E. Creighton, T. D. Creighton, A. M. Cruise, R. M. Culter, A. Cumming, L. Cunningham, E. Cuoco, S. L. Danilishin, S. D'Antonio, K. Danzmann, A. Dari, V. Dattilo, B. Daudert, M. Davier, G. Davies, E. J. Daw, R. Day, R. De Rosa, D. DeBra, J. Degallaix, M. del Prete, V. Dergachev, S. Desai, R. DeSalvo, S. Dhurandhar, L. Di Fiore, A. Di Lieto, M. Di Paolo Emilio, A. Di Virgilio, M. Díaz, A. Dietz, F. Donovan, K. L. Dooley, E. E. Doomes, M. Drago, R. W. P. Drever, J. Dueck, I. Duke, J.-C. Dumas, J. G. Dwyer, C. Echols, M. Edgar, M. Edwards, A. Effler, P. Ehrens, E. Espinoza, T. Etzel, M. Evans, T. Evans, V. Fafone, S. Fairhurst, Y. Faltas, Y. Fan, D. Fazi, H. Fehrmann, I. Ferrante, F. Fidecaro, L. S. Finn, I. Fiori, R. Flaminio, K. Flasch, S. Foley, C. Forrest, N. Fotopoulos, J.-D. Fournier, J. Franc, A. Franzen, S. Frasca, F. Frasconi, M. Frede, M. Frei, Z. Frei, A. Freise, R. Frey, T. Fricke, P. Fritschel, V. V. Frolov, M. Fyffe, V. Galdi, L. Gammaitoni, J. A. Garofoli, F. Garufi, G. Gemme, E. Genin, A. Gennai, I. Gholami, J. A. Giaime, S. Giampanis, K. D. Giardina, A. Giazotto, K. Goda, E. Goetz, L. M. Goggin, G. González, M. L. Gorodetsky, S. Goeßzetler, S. Goßler, R. Gouaty, M. Granata, V. Granata, A. Grant, S. Gras, C. Gray, M. Gray, R. J. S. Greenhalgh, A. M. Gretarsson, C. Greverie, F. Grimaldi, R. Grosso, H. Grote, S. Grunewald, M. Guenther, G. Guidi, E. K. Gustafson, R. Gustafson, B. Hage, J. M. Hallam, D. Hammer, G. D. Hammond, C. Hanna, J. Hanson, J. Harms, G. M. Harry, I. W. Harry, E. D. Harstad, K. Haughian, K. Hayama, J. Heefner, H. Heitmann, P. Hello, I. S. Heng, A. Heptonstall, M. Hewitson, S. Hild, E. Hirose, D. Hoak, K. A. Hodge, K. Holt, D. J. Hosken, J. Hough, D. Hoyland, D. Huet, B. Hughey, S. H. Huttner, D. R. Ingram, T. Isogai, M. Ito, A. Ivanov, P. Jaranowski, B. Johnson, W. W. Johnson, D. I. Jones, G. Jones, R. Jones, L. Sancho de la Jordana, L. Ju, P. Kalmus, V. Kalogera, S. Kandhasamy, J. Kanner, D. Kasprzyk, E. Katsavounidis, K. Kawabe, S. Kawamura, F. Kawazoe, W. Kells, D. G. Keppel, A. Khalaidovski, F. Y. Khalili, R. Khan, E. Khazanov, P. King, J. S. Kissel, S. Klimenko, K. Kokeyama, V. Kondrashov, R. Kopparapu, S. Koranda, I. Kowalska, D. Kozak, B. Krishnan, A. Królak, R. Kumar, P. Kwee, P. La Penna, P. K. Lam, M. Landry, B. Lantz, A. Lazzarini, H. Lei, M. Lei, N. Leindecker, I. Leonor, N. Leroy, N. Letendre, C. Li, H. Lin, P. E. Lindquist, T. B. Littenberg, N. A. Lockerbie, D. Lodhia, M. Longo, M. Lorenzini, V. Loriette, M. Lormand, G. Losurdo, P. Lu, M. Lubinski, A. Lucianetti, H. Lück, B. Machenschalk, M. MacInnis, J.-M. Mackowski, M. Mageswaran, K. Mailand, E. Majorana, N. Man, I. Mandel, V. Mandic, M. Mantovani, F. Marchesoni, F. Marion, S. Márka, Z. Márka, A. Markosyan, J. Markowitz, E. Maros, J. Marque, F. Martelli, I. W. Martin, R. M. Martin, J. N. Marx, K. Mason, A. Masserot, F. Matichard, L. Matone, R. A. Matzner, N. Mavalvala, R. McCarthy, D. E. McClelland, S. C. McGuire, M. McHugh, G. McIntyre, D. J. A. McKechan, K. McKenzie, M. Mehmet, A. Melatos, A. C. Melissinos, G. Mendell, D. F. Menéndez, F. Menzinger, R. A. Mercer, S. Meshkov, C. Messenger, M. S. Meyer, C. Michel, L. Milano, J. Miller, J. Minelli, Y. Minenkov, Y. Mino, V. P. Mitrofanov, G. Mitselmakher, R. Mittleman, O. Miyakawa, B. Moe, M. Mohan, S. D. Mohanty, S. R. P. Mohapatra, J. Moreau, G. Moreno, N. Morgado, A. Morgia, T. Morioka, K. Mors, S. Mosca, V. Moscatelli, K. Mossavi, B. Mours, C. MowLowry, G. Mueller, D. Muhammad, H. zur Mühlen, S. Mukherjee, H. Mukhopadhyay, A. Mullavey, H. Müller-Ebhardt, J. Munch, P. G. Murray, E. Myers, J. Myers, T. Nash, J. Nelson, I. Neri, G. Newton, A. Nishizawa, F. Nocera, K. Numata, E. Ochsner, J. O'Dell, G. H. Ogin, B. O'Reilly, R. O'Shaughnessy, D. J. Ottaway, R. S. Ottens, H. Overmier, B. J. Owen, G. Pagliaroli, C. Palomba, Y. Pan, C. Pankow, F. Paoletti, M. A. Papa, V. Parameshwaraiah, S. Pardi, A. Pasqualetti, R. Passaquieti, D. Passuello, P. Patel, M. Pedraza, S. Penn, A. Perreca, G. Persichetti, M. Pichot, F. Piergiovanni, V. Pierro, M. Pietka, L. Pinard, I. M. Pinto, M. Pitkin, H. J. Pletsch, M. V. Plissi, R. Poggiani, F. Postiglione, M. Prato, M. Principe, R. Prix, G.A. Prodi, L. 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Sinha, A. M. Sintes, B. J. J. Slagmolen, J. Slutsky, M. V. van der Sluys, J. R. Smith, M. R. Smith, N. D. Smith, K. Somiya, B. Sorazu, A. Stein, L. C. Stein, S. Steplewski, A. Stochino, R. Stone, K. A. Strain, S. Strigin, A. Stroeer, R. Sturani, A. L. Stuver, T. Z. Summerscales, K. -X. Sun, M. Sung, Patrick J. Sutton, B. Swinkels, G. P. Szokoly, D. Talukder, L. Tang, D. B. Tanner, S. P. Tarabrin, J. R. Taylor, R. Taylor, R. Terenzi, J. Thacker, K. A. Thorne, K. S. Thorne, A. Thüring, K. V. Tokmakov, A. Toncelli, M. Tonelli, C. Torres, C. Torrie, E. Tournefier, F. Travasso, G. Traylor, M. Trias, J. Trummer, D. Ugolini, J. Ulmen, K. Urbanek, H. Vahlbruch, G. Vajente, M. Vallisneri, J.F.J. van den Brand, S. van der Putten, S. Vass, R. Vaulin, M. Vavoulidis, A. Vecchio, G. Vedovato, A. A. van Veggel, J. Veitch, P. Veitch, C. Veltkamp, D. Verkindt, F. Vetrano, A. Viceré, A. Villar, J.-Y. Vinet, H. Vocca, C. Vorvick, S. P. Vyachanin, S. J. Waldman, L. Wallace, R. L. Ward, M. Was, A. Weidner, M. Weinert, A. J. Weinstein, R. Weiss, L. Wen, S. Wen, K. Wette, J. T. Whelan, S. E. Whitcomb, B. F. Whiting, C. Wilkinson, P. A. Willems, H. R. Williams, L. Williams, B. Willke, I. Wilmut, L. Winkelmann, W. Winkler, C. C. Wipf, A. G. Wiseman, G. Woan, R. Wooley, J. Worden, W. Wu, I. Yakushin, H. Yamamoto, Z. Yan, S. Yoshida, M. Yvert, M. Zanolin, J. Zhang, L. Zhang, C. Zhao, N. Zotov, M. E. Zucker, J. Zweizig

Date: 26 Aug 2009

Abstract: We present the results of a search for gravitational-wave bursts associated with 137 gamma-ray bursts (GRBs) that were detected by satellite-based gamma-ray experiments during the fifth LIGO science run and first Virgo science run. The data used in this analysis were collected from 2005 November 4 to 2007 October 1, and most of the GRB triggers were from the Swift satellite. The search uses a coherent network analysis method that takes into account the different locations and orientations of the interferometers at the three LIGO-Virgo sites. We find no evidence for gravitational-wave burst signals associated with this sample of GRBs. Using simulated short-duration (<1 s) waveforms, we set upper limits on the amplitude of gravitational waves associated with each GRB. We also place lower bounds on the distance to each GRB under the assumption of a fixed energy emission in gravitational waves, with typical limits of D ~ 15 Mpc (E_GWˆiso / 0.01 M_o cˆ2)ˆ½ for emission at frequencies around 150 Hz, where the LIGO-Virgo detector network has best sensitivity. We present astrophysical interpretations and implications of these results, and prospects for corresponding searches during future LIGO-Virgo runs.

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Authors: Sean T. McWilliams, Bernard J. Kelly, John G. Baker

Date: 6 Apr 2010

Abstract: Advances in the field of numerical relativity now make it possible to calculate the final, most powerful merger phase of binary black-hole coalescence for generic binaries. The state of the art has advanced well beyond the equal-mass case into the unequal-mass and spinning regions of parameter space. We present a study of the nonspinning portion of parameter space, primarily using an analytic waveform model tuned to available numerical data, with an emphasis on observational implications. We investigate the impact of varied mass ratio on merger signal-to-noise ratios (SNRs) for several detectors, and compare our results with expectations from the test-mass limit. We note a striking similarity of the waveform phasing of the merger waveform across the available mass ratios. Motivated by this, we calculate the match between our 1:1 (equal mass) and 4:1 mass-ratio waveforms during the merger as a function of location on the source sky, using a new formalism for the match that accounts for higher harmonics. This is an indicator of the amount of degeneracy in mass ratio for mergers of moderate-mass-ratio systems.

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Authors: J. Slutsky, L. Blackburn, D. A. Brown, L. Cadonati, J. Cain, M. Cavagli&#xe0;, S. Chatterji, N. Christensen, M. Coughlin, S. Desai, G. Gonz&#xe1;lez, T. Isogai, E. Katsavounidis, B. Rankins, T. Reed, K. Riles, P. Shawhan, J. R. Smith, N. Zotov, J. Zweizig

Date: 7 Apr 2010

Abstract: The LIGO detectors are sensitive to a variety of noise transients of non-astrophysical origin. Instrumental glitches and environmental disturbances increase the false alarm rate in the searches for gravitational waves. Using times already identified when the interferometers produced data of questionable quality, or when the channels that monitor the interferometer indicated non-stationarity, we have developed techniques to safely and effectively veto false triggers from the compact binary coalescences (CBCs) search pipeline.

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Authors: Drew Keppel, P. Ajith

Date: 2 Apr 2010

Abstract: We study how well the mass of the graviton can be constrained from gravitational-wave (GW) observations of coalescing binary black holes. Whereas the previous investigations employed post-Newtonian (PN) templates describing only the inspiral part of the signal, the recent progress in analytical and numerical relativity has provided analytical waveform templates coherently describing the inspiral-merger-ringdown (IMR) signals. We show that a search for binary black holes employing IMR templates will be able to constrain the mass of the graviton much more accurately (about an order of magnitude) than a search employing PN templates. The best expected bound from GW observatories (lambda_g > 7.8 x 10ˆ13 km from Adv. LIGO, lambda_g > 7.1 x 10ˆ14 km from Einstein Telescope, and lambda_g > 5.9 x 10ˆ17 km from LISA) are several orders-of-magnitude better than the best available model-independent bound (lambda_g > 2.8 x 10ˆ12 km, from Solar system tests). Most importantly, GW observations will provide the first constraints from the highly dynamical, strong-field regime of gravity.

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Authors: Piotr Jaranowski, Andrzej Kr&#xf3;lak

Date: 2 Apr 2010

Abstract: In searches for gravitational waves emitted by known isolated pulsars in data collected by a detector one can assume that the frequency of the wave, its spindown parameters, and the position of the source in the sky are known, so the almost monochromatic gravitational-wave signal we are looking for depends on at most four parameters: overall amplitude, initial phase, polarization angle, and inclination angle of the pulsar's rotation axis with respect to the line of sight. We derive two statistics by means of which one can test whether data contains such gravitational-wave signal: the $\mathcal{G}$-statistic for signals which depend on only two unknown parameters (overall amplitude and initial phase), and the $\mathcal{F}$-statistic for signals depending on all four parameters. We study, by means of the Fisher matrix, the theoretical accuracy of the maximum-likelihood estimators of the signal's parameters and we present the results of the Monte Carlo simulations we performed to test the accuracy of these estimators.

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