**Authors**: Giuseppe Pucacco, Massimo Bassan, Massimo Visco

**Date**: 17 May 2010

**Abstract**: We investigate autonomous perturbations on the orbits of LISA, namely the effects produced by fields that can be expressed only in terms of the position, but not of time in the Hill frame. This first step in the study of the LISA orbits has been the subject of recent papers which implement analytical techniques based on a "post-epicyclic" approximation in the Hill frame to find optimal unperturbed orbits. The natural step forward is to analyze the perturbations to purely Keplerian orbits. In the present work a particular emphasis is put on the tidal field of the Earth assumed to be stationary in the Hill frame. An accurate interpretation of the global structure of the perturbed solution sheds light on possible implications on injection in orbit when the time base-line of the mission is longer than that assumed in previous papers. Other relevant classes of autonomous perturbations are those given by the corrections to the Solar field responsible for a slow precession and a global stationary field, associated to sources like the interplanetary dust or a local dark matter component. The inclusion of simple linear contributions in the expansion of these fields produces secular solutions that can be compared with the measurements and possibly used to evaluate some morphological property of the perturbing components.

1005.2976
(/preprints)

2010-05-24, 12:11
**[edit]**

**Authors**: Pau Amaro-Seoane, Bernard Schutz, Miguel Preto

**Date**: 21 May 2010

**Abstract**: GW Notes was born from the need for a journal where the distinct communities involved in gravitation wave research might gather. While these three communities - Astrophysics, General Relativity and Data Analysis - have made significant collaborative progress over recent years, we believe that it is indispensable to future advancement that they draw closer, and that they speak a common idiom. For this GW Notes issue we have approached Miguel Preto (Heidelberg University) to expand a recent work on how stars distribute around massive black holes for our highlight article.

1005.4048
(/preprints)

2010-05-24, 12:11
**[edit]**

**Authors**: Eric Chassande-Mottin, Miriam Miele, Satya Mohapatra, Laura Cadonati

**Date**: 12 May 2010

**Abstract**: Gravitational Wave (GW) burst detection algorithms typically rely on the hypothesis that the burst signal is "locally stationary", that is it changes slowly with frequency. Under this assumption, the signal can be decomposed into a small number of wavelets with constant frequency. This justifies the use of a family of sine-Gaussian templates in the Omega pipeline, one of the algorithms used in LIGO-Virgo burst searches. However there are plausible scenarios where the burst frequency evolves rapidly, such as in the merger phase of a binary black hole and/or neutron star coalescence. In those cases, the local stationarity of sine-Gaussians induces performance losses, due to the mismatch between the template and the actual signal. We propose an extension of the Omega pipeline based on chirplet-like templates. Chirplets incorporate an additional parameter, the chirp rate, to control the frequency variation. In this paper, we show that the Omega pipeline can easily be extended to include a chirplet template bank. We illustrate the method on a simulated data set, with a family of phenomenological binary black-hole coalescence waveforms embedded into Gaussian LIGO/Virgo-like noise. Chirplet-like templates result in an enhancement of the measured signal-to-noise ratio.

1005.2876
(/preprints)

2010-05-24, 12:11
**[edit]**

**Authors**: Naoki Seto, Takayuki Muto

**Date**: 18 May 2010

**Abstract**: We show that a massive black hole binary might resonantly trap a small third body (e.g. a neutron star) down to a stage when the binary becomes relativistic due to its orbital decay by gravitational radiation. The final fate of the third body would be quite interesting for relativistic astrophysics. For example, the parent binary could expel the third body with a velocity more than 10% of the speed of light. We also discuss the implications of this three-body system for direct gravitational wave observation.

1005.3114
(/preprints)

2010-05-24, 12:11
**[edit]**

**Authors**: Jiri Kovar, Ondrej Kopacek, Vladimir Karas, Zdenek Stuchlik

**Date**: 18 May 2010

**Abstract**: Off-equatorial circular orbits with constant latitudes (halo orbits) of electrically charged particles exist near compact objects. In the previous paper, we discussed this kind of motion and demonstrated the existence of minima of the two-dimensional effective potential which correspond to the stable halo orbits. Here, we relax previous assumptions of the pseudo-Newtonian approach for the gravitational field of the central body and study properties of the halo orbits in detail. Within the general relativistic approach, we carry out our calculations in two cases. Firstly, we examine the case of a rotating magnetic compact star. Assuming that the magnetic field axis and the rotation axis are aligned with each other, we study the orientation of motion along the stable halo orbits. In the poloidal plane, we also discuss shapes of the related effective potential halo lobes where the general off-equatorial motion can be bound. Then we focus on the halo orbits near a Kerr black hole immersed in an asymptotically uniform magnetic field of external origin. We demonstrate that, in both the cases considered, the lobes exhibit two different regimes, namely, one where completely disjoint lobes occur symmetrically above and below the equatorial plane, and another where the lobes are joined across the plane. A possible application of the model concerns the structure of putative circumpulsar discs consisting of dust particles. We suggest that the particles can acquire a small (but non-zero) net electric charge, and this drives them to form the halo lobes.

1005.3270
(/preprints)

2010-05-24, 12:11
**[edit]**

**Authors**: L. Santamaria, F. Ohme, P. Ajith, B. Bruegmann, N. Dorband, M. Hannam, S. Husa, P. Moesta, D. Pollney, C. Reisswig, J. Seiler, B. Krishnan

**Date**: 18 May 2010

**Abstract**: We present a new phenomenological gravitational waveform model for he inspiral and coalescence of non-precessing spinning black hole binaries. Our approach is based on a frequency domain matching of post-Newtonian inspiral waveforms with numerical relativity based binary black hole coalescence waveforms. We quantify the various possible sources of systematic errors that arise in matching post-Newtonian and numerical relativity waveforms, and we use a matching criteria based on minimizing these errors; we find that the dominant source of errors are those in the post-Newtonian waveforms near the merger. An analytical formula for the dominant mode of the gravitational radiation of non-precessing black hole binaries is presented that captures the phenomenology of the hybrid waveforms. Its implementation in the current searches for gravitational waves should allow cross-checks of other inspiral-merger-ringdown waveform families and improve the reach of gravitational wave searches.

1005.3306
(/preprints)

2010-05-24, 12:11
**[edit]**

**Authors**: Ivan Zalamea, Kristen Menou, Andrei M. Beloborodov

**Date**: 21 May 2010

**Abstract**: White dwarfs inspiraling into black holes of mass $\MBH\simgt 10ˆ5M_\odot$ are detectable sources of gravitational waves in the LISA band. In many of these events, the white dwarf begins to lose mass during the main observational phase of the inspiral. The mass loss starts gently and can last for thousands of orbits. The white dwarf matter overflows the Roche lobe through the $L_1$ point at each pericenter passage and the mass loss repeats periodically. The process occurs very close to the black hole and the released gas can accrete, potentially creating a bright source of radiation with luminosity close to the Eddington limit, $L\sim 10ˆ{43}$ erg s$ˆ{-1}$. This class of inspirals offers a promising scenario for dual detections of gravitational waves and electromagnetic radiation.

1005.3987
(/preprints)

2010-05-24, 12:11
**[edit]**

**Authors**: Nicolas Yunes, Richard O'Shaughnessy, Benjamin J. Owen, Stephon Alexander

**Date**: 18 May 2010

**Abstract**: Gravitational parity violation is a possibility motivated by particle physics, string theory and loop quantum gravity. One effect of it is amplitude birefringence of gravitational waves, whereby left and right circularly-polarized waves propagate at the same speed but with different amplitude evolution. Here we propose a test of this effect through coincident observations of gravitational waves and short gamma-ray bursts from binary mergers involving neutron stars. Such gravitational waves are highly left or right circularly-polarized due to the geometry of the merger. Using localization information from the gamma-ray burst, ground-based gravitational wave detectors can measure the distance to the source with reasonable accuracy. An electromagnetic determination of the redshift from an afterglow or host galaxy yields an independent measure of this distance. Gravitational parity violation would manifest itself as a discrepancy between these two distance measurements. We exemplify such a test by considering one specific effective theory that leads to such gravitational parity-violation, Chern-Simons gravity. We show that the advanced LIGO-Virgo network and all-sky gamma-ray telescopes can be sensitive to the propagating sector of Chern-Simons gravitational parity violation to a level roughly two orders of magnitude better than current stationary constraints from the LAGEOS satellites.

1005.3310
(/preprints)

2010-05-24, 12:11
**[edit]**

**Authors**: Christian Trenkel, Steve Kemble, Neil Bevis, Joao Magueijo

**Date**: 8 Jan 2010

**Abstract**: We suggest that LISA Pathfinder could be used to subject TEVES, and in particular the non-relativistic MOND phenomenology it incorporates, to a direct, controlled experimental test, in just a few years' time. The basic concept is to fly LISA Pathfinder through the region around the Sun-Earth saddle point, following its nominal mission, in order to look for anomalous gravity gradients. We examine various strategies to reach the saddle point, and conclude that the preferred strategy, resulting in relatively short transfer times of order one year, probably involves a lunar fly-by. We present robust estimates of the MOND gravity gradients that LISA Pathfinder should be exposed to, and conclude that if the gradiometer on-board the spacecraft achieves its nominal performance, these gradients will not just be detected, but measured and characterised in some detail, should they exist. Conversely, given the large predicted signal based on standard assumptions, a null result would most likely spell the end of TEVES/MOND.

1001.1303
(/preprints)

2010-05-24, 11:17
**[edit]**

**Authors**: L. Veréb, Z. Keresztes, P. Raffai, Zs. Udvari, M. Tápai, L. Á. Gergely

**Date**: 12 May 2010

**Abstract**: We investigate whether the recovery chances of highly spinning waveforms by matched filtering with randomly chosen spinning waveforms generated with the LAL package are improved by a cross-correlation of the simulated output of the L1 and H1 LIGO detectors. We find that a properly defined correlated overlap improves the mass estimates and enhances the recovery of spin angles.

1005.2101
(/preprints)

2010-05-17, 19:27
**[edit]**

**Authors**: Tim Johannsen (Arizona), Dimitrios Psaltis (Arizona)

**Date**: 11 May 2010

**Abstract**: According to the no-hair theorem, all astrophysical black holes are fully described by their masses and spins. This theorem can be tested observationally by measuring (at least) three different multipole moments of the spacetimes of black holes. In this paper, we analyze images of black holes within a framework that allows us to calculate observables in the electromagnetic spectrum as a function of the mass, spin, and, independently, the quadrupole moment of a black hole. We show that a deviation of the quadrupole moment from the expected Kerr value leads to images of black holes that are either prolate or oblate depending on the sign and magnitude of the deviation. In addition, there is a ring-like structure around the black-hole shadow with a diameter of about 10 black-hole masses that is substantially brighter than the image of the underlying accretion flow and that is independent of the astrophysical details of accretion flow models. We show that the shape of this ring depends directly on the mass, spin, and quadrupole moment of the black hole and can be used for an independent measurement of all three parameters. In particular, we demonstrate that this ring is highly circular for a Kerr black hole with a spin a<0.9M, independent of the observer's inclination, but becomes elliptical and asymmetric if the no-hair theorem is violated. Near-future very-long baseline interferometric observations of Sgr A* will image this ring and allow for an observational test of the no-hair theorem.

1005.1931
(/preprints)

2010-05-17, 19:27
**[edit]**

**Authors**: Glenn de Vine, Brent Ware, Kirk McKenzie, Robert E. Spero, William M. Klipstein, Daniel A. Shaddock

**Date**: 12 May 2010

**Abstract**: We report on the first demonstration of time-delay interferometry (TDI) for LISA, the Laser Interferometer Space Antenna. TDI was implemented in a laboratory experiment designed to mimic the noise couplings that will occur in LISA. TDI suppressed laser frequency noise by approximately 10ˆ9 and clock phase noise by 6x10ˆ4, recovering the intrinsic displacement noise floor of our laboratory test bed. This removal of laser frequency noise and clock phase noise in post-processing marks the first experimental validation of the LISA measurement scheme.

1005.2176
(/preprints)

2010-05-17, 19:27
**[edit]**

**Authors**: Antoine Klein, Philippe Jetzer

**Date**: 12 May 2010

**Abstract**: We compute here the spin-orbit and spin-spin couplings needed for an accurate computation of the phasing of gravitational waves emitted by comparable-mass binaries on eccentric orbits at the second post-Newtonian (PN) order. We use a quasi-Keplerian parametrization of the orbit free of divergencies in the zero eccentricity limit. We find that spin-spin couplings induce a residual eccentricity for coalescing binaries at 2PN, of the order of $10ˆ{-4}$-$10ˆ{-3}$ for supermassive black hole binaries in the LISA band. Spin-orbit precession also induces a non-trivial pattern in the evolution of the eccentricity, which could help to reduce the errors on the determination of the eccentricity and spins in a gravitational wave measurement.

1005.2046
(/preprints)

2010-05-17, 19:27
**[edit]**

**Authors**: D. R. B. Yardley, G. B. Hobbs, F. A. Jenet, J. P. W. Verbiest, Z. L. Wen, R. N. Manchester, W. A. Coles, W. van Straten, M. Bailes, N. D. R. Bhat, S. Burke-Spolaor, D. J. Champion, A. W. Hotan, J. M. Sarkissian

**Date**: 10 May 2010

**Abstract**: We present the sensitivity of the Parkes Pulsar Timing Array to gravitational waves emitted by individual super-massive black-hole binary systems in the early phases of coalescing at the cores of merged galaxies. Our analysis includes a detailed study of the effects of fitting a pulsar timing model to non-white timing residuals. Pulsar timing is sensitive at nanoHertz frequencies and hence complementary to LIGO and LISA. We place a sky-averaged constraint on the merger rate of nearby ($z < 0.6$) black-hole binaries in the early phases of coalescence with a chirp mass of $10ˆ{10}\,\rmn{M}_\odot$ of less than one merger every seven years. The prospects for future gravitational-wave astronomy of this type with the proposed Square Kilometre Array telescope are discussed.

1005.1667
(/preprints)

2010-05-12, 09:11
**[edit]**

**Authors**: Raffaella Schneider, Stefania Marassi, Valeria Ferrari

**Date**: 6 May 2010

**Abstract**: Astrophysical sources emit gravitational waves in a large variety of processes occurred since the beginning of star and galaxy formation. These waves permeate our high redshift Universe, and form a background which is the result of the superposition of different components, each associated to a specific astrophysical process. Each component has different spectral properties and features that it is important to investigate in view of a possible, future detection. In this contribution, we will review recent theoretical predictions for backgrounds produced by extragalactic sources and discuss their detectability with current and future gravitational wave observatories.

1005.0977
(/preprints)

2010-05-10, 09:18
**[edit]**

**Authors**: Keisuke Taniguchi, Masaru Shibata

**Date**: 6 May 2010

**Abstract**: Quasi-equilibrium sequences of binary neutron stars are constructed for a variety of equations of state in general relativity. Einstein's constraint equations in the Isenberg-Wilson-Mathews approximation are solved together with the relativistic equations of hydrostationary equilibrium under the assumption of irrotational flow. We focus on unequal-mass sequences as well as equal-mass sequences, and compare those results. We investigate the behavior of the binding energy and total angular momentum along a quasi-equilibrium sequence, the endpoint of sequences, and the orbital angular velocity as a function of time, changing the mass ratio, the total mass of the binary system, and the equation of state of a neutron star. It is found that the orbital angular velocity at the mass-shedding limit can be determined by an empirical formula derived from an analytic estimation. We also provide tables for 160 sequences which will be useful as a guideline of numerical simulations for the inspiral and merger performed in the near future.

1005.0958
(/preprints)

2010-05-10, 09:18
**[edit]**

**Authors**: Kipp Cannon, Adrian Chapman, Chad Hanna, Drew Keppel, Antony C. Searle, Alan J. Weinstein

**Date**: 30 Apr 2010

**Abstract**: We investigate the application of the singular value decomposition to compact-binary, gravitational-wave data-analysis. We find that the truncated singular value decomposition reduces the number of filters required to analyze a given region of parameter space of compact binary coalescence waveforms by an order of magnitude with high reconstruction accuracy. We also compute an analytic expression for the expected signal-loss due to the singular value decomposition truncation.

1005.0012
(/preprints)

2010-05-06, 17:08
**[edit]**

**Authors**: Chandra Kant Mishra, K. G. Arun, Bala R. Iyer, B. S. Sathyaprakash

**Date**: 3 May 2010

**Abstract**: General relativity has very specific predictions for the gravitational waveforms from inspiralling compact binaries obtained using the post-Newtonian (PN) approximation. We investigate the extent to which the measurement of the PN coefficients, possible with the second generation gravitational wave detectors such as the Advanced Laser Interferometer Gravitational-Wave Observatory (LIGO) and the third generation gravitational-wave detectors such as the Einstein Telescope (ET), could be used to test post-Newtonian theory and to put bounds on a class of theories which differ from general relativity in a parametrized sense. We demonstrate this possibility by employing the best inspiralling waveform models for nonspinning compact binaries which is 3.5PN accurate in phase and 3PN in amplitude. Advanced LIGO can test the theory at 1.5PN and thus the leading tail term. Future observations of stellar mass black hole binaries by ET can test the consistency between the various PN coefficients in the GW phasing over the mass range of $11$-$44 M_\odot$. The choice of the lower frequency cutoff is important for testing post-Newtonian theory using the ET.

1005.0304
(/preprints)

2010-05-06, 17:08
**[edit]**

**Authors**: Sergey Postnikov, Madappa Prakash, James Lattimer

**Date**: 28 Apr 2010

**Abstract**: Gravitational waves from the final stages of inspiralling binary neutron stars are expected to be one of the most important sources for ground-based gravitational wave detectors. The masses of the components are determinable from the orbital and chirp frequencies during the early part of the evolution during which tidal effects provide small correction; however, during this phase the signal is relatively clean. The accumulated phase shift due to tidal corrections is characterized by a single quantity, the Love number, which is sensitive to the compactness parameter M/R and the star's internal structure, and its determination could constrain the star's radius. We show that the Love number of normal neutron stars are much different from those of self-bound strange quark matter stars and could therefore provide an important way to distinguish between these two classes of stars.

1004.5098
(/preprints)

2010-05-06, 17:07
**[edit]**

**Authors**: R. Sturani, S. Fischetti, L. Cadonati, G. M. Guidi, J. Healy, D. Shoemaker, A. Viceré

**Date**: 4 May 2010

**Abstract**: The quest for gravitational waves from coalescing binaries is customarily performed by the LIGO-Virgo collaboration via matched filtering, which requires a detailed knowledge of the signal. Complete analytical coalescence waveforms are currently available only for the non-precessing binary systems. In this paper we introduce complete phenomenological waveforms for the dominant quadrupolar mode of generically spinning systems. These waveforms are constructed by bridging the gap between the analytically known inspiral phase, described by spin Taylor (T4) approximants in the restricted waveform approximation, and the ring-down phase through a phenomenological intermediate phase, calibrated by comparison with specific, numerically generated waveforms, describing equal mass systems with dimension-less spin magnitudes equal to 0.6. The overlap integral between numerical and phenomenological waveforms ranges between 0.95 and 0.99.

1005.0551
(/preprints)

2010-05-06, 17:06
**[edit]**

**Authors**: Holger J. Pletsch

**Date**: 3 May 2010

**Abstract**: Continuous gravitational-wave (CW) signals such as emitted by spinning neutron stars are an important target class for current detectors. However, the enormous computational demand prohibits fully-coherent broadband all-sky searches for prior unknown CW sources over wide ranges of parameter space and for year-long observation times. More efficient hierarchical "semicoherent" search strategies divide the data into segments much shorter than one year, which are analyzed coherently; then detection statistics from different segments are combined incoherently. To optimally perform the incoherent combination, understanding of the underlying parameter-space structure is requisite. This problem is addressed here by using new coordinates on the parameter space, which yield the first analytical parameter-space metric for the incoherent combination step. This semicoherent metric applies to broadband all-sky surveys (also embedding directed searches at fixed sky position) for isolated CW sources. Furthermore, the additional metric resolution attained through the combination of segments is studied. From the search parameters (sky position, frequency and frequency derivatives), solely the metric resolution in the frequency derivatives is found to significantly increase with the number of segments.

1005.0395
(/preprints)

2010-05-06, 17:06
**[edit]**

**Authors**: Konstantin N Yakunin, Pedro Marronetti, Anthony Mezzacappa, Stephen W Bruenn, Ching-Tsai Lee, M Austin Chertkow, W Raphael Hix, John M Blondin, Eric J Lentz, O E Bronson Messer, Shin'ichirou Yoshida

**Date**: 5 May 2010

**Abstract**: We present the gravitational wave signatures for a suite of axisymmetric core collapse supernova models with progenitors masses between 12 and 25 sollar masses. These models are distinguished by the fact they explode and contain essential physics (in particular, multi-frequency neutrino transport and general relativity) needed for a more realistic description. Thus, we are able to compute complete waveforms (i.e., through explosion) based on non-parameterized, first-principles models. This is essential if the waveform amplitudes and time scales are to be computed more precisely. Fourier decomposition shows that the peak in the AdvLIGO-observable component of the gravitational wave signature stems from the SASI. The fundamental limitation of these models is in their imposition of axisymmetry. Further progress will require counterpart three-dimensional models.

1005.0779
(/preprints)

2010-05-06, 17:05
**[edit]**

**Authors**: Michael Kesden, Guglielmo Lockhart, E. Sterl Phinney

**Date**: 4 May 2010

**Abstract**: Black holes of mass M must have a spin angular momentum S below the Kerr limit chi = S/Mˆ2 < 1, but whether astrophysical black holes can attain this limiting spin depends on their accretion history. Gas accretion from a thin disk limits the black-hole spin to chi_gas < 0.9980 +- 0.0002, as electromagnetic radiation from this disk with retrograde angular momentum is preferentially absorbed by the black hole. Extrapolation of numerical-relativity simulations of equal-mass binary black-hole mergers to maximum initial spins suggests these mergers yield a maximum spin chi_eq < 0.95. Here we show that for smaller mass ratios q = m/M << 1, the superradiant extraction of angular momentum from the larger black hole imposes a fundamental limit chi_lim < 0.9979 +- 0.0001 on the final black-hole spin even in the test-particle limit q -> 0 of binary black-hole mergers. The nearly equal values of chi_gas and chi_lim imply that measurement of supermassive black-hole spins cannot distinguish a black hole built by gas accretion from one assembled by the gravitational inspiral of a disk of compact stellar remnants. We also show how superradiant scattering alters the mass and spin predicted by models derived from extrapolating test-particle mergers to finite mass ratios.

1005.0627
(/preprints)

2010-05-06, 17:05
**[edit]**

**Authors**: Delphine L. Perrodin

**Date**: 4 May 2010

**Abstract**: We study the gravitational dynamics in the early inspiral phase of coalescing compact binaries using Non-Relativistic General Relativity (NRGR) - an effective field theory formalism based on the post-newtonian expansion, but which provides a consistent lagrangian framework and a systematic way in which to study binary dynamics and gravitational wave emission. We calculate in this framework the spin-orbit correction to the newtonian potential at 2.5 PN.

1005.0634
(/preprints)

2010-05-06, 17:04
**[edit]**

© M. Vallisneri 2012 — last modified on 2010/01/29

*Tantum in modicis, quantum in maximis*