[1105.5283] Testing String Theory with Gravitational Waves

Authors: Ruth Durrer, Jasper Hasenkamp

Date: 26 May 2011

Abstract: We provide a simple transfer function that considers the impact of an early matter dominated era on the gravitational wave background and show that string theory can be tested by observations of the gravitational wave background from inflation.

abs pdf

May 27, 2011

1105.5283 (/preprints)
2011-05-27, 21:56 [edit]


[1105.4370] Binary Neutron Star Mergers: Dependence on the Nuclear Equation of State

Authors: Kenta Hotokezaka, Koutarou Kyutoku, Hirotada Okawa, Masaru Shibata, Kenta Kiuchi

Date: 22 May 2011

Abstract: We perform a numerical-relativity simulation for the merger of binary neutron stars with 6 nuclear-theory-based equations of state (EOSs) described by piecewise polytropes. Our purpose is to explore the dependence of the dynamical behavior of the binary neutron star merger and resulting gravitational waveforms on the EOS of the supernuclear-density matter. The numerical results show that the merger process and the first outcome are classified into three types; (i) a black hole is promptly formed, (ii) a short-lived hypermassive neutron star (HMNS) is formed, (iii) a long-lived HMNS is formed. The type of the merger depends strongly on the EOS and on the total mass of the binaries. For the EOS with which the maximum mass is larger than 2Msun, the lifetime of the HMNS is longer than 10 ms for a total mass m_0=2.7Msun. A recent radio observation suggests that the maximum mass of spherical neutron stars is M_max \geq 1.97\pm 0.04Msun in one \sigma level. This fact and our results support the possible existence of a HMNS soon after the onset of the merger for a typical binary neutron star with m_0=2.7Msun. We also show that the torus mass surrounding the remnant black hole is correlated with the type of the merger process; the torus mass could be large, \geq 0.1Msun, in the case that a long-lived HMNS is formed. We also show that gravitational waves carry information of the merger process, the remnant, and the torus mass surrounding a black hole.

abs pdf

May 23, 2011

1105.4370 (/preprints)
2011-05-23, 22:34 [edit]


[1105.3735] Theoretical Aspects of Massive Gravity

Authors: Kurt Hinterbichler

Date: 18 May 2011

Abstract: Massive gravity has seen a resurgence of interest due to the recent realization that its traditional problems may be overcome, yielding an avenue for addressing important open questions such as the cosmological constant naturalness problem. The possibility of a massive graviton has been studied off and on for the past 70 years. During this time, curiosities such as the vDVZ discontinuity and the Boulware-Deser ghost were uncovered. We re-derive these results in a pedagogical manner, and develop the St\"ukelberg formalism to discuss them from the modern effective field theory viewpoint. We review recent progress of the last decade, including the dissolution of the vDVZ discontinuity via the Vainshtein screening mechanism, the existence of a consistent effective field theory with a stable hierarchy between the graviton mass and the cutoff, the existence of particular interactions which raise the maximal effective field theory cutoff, and strong hints that the higher cutoff theory is ghost free. In addition, we review some peculiarities of massive gravitons on curved space, novel theories in three dimensions, and examples of the emergence of a massive graviton from extra-dimensions and brane worlds.

abs pdf

May 23, 2011

1105.3735 (/preprints)
2011-05-23, 22:26 [edit]


[1105.3861] Comparing numerical and analytical calculations of post-ISCO ringdown amplitudes

Authors: Shahar Hadar, Barak Kol, Emanuele Berti, Vitor Cardoso

Date: 19 May 2011

Abstract: We numerically compute the ringdown amplitudes following the plunge of a particle from the innermost stable circular orbit (ISCO) of a Schwarzschild black hole in the extreme-mass ratio limit. We show that the ringdown amplitudes computed in this way are in good agreement with a recent analytical calculation arXiv:0911.3899.

abs pdf

May 20, 2011

1105.3861 (/preprints)
2011-05-20, 13:48 [edit]


[1105.3567] The importance of including small body spin effects in the modelling of extreme and intermediate mass-ratio inspirals

Authors: EA Huerta, Jonathan R Gair

Date: 18 May 2011

Abstract: We explore the ability of future low-frequency gravitational wave detectors to measure the spin of stellar mass and intermediate mass black holes that inspiral onto super-massive Kerr black holes (SMBHs). We develop a kludge waveform model based on the equations of motion derived by Saijo et al. [Phys Rev D 58, 064005, 1998] for spinning BH binaries, augmented with spin-orbit and spin-spin couplings taken from perturbative and post-Newtonian (PN) calculations, and the associated conservative self-force corrections, derived by comparison to PN results. We model the inspiral phase using accurate fluxes which include perturbative corrections for the spin of the inspiralling body, spin-spin couplings and higher-order fits to solutions of the Teukolsky equation. We present results of Monte Carlo simulations of parameter estimation errors and of the model errors that arise when we omit conservative corrections from the waveform template. For a source 5000+10ˆ6 solar mass observed with an SNR of 1000, LISA will be able to determine the two masses to within a fractional error of ~0.001, measure the SMBH spin magnitude, q, and the spin magnitude of the inspiralling BH to 0.0001, 10%, respectively, and determine the location of the source in the sky and the SMBH spin orientation to within 0.0001 steradians. For a 10+10ˆ6 solar mass system observed with SNR of 30, LISA will not be able to determine the spin magnitude of the inspiralling BH, although the measurement of the other waveform parameters is not significantly degraded by the presence of spin. The model errors which arise from ignoring conservative corrections become significant for mass-ratios above 0.0001, but including these corrections up to 2PN order may be sufficient to reduce these systematic errors to an acceptable level.

abs pdf

May 19, 2011

1105.3567 (/preprints)
2011-05-19, 15:25 [edit]


[1105.3191] A Metric for Rapidly Spinning Black Holes Suitable for Strong-Field Tests of the No-Hair Theorem

Authors: Tim Johannsen, Dimitrios Psaltis (Arizona)

Date: 16 May 2011

Abstract: According to the no-hair theorem, astrophysical black holes are uniquely characterized by their masses and spins and are described by the Kerr metric. Several parametric deviations from the Kerr metric have been suggested to study observational signatures in both the electromagnetic and gravitational-wave spectra that differ from the expected Kerr signals. Due to the no-hair theorem, however, such spacetimes cannot be regular everywhere outside the event horizons, if they are solutions to the Einstein field equations; they are often characterized by naked singularities or closed time-like loops in the regions of the spacetime that are accessible to an external observer. For observational tests of the no-hair theorem that involve phenomena in the vicinity of the circular photon orbit or the innermost stable circular orbit around a black hole, these pathologies limit the applicability of the metrics only to compact objects that do not spin rapidly. In this paper, we construct a Kerr-like metric which depends on a set of free parameters in addition to its mass and spin and which is regular everywhere outside of the event horizon. We derive expressions for the energy and angular momentum of a particle on a circular equatorial orbit around the black hole and compute the locations of the innermost stable circular orbit and the circular photon orbit. We demonstrate that these orbits change significantly for even moderate deviations from the Kerr metric. The properties of our metric make it an ideally suited spacetime to carry out strong-field tests of the no-hair theorem in the electromagnetic spectrum using the properties of accretion flows around astrophysical black holes of arbitrary spin.

abs pdf

May 18, 2011

1105.3191 (/preprints)
2011-05-18, 14:51 [edit]


[1105.1678] Gravitational waves from perturbed stars

Authors: Valeria Ferrari

Date: 9 May 2011

Abstract: Non radial oscillations of neutron stars are associated with the emission of gravitational waves. The characteristic frequencies of these oscillations can be computed using the theory of stellar perturbations, and they are shown to carry detailed information on the internal structure of the emitting source. Moreover, they appear to be encoded in various radiative processes, as for instance in the tail of the giant flares of Soft Gamma Repeaters. Thus, their determination is central to the theory of stellar perturbation. A viable approach to the problem consists in formulating this theory as a problem of resonant scattering of gravitational waves incident on the potential barrier generated by the spacetime curvature. This approach discloses some unexpected correspondences between the theory of stellar perturbations and the theory of quantum mechanics, and allows us to predict new relativistic effects.

abs pdf

May 17, 2011

1105.1678 (/preprints)
2011-05-17, 14:42 [edit]


[1105.2125] Gravitational waves and neutrino emission from the merger of binary neutron stars

Authors: Yuichiro Sekiguchi, Kenta Kiuchi, Koutarou Kyutoku, Masaru Shibata

Date: 11 May 2011

Abstract: Numerical simulations for the merger of binary neutron stars are performed in full general relativity incorporating a finite-temperature (Shen's) equation of state (EOS) and neutrino cooling for the first time. It is found that for this stiff EOS, a hypermassive neutron star (HMNS) with a long lifetime ($\gg 10$ ms) is the outcome for the total mass $\alt 3.0M_{\odot}$. It is shown that the typical total neutrino luminosity of the HMNS is $\sim 3$--$8\times 10ˆ{53}$ ergs/s and the effective amplitude of gravitational waves from the HMNS is 4--$6 \times 10ˆ{-22}$ at $f=2.1$--2.5 kHz for a source distance of 100 Mpc. We also present the neutrino luminosity curve when a black hole is formed for the first time.

abs pdf

May 17, 2011

1105.2125 (/preprints)
2011-05-17, 14:41 [edit]


[1105.2088] Gravitational Wave Tests of General Relativity with the Parameterized Post-Einsteinian Framework

Authors: Neil Cornish, Laura Sampson, Nico Yunes, Frans Pretorius

Date: 11 May 2011

Abstract: Gravitational wave astronomy has tremendous potential for studying extreme astrophysical phenomena and exploring fundamental physics. The waves produced by binary black hole mergers will provide a pristine environment in which to study strong field, dynamical gravity. Extracting detailed information about these systems requires accurate theoretical models of the gravitational wave signals. If gravity is not described by General Relativity, analyses that are based on waveforms derived from Einstein's field equations could result in parameter biases and a loss of detection efficiency. A new class of "parameterized post-Einsteinian" (ppE) waveforms has been proposed to cover this eventuality. Here we apply the ppE approach to simulated data from a network of advanced ground based interferometers (aLIGO/aVirgo) and from a future spaced based interferometer (LISA). Bayesian inference and model selection are used to investigate parameter biases, and to determine the level at which departures from general relativity can be detected. We find that in some cases the parameter biases from assuming the wrong theory can be severe. We also find that gravitational wave observations will beat the existing bounds on deviations from general relativity derived from the orbital decay of binary pulsars by a large margin across a wide swath of parameter space.

abs pdf

May 17, 2011

1105.2088 (/preprints)
2011-05-17, 14:41 [edit]


[1105.3184] Localizing compact binary inspirals on the sky using ground-based gravitational wave interferometers

Authors: Samaya M. Nissanke, Jonathan L. Sievers, Neal Dalal, Daniel E. Holz

Date: 16 May 2011

Abstract: The inspirals and mergers of compact binaries are among the most promising events for ground-based gravitational wave (GW) observatories. The detection of electromagnetic (EM) signals from these sources would provide complementary information to the GW signal. It is therefore important to determine the ability of gravitational-wave detectors to localize compact binaries on the sky, so that they can be matched to their EM counterparts. We use Markov Chain Monte Carlo techniques to study sky localization using networks of ground-based interferometers. Using a coherent-network analysis, we find that the LIGO-Virgo network can localize 50% of their ~8 sigma detected neutron star binaries to better than 50 sq.deg. with 95% confidence region. The addition of LCGT and LIGO-Australia improves this to 12 sq.deg.. Using a more conservative coincident detection threshold, we find that 50% of detected neutron star binaries are localized to 13 sq.deg. using the LIGO-Virgo network, and to 3 sq.deg. using the LIGO-Virgo-LCGT-LIGO-Australia network. Our findings suggest that the coordination of GW observatories and EM facilities offers great promise.

abs pdf

May 17, 2011

1105.3184 (/preprints)
2011-05-17, 14:09 [edit]


[1105.2959] Equatorial circular motion in Kerr spacetime

Authors: Daniela Pugliese, Hernando Quevedo, Remo Ruffini

Date: 15 May 2011

Abstract: We analyze the properties of circular orbits of test particles on the equatorial plane of a rotating central mass whose gravitational field is described by the Kerr spacetime. For rotating black holes and naked singularities we explore all the spatial regions where circular orbits can exist and analyze the behavior of the energy and the angular momentum of the corresponding test particles. In particular, we find all the radii at which a test particle can have zero angular momentum due to the repulsive gravity effects generated by naked singularities. We classify all the stability zones of circular orbits. It is shown that the geometric structure of the stability zones of black holes is completely different from that of naked singularities.

abs pdf

May 17, 2011

1105.2959 (/preprints)
2011-05-17, 14:08 [edit]


[1105.3175] Eccentric Black Hole-Neutron Star Mergers

Authors: Branson C. Stephens (1), William E. East (2), Frans Pretorius (2) ((1) UW-Milwaukee, (2) Princeton University)

Date: 16 May 2011

Abstract: Within the next few years gravitational waves (GWs) from merging black holes (BHs) and neutron stars (NSs) may be directly detected, making a thorough theoretical understanding of these systems a high priority. Such mergers are expected to result from primordial, quasi-circular BH-NS inspiral as well as dynamically formed capture binaries. The latter channel allows mergers with high eccentricity, resulting in a richer variety of outcomes. We perform general relativistic simulations of BH-NS interactions with a range of impact parameters, and find significant variation in the properties of these events that have potentially observable consequences, namely the GW signature, remnant accretion disk mass, and amount of unbound material.

abs pdf

May 17, 2011

1105.3175 (/preprints)
2011-05-17, 14:08 [edit]


[1105.2821] Binary black hole mergers in gaseous disks: Simulations in general relativity

Authors: Brian D. Farris, Yuk Tung Liu, Stuart L. Shapiro

Date: 13 May 2011

Abstract: Simultaneous gravitational and electromagnetic wave observations of merging black hole binaries (BHBHs) can provide unique opportunities to study gravitation physics, accretion and cosmology. Here we perform fully general relativistic, hydrodynamic simulations of equal-mass, nonspinning BHBHs coalescing in a circumbinary disk. We evolve the metric using the Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation of Einstein's field equations with standard moving puncture gauge conditions. We handle the hydrodynamics via a high-resolution shock-capturing (HRSC) scheme. We track the inspiral starting from a binary separation of 10M, where M is the total binary mass. We take the disks to have an inner radius at R_iñ15M to account for the hollow created by the binary torques. Our disks extend to R=65M and have an initial scale height of H/R=0.03-0.11. The gas is governed by a Gamma-law EOS, with Gamma equal to 5/3, 4/3, and 1.1. Disks are allowed to relax in the "early inspiral" epoch to provide quasistationary realistic initial data. We then evolve the metric and matter during the "late inspiral and merger" epoch. The later simulations are designed to track BHBH inspiral following disk-binary decoupling, through merger and ringdown, terminating before viscosity has time to fill the hollow about the remnant. We compute the gas flow and accretion rate and estimate the electromagnetic luminosity due to bremsstrahlung and synchrotron emission as a perturbation for optically thin disks. The synchrotron component of the luminosity peaks in the infrared band and should be detectable by WFIRST and possibly the LSST for a 10ˆ8 M_sun binary embedded in a disk with a density ñ10ˆ12/cmˆ3 at z=1, beginning with a maximum value of $L~10ˆ46 n_12ˆ2 M_8ˆ3 erg/s at decoupling, and decreasing steadily over a timescale of ~100 M_8 hours to a value of L~10ˆ45 n_12ˆ2 M_8ˆ3 erg/s at merger.

abs pdf

May 17, 2011

1105.2821 (/preprints)
2011-05-17, 14:07 [edit]


[1105.2825] Radiative efficiency and thermal spectrum of accretion onto Schwarzschild black holes

Authors: Scott C. Noble (Rochester Institute of Technology), Julian H. Krolik (Johns Hopkins University), Jeremy D. Schnittman (NASA/Goddard Space Flight Center), John F. Hawley (University of Virginia)

Date: 13 May 2011

Abstract: Recent general relativistic magneto-hydrodynamic (MHD) simulations of accretion onto black holes have shown that, contrary to the basic assumptions of the Novikov-Thorne model, there can be substantial magnetic stress throughout the plunging region. Additional dissipation and radiation can therefore be expected. We use data from a particularly well-resolved simulation of accretion onto a non-spinning black hole to compute both the radiative efficiency of such a flow and its spectrum if all emitted light is radiated with a thermal spectrum whose temperature matches the local effective temperature. This disk is geometrically thin enough (H/r ~= 0.06) that little heat is retained in the flow. In terms of light reaching infinity (i.e., after allowance for all relativistic effects and for photon capture by the black hole), we find that the radiative efficiency is at least ~=6-10% greater than predicted by the Novikov-Thorne model (complete radiation of all heat might yield another ~6%). We also find that the spectrum more closely resembles the Novikov-Thorne prediction for a/M ~= 0.2--0.3 than for the correct value, a/M=0. As a result, if the spin of a non-spinning black hole is inferred by model-fitting to a Novikov-Thorne model with known black hole mass, distance, and inclination, the inferred a/M is too large by ~= 0.2--0.3.

abs pdf

May 17, 2011

1105.2825 (/preprints)
2011-05-17, 14:07 [edit]


[1105.0009] Revisiting the double-binary-pulsar probe of non-dynamical Chern-Simons gravity

Authors: Yacine Ali-Haïmoud

Date: 29 Apr 2011

Abstract: One of the popular modifications to the theory of general relativity is non-dynamical Chern-Simons (CS) gravity, in which the metric is coupled to an externally prescribed scalar field. Setting accurate constraints to the parameters of the theory is important owing to their implications for the scalar field and/or the underlying fundamental theory. The current best constraints rely on measurements of the periastron precession rate in the double-binary-pulsar system and place a very tight bound on the characteristic CS lengthscale k_csˆ{-1} <~ 3*10ˆ{-9} km. This paper considers several effects that were not accounted for when deriving this bound and lead to a substantial suppression of the predicted rate of periastron precession. It is shown, in particular, that the point mass approximation for extended test bodies does not apply in this case. The constraint to the characteristic CS lengthscale is revised to k_csˆ{-1} <~ 0.4 km, eight orders of magnitude weaker than what was previously found.

abs pdf

May 17, 2011

1105.0009 (/preprints)
2011-05-17, 09:06 [edit]


[1105.1992] An upper limit to the secular variation of the gravitational constant from white dwarf stars

Authors: Enrique Garc&#xed;a-Berro, Pablo Lor&#xe9;n-Aguilar, Santiago Torres, Leandro G. Althaus, Jordi Isern

Date: 10 May 2011

Abstract: A variation of the gravitational constant over cosmological ages modifies the main sequence lifetimes and white dwarf cooling ages. Using an state-of-the-art stellar evolutionary code we compute the effects of a secularly varying G on the main sequence ages and, employing white dwarf cooling ages computed taking into account the effects of a running G, we place constraints on the rate of variation of Newton's constant. This is done using the white dwarf luminosity function and the distance of the well studied open Galactic cluster NGC 6791. We derive an upper bound G'/G ~ -1.8 10ˆ{-12} 1/yr. This upper limit for the secular variation of the gravitational constant compares favorably with those obtained using other stellar evolutionary properties, and can be easily improved if deep images of the cluster allow to obtain an improved white dwarf luminosity function.

abs pdf

May 17, 2011

1105.1992 (/preprints)
2011-05-17, 09:06 [edit]


[1105.0368] Gravitational waves and nonaxisymmetric oscillation modes in mergers of compact object binaries

Authors: Nikolaos Stergioulas, Andreas Bauswein, Kimon Zagkouris, Hans-Thomas Janka

Date: 2 May 2011

Abstract: We study the excitation of nonaxisymmetric modes in the post-merger phase of binary compact object mergers and the associated gravitational wave emission. Our analysis is based on general-relativistic simulations, in the spatial conformal flatness approximation, using smoothed-particle-hydrodynamics for the evolution of matter, and we use a set of equal and unequal mass models, described by two nonzero-temperature hadronic equations of state and by one strange star equation of state. Through Fourier transforms of the evolution of matter variables, we can identify a number of oscillation modes, as well as several nonlinear components (combination frequencies). We focus on the dominant m=2 mode, which forms a triplet with two nonlinear components that are the result of coupling to the quasiradial mode. A corresponding triplet of frequencies is identified in the gravitational wave spectrum, when the individual masses of the compact objects are in the most likely range of 1.2 to 1.35 $M_\odot$. We can thus associate, through direct analysis of the dynamics of the fluid, a specific frequency peak in the gravitational wave spectrum with the nonlinear component resulting from the difference between the m=2 mode and the quasiradial mode. Once such observations become available, both the m=2 and quasiradial mode frequencies could be extracted, allowing for the application of gravitational-wave asteroseismology to the post-merger remnant and leading to tight constraints on the equation of state of high-density matter.

abs pdf

May 06, 2011

1105.0368 (/preprints)
2011-05-06, 22:21 [edit]


[1105.0109] Studying null and time-like geodesics in the classroom

Authors: Thomas M&#xfc;ller, J&#xf6;rg Frauendiener

Date: 30 Apr 2011

Abstract: In a first course of general relativity it is usually quite difficult for students to grasp the concept of a geodesic. It is supposed to be straight (auto-parallel) and yet it 'looks' curved. In these situations it is very useful to have some explicit examples available which show the different behaviour of geodesics. In this paper we present the GeodesicViewer, an interactive tool for studying the behaviour of geodesics in many different space-times. The geodesics can be represented in several ways, depending on the space-time in question. The use of a local reference frame and 'Cartesian-like' coordinates helps the students to develop some intuition in various situations. We present the various features of the GeodesicViewer in the form of readily formulated exercises for the students.

abs pdf

May 06, 2011

1105.0109 (/preprints)
2011-05-06, 22:19 [edit]


[1105.0670] Massive black hole binary eccentricity in rotating stellar systems

Authors: Alberto Sesana, Alessia Gualandris, Massimo Dotti

Date: 3 May 2011

Abstract: In this letter we study the eccentricity evolution of a massive black hole (MBH) binary (MBHB) embedded in a rotating stellar cusp. Following the observation that stars on counter-rotating (with respect to the MBHB) orbits extract angular momentum from the binary more efficiently then their co-rotating counterparts, the eccentricity evolution of the MBHB must depend on the degree of co-rotation (counter-rotation) of the surrounding stellar distribution. Using an hybrid scheme that couples numerical three-body scatterings to an analytical formalism for the cusp-binary interaction, we verify this hypothesis by evolving the MBHB in spherically symmetric cusps with different fractions F of co-rotating stars. Consistently with previous works, binaries in isotropic cusps (F=0.5) tend to increase their eccentricity, and when F approaches zero (counter-rotating cusps) the eccentricity rapidly increases to almost unity. Conversely, binaries in cusps with a significant degree of co-rotation (F>0.7) tend to become less and less eccentric, circularising quite quickly for F approaching unity. Direct N-body integrations performed to test the theory, corroborate the results of the hybrid scheme, at least at a qualitative level. We discuss quantitative differences, ascribing their origin to the oversimplified nature of the hybrid approach.

abs pdf

May 06, 2011

1105.0670 (/preprints)
2011-05-06, 22:18 [edit]


[1105.0918] Galactic-center S-Stars as a prospective test of the Einstein Equivalence Principle

Authors: R. Angelil, P. Saha

Date: 4 May 2011

Abstract: The S-Stars in the Galactic-center region are found to be on near-perfect Keplerian orbits around presumably a supermassive black hole, with periods of 15-50 yr. Since these stars reach a few percent of light speed at pericenter, various relativistic effects are expected, and have been discussed in the literature. We argue that an elegant test of the Einstein equivalence principle should be possible with existing instruments, through spectroscopic monitoring of an S-star concentrated during the months around pericenter, supplemented with an already-adequate astrometric determination of the inclination. In essence, the spectrum of an S-star can be considered a heterogeneous ensemble of clocks in a freely-falling frame, which near pericenter is moving at relativistic speeds.

abs pdf

May 06, 2011

1105.0918 (/preprints)
2011-05-06, 22:17 [edit]


[1104.5552] Toward an optimal search strategy of optical and gravitational wave emissions from binary neutron star coalescence

Authors: D.M. Coward, B. Gendre, P.J. Sutton, E.J. Howell, T. Regimbau, M. Laas-Bourez, A. Klotz, M. Boer, M. Branchesi

Date: 29 Apr 2011

Abstract: Observations of an optical source coincident with gravitational wave emission detected from a binary neutron star coalescence will improve the confidence of detection, provide host galaxy localisation, and test models for the progenitors of short gamma ray bursts. We employ optical observations of three short gamma ray bursts, 050724, 050709, 051221, to estimate the detection rate of a coordinated optical and gravitational wave search of neutron star mergers. Model R-band optical afterglow light curves of these bursts that include a jet-break are extrapolated for these sources at the sensitivity horizon of an Advanced LIGO/Virgo network. Using optical sensitivity limits of three telescopes, namely TAROT (m=18), Zadko (m=21) and an (8-10) meter class telescope (m=26), we approximate detection rates and cadence times for imaging. We find a median coincident detection rate of 4 yrˆ{-1} for the three bursts. GRB 050724 like bursts, with wide opening jet angles, offer the most optimistic rate of 13 coincident detections yrˆ{-1}, and would be detectable by Zadko up to five days after the trigger. Late time imaging to m=26 could detect off-axis afterglows for GRB 051221 like bursts several months after the trigger. For a broad distribution of beaming angles, the optimal strategy for identifying the optical emissions triggered by gravitational wave detectors is rapid response searches with robotic telescopes followed by deeper imaging at later times if an afterglow is not detected within several days of the trigger.

abs pdf

May 02, 2011

1104.5552 (/preprints)
2011-05-02, 13:57 [edit]


[1104.5650] Sky localization of complete inspiral-merger-ringdown signals for nonspinning massive black hole binaries

Authors: Sean T. McWilliams, Ryan N. Lang, John G. Baker, James Ira Thorpe

Date: 29 Apr 2011

Abstract: We investigate the capability of LISA to measure the sky position of equal-mass, nonspinning black hole binaries, combining for the first time the entire inspiral-merger-ringdown signal, the effect of the LISA orbits, and the complete three-channel LISA response. We consider an ensemble of systems near the peak of LISA's sensitivity band, with total rest mass of 2\times10ˆ6 M\odot, a redshift of z = 1, and randomly chosen orientations and sky positions. We find median sky localization errors of approximately \sim3 arcminutes. This is comparable to the field of view of powerful electromagnetic telescopes, such as the James Webb Space Telescope, that could be used to search for electromagnetic signals associated with merging massive black holes. We investigate the way in which parameter errors decrease with measurement time, focusing specifically on the additional information provided during the merger-ringdown segment of the signal. We find that this information improves all parameter estimates directly, rather than through diminishing correlations with any subset of well- determined parameters. Although we have employed the baseline LISA design for this study, many of our conclusions regarding the information provided by mergers will be applicable to alternative mission designs as well.

abs pdf

May 02, 2011

1104.5650 (/preprints)
2011-05-02, 13:56 [edit]


[1104.5615] Gravitational radiation for extreme mass ratio inspirals to the 14th post-Newtonian order

Authors: Ryuichi Fujita

Date: 29 Apr 2011

Abstract: We derive gravitational waveforms needed to compute the 14th post-Newtonian (14PN) order energy flux, i.e. $vˆ{28}$ beyond Newtonian approximation where $v$ is the orbital velocity of a test particle, in a circular orbit around a Schwarzschild black hole. We exhibit clearly the convergence of the energy flux in the PN expansion and suggest the fitting formula which can be used for more general case. The phase difference between the 14PN waveforms and numerical waveforms after two years inspiral becomes about $10ˆ{-7}$ for $\mu/M=10ˆ{-4}$ and $10ˆ{-3}$ for $\mu/M=10ˆ{-5}$ where $\mu$ and $M$ are the masses of a compact object and a supermassive black hole at the centers of galaxies respectively. The 14PN expressions will lead to the parameter estimation comparable to numerical waveforms for extreme mass ratio inspirals, which are one of the main targets of Laser Interferometer Space Antenna.

abs pdf

May 02, 2011

1104.5615 (/preprints)
2011-05-02, 13:56 [edit]


[1104.5659] Tail-induced spin-orbit effect in the gravitational radiation of compact binaries

Authors: Luc Blanchet (IAP), Alessandra Buonanno, Guillaume Faye (IAP)

Date: 29 Apr 2011

Abstract: Gravitational waves contain tail effects which are due to the back-scattering of linear waves in the curved space-time geometry around the source. In this paper we improve the knowledge and accuracy of the two-body inspiraling post-Newtonian (PN) dynamics and gravitational-wave signal by computing the spin-orbit terms induced by tail effects. Notably, we derive those terms at 3PN order in the gravitational-wave energy flux, and 2.5PN and 3PN orders in the wave polarizations. This is then used to derive the spin-orbit tail effects in the phasing through 3PN order. Our results can be employed to carry out more accurate comparisons with numerical-relativity simulations and to improve the accuracy of analytical templates aimed at describing the all process of inspiral, merger and ringdown.

abs pdf

May 02, 2011

1104.5659 (/preprints)
2011-05-02, 13:55 [edit]


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