[gr-qc/0506116] Detecting extreme mass ratio inspirals with LISA using time-frequency methods II: search characterization

Authors: Jonathan Gair, Linqing Wen

Date: Thu, 23 Jun 2005

Abstract: The inspirals of stellar-mass compact objects into supermassive black holes constitute some of the most important sources for LISA. Detection of these sources using fully coherent matched filtering is computationally intractable, so alternative approaches are required. In a previous paper (Wen and Gair 2005, gr-qc/0502100), we outlined a detection method based on looking for excess power in a time-frequency spectrogram of the LISA data. The performance of the algorithm was assessed using a single ‘typical’ trial waveform and approximations to the noise statistics. In this paper we present results of Monte Carlo simulations of the search noise statistics and examine its performance in detecting a wider range of trial waveforms. We show that typical extreme mass ratio inspirals (EMRIs) can be detected at distances of up to 1--3 Gpc, depending on the source parameters. We also discuss some remaining issues with the technique and possible ways in which the algorithm can be improved.

abs pdf

Jun 24, 2005

0506116 (/preprints/gr-qc)
2005-06-24, 14:40 [edit]


An Introduction to Signal Extraction in LIGO

Eric D. Black and Ryan N. Gutenkunst, An Introduction to Signal Extraction in Interferometric Gravitational-Wave Detectors, Am. J. Phys.

link

Jun 22, 2005

gutenkunst (/preprints)
2005-06-22, 19:40 [edit]


[astro-ph/0505545] Gravitational Wave Astrometry for Rapidly Rotating Neutron Stars and Estimation of Their Distances

Authors: Naoki Seto (Caltech)

Date: Thu, 26 May 2005

Abstract: We discuss an astrometric timing effect on data analysis of continuous gravitational waves from rapidly rotating isolated neutron stars. Special attention is directed to the possibility of determining their distances by measuring the curvature of the wave fronts. We predict that if continuous gravitational waves from an unknown neutron star with a stable rotation are detected around 1kHz within 1/3yr by initial LIGO detectors and the ellipticity parameter epsilon is smaller than 10ˆ{-6}, the distance r to the source can be estimated with relative error \Delta r/r of \sim 10% by using the broad band configuration of advanced LIGO detectors over 3 years. By combining the observed amplitude of the waves with the estimated distance, information on the parameter $\epsilon$ can be obtained purely through gravitational wave measurements.

abs pdf

Jun 19, 2005

0505545 (/preprints/astro-ph)
2005-06-19, 20:57 [edit]


[gr-qc/0506083] Gravitational Waves from Compact Sources

Authors: Kostas D. Kokkotas, Nikolaos Stergioulas

Date: Wed, 15 Jun 2005

Abstract: We review sources of high-frequency gravitational waves, summarizing our current understanding of emission mechanisms, expected amplitudes and event rates. The most promising sources are gravitational collapse (formation of black holes or neutron stars) and subsequent ringing of the compact star, secular or dynamical rotational instabilities and high-mass compact objects formed through the merger of binary neutron stars. Significant and unique information for the various stages of the collapse, the structure of protoneutron stars and the high density equation of state of compact objects can be drawn from careful study of gravitational wave signals.

abs pdf

Jun 16, 2005

0506083 (/preprints/gr-qc)
2005-06-16, 09:21 [edit]


[gr-qc/0506078] Black Holes in Astrophysics

Authors: Ramesh Narayan

Date: Tue, 14 Jun 2005

Abstract: This article reviews the current status of black hole astrophysics, focusing on topics of interest to a physics audience. Astronomers have discovered dozens of compact objects with masses greater than 3 solar masses, the likely maximum mass of a neutron star. These objects are identified as black hole candidates. Some of the candidates have masses of 5 to 20 solar masses and are found in X-ray binaries, while the rest have masses from a million to a billion solar masses and are found in galactic nuclei. A variety of methods are being tried to estimate the spin parameters of the candidate black holes. There is strong circumstantial evidence that many of the objects have event horizons. Recent MHD simulations of magnetized plasma accreting on rotating black holes seem to hint that relativistic jets may be produced by a magnetic analog of the Penrose process.

abs pdf

Jun 15, 2005

0506078 (/preprints/gr-qc)
2005-06-15, 14:54 [edit]


[astro-ph/0506181] Gravitational waves from remnants of ultraluminous X-ray sources

Authors: Clovis Hopman (Weizmann), Simon Portegies Zwart (UvA)

Date: Wed, 8 Jun 2005

Abstract: Ultraluminous X-ray sources (ULXs) with X-ray luminosities larger than the Eddington luminosity of stellar mass objects may be powered by intermediate mass black holes (IBHs) of masses Mbh~10ˆ3Msun. If IBHs form in young dense stellar clusters, they can be fed by Roche lobe overflow from a tidally captured massive (Ms>10Msun) stellar companion. After the donor leaves the main sequence it forms a compact remnant, which spirals in due to gravitational wave (GW) emission. We show that space based detectors such as the Light Interferometer Space Antenna are likely to detect several of these sources. GW sources stemming from this scenario have small eccentricities which give distinct GW signals. Detection of such a GW signal will unambiguously prove the existence of IBHs, and support the hypothesis that some ULXs are powered by IBHs with captured companions.

abs pdf

Jun 15, 2005

0506181 (/preprints/astro-ph)
2005-06-15, 14:54 [edit]


[gr-qc/0506058] Expected Coalescence Rate of Double Neutron Stars for Ground Based Interferometer

Authors: T. Regimbau, J.A. de Freitas Pacheco, A. Spallicci, S. Vincent

Date: Thu, 9 Jun 2005

Abstract: In this paper we present new estimates of the coalescence rate of neutron star binaries in the local universe and we discuss its consequences for the first generations of ground based interferometers. Our approach based on both evolutionary and statistical methods gives a galactic merging rate of 1.7 10$ˆ{-5}$ yr$ˆ{-1}$, in the range of previous estimates 10$ˆ{-6}$ - 10$ˆ{-4}$ yr$ˆ{-1}$. The local rate which includes the contribution of elliptical galaxies is two times higher, in the order of 3.4 10$ˆ{-5}$ yr$ˆ{-1}$. We predict one detection every 148 and 125 years with initial VIRGO and LIGO, and up to 6 events per year with their advanced configuration. Our recent detection rate estimates from investigations on VIRGO future improvements are quoted.

abs pdf

Jun 13, 2005

0506058 (/preprints/gr-qc)
2005-06-13, 10:39 [edit]


[gr-qc/0506059] LISA Data Analysis using MCMC methods

Authors: Neil J. Cornish, Jeff Crowder

Date: Fri, 10 Jun 2005

Abstract: The Laser Interferometer Space Antenna (LISA) is expected to simultaneously detect many thousands of low frequency gravitational wave signals. This presents a data analysis challenge that is very different to the one encountered in ground based gravitational wave astronomy. LISA data analysis requires the identification of individual signals from a data stream containing an unknown number of overlapping signals. Because of the signal overlaps, a global fit to all the signals has to be performed in order to avoid biasing the solution. However, performing such a global fit requires the exploration of an enormous parameter space with a dimension upwards of 50,000. Markov Chain Monte Carlo (MCMC) methods offer a very promising solution to the LISA data analysis problem. MCMC algorithms are able to efficiently explore large parameter spaces, simultaneously providing parameter estimates, error analyses and even model selection. Here we present the first application of MCMC methods to simulated LISA data and demonstrate the great potential of the MCMC approach. Our implementation uses a generalized F-statistic to evaluate the likelihoods, and simulated annealing to speed convergence of the Markov chains. As a final step we super-cool the chains to extract maximum likelihood estimates, and estimates of the Bayes factors for competing models. We find that the MCMC approach is able to correctly identify the number of signals present, extract the source parameters, and return error estimates consistent with Fisher information matrix predictions.

abs pdf

Jun 13, 2005

0506059 (/preprints/gr-qc)
2005-06-13, 10:39 [edit]


[gr-qc/0506055] Bayesian modeling of source confusion in LISA data

Authors: Richard Umstaetter, Nelson Christensen, Martin Hendry, Renate Meyer, Vimal Simha, John Veitch, Sarah Vigeland, Graham Woan

Date: Thu, 9 Jun 2005

Abstract: One of the greatest data analysis challenges for the Laser Interferometer Space Antenna (LISA) is the need to account for a large number of gravitational wave signals from compact binary systems expected to be present in the data. We introduce the basis of a Bayesian method that we believe can address this challenge, and demonstrate its effectiveness on a simplified problem involving one hundred synthetic sinusoidal signals in noise. We use a reversible jump Markov chain Monte Carlo technique to infer simultaneously the number of signals present, the parameters of each identified signal, and the noise level. Our approach therefore tackles the detection and parameter estimation problems simultaneously, without the need to evaluate formal model selection criteria, such as the Akaike Information Criterion or explicit Bayes factors. The method does not require a stopping criterion to determine the number of signals, and produces results which compare very favorably with classical spectral techniques.

abs pdf

Jun 10, 2005

0506055 (/preprints/gr-qc)
2005-06-10, 15:13 [edit]


[astro-ph/0503343] Scattering of Gravitational Waves by the Weak Gravitational Fields of Lens Objects

Authors: Ryuichi Takahashi, Teruaki Suyama, Shugo Michikoshi

Date: Wed, 8 Jun 2005

Abstract: We consider the scattering of the gravitational waves by the weak gravitational fields of lens objects. We obtain the scattered gravitational waveform by treating the gravitational potential of the lens to first order, i.e. using the Born approximation. We find that the effect of scattering on the waveform is roughly given by the Schwarzschild radius of the lens divided by the wavelength of gravitational wave for a compact lens object. If the lenses are smoothly distributed, the effect of scattering is of the order of the convergence field $\kappa$ along the line of sight to the source. In the short wavelength limit, the amplitude is magnified by $1+\kappa$, which is consistent with the result in weak gravitational lensing.

abs pdf

Jun 09, 2005

0503343 (/preprints/astro-ph)
2005-06-09, 14:10 [edit]


[astro-ph/0504294] Gravitational waves, inflation and the cosmic microwave background: towards testing the slow-roll paradigm

Authors: Carlo Ungarelli, Pier Stefano Corasaniti, R.A. Mercer, Alberto Vecchio

Date: Wed, 8 Jun 2005

Abstract: One of the fundamental and yet untested predictions of inflationary models is the generation of a very weak cosmic background of gravitational radiation. We investigate the sensitivity required for a space-based gravitational wave laser interferometer with peak sensitivity at $\sim 1$ Hz to observe such signal as a function of the model parameters and compare it with indirect limits that can be set with data from present and future cosmic microwave background missions. We concentrate on signals predicted by slow-roll single field inflationary models and instrumental configurations such as those proposed for the LISA follow-on mission: Big Bang Observer.

abs pdf

Jun 09, 2005

0504294 (/preprints/astro-ph)
2005-06-09, 14:10 [edit]


[gr-qc/0506047] Resonant growth of stellar oscillations by incident gravitational waves

Authors: Yasufumi Kojima, Hajime Tanimoto

Date: Wed, 8 Jun 2005

Abstract: Stellar oscillation under the combined influences of incident gravitational wave and radiation loss is studied in a simple toy model. The star is approximated as a uniform density ellipsoid in the Newtonian gravity including radiation damping through quadrupole formula. The time evolution of the oscillation is significantly controlled by the incident wave amplitude $h$, frequency $\nu$ and damping time $\tau$. If a combination $ h \nu \tau $ exceeds a threshold value, which depends on the resonance mode, the resonant growth is realized.

abs pdf

Jun 09, 2005

0506047 (/preprints/gr-qc)
2005-06-09, 14:09 [edit]


[gr-qc/0506025] A Data Analysis Technique for the LIGO-ALLEGRO Stochastic Background Search

Authors: John T. Whelan, Sukanta Bose, Jonathan Hanson, Ik Siong Heng, Warren W. Johnson, Martin P. McHugh, Peter Zhang

Date: Sun, 5 Jun 2005

Abstract: We describe the cross-correlation measurements being carried out on data from the LIGO Livingston Observatory and the ALLEGRO resonant bar detector. The LIGO data are sampled at 16384 Hz while the ALLEGRO data are base-banded, i.e., heterodyned at 899 Hz and then sampled at 250 Hz. We handle these different sampling parameters by working in the Fourier domain, and demonstrate the approximate equivalence of this measurement to a hypothetical time-domain method in which both data streams are upsampled.

abs pdf

Jun 07, 2005

0506025 (/preprints/gr-qc)
2005-06-07, 09:24 [edit]


[gr-qc/0506015] Beyond LISA: Exploring Future Gravitational Wave Missions

Authors: Jeff Crowder, Neil J. Cornish

Date: Fri, 3 Jun 2005

Abstract: The Advanced Laser Interferometer Antenna (ALIA) and the Big Bang Observer (BBO) have been proposed as follow on missions to the Laser Interferometer Space Antenna (LISA). Here we study the capabilities of these observatories, and how they relate to the science goals of the missions. We find that the Advanced Laser Interferometer Antenna in Stereo (ALIAS), our proposed extension to the ALIA mission, will go considerably further toward meeting ALIA's main scientific goal of studying intermediate mass black holes. We also compare the capabilities of LISA to a related extension of the LISA mission, the Laser Interferometer Space Antenna in Stereo (LISAS). Additionally, we find that an alternative mission more modest than the BBO is sufficient to address the BBO's key scientific goal of detecting the Gravitational Wave Background, while still providing detailed information about foreground sources.

abs pdf

Jun 06, 2005

0506015 (/preprints/gr-qc)
2005-06-06, 12:05 [edit]


[gr-qc/0506008] Extreme Mass Ratio Binary: Radiation reaction and gravitational waveform

Authors: Yasushi Mino

Date: Wed, 1 Jun 2005

Abstract: For a successful detection of gravitational waves by LISA, it is essential to construct theoretical waveforms in a reliable manner. We discuss gravitational waves from an extreme mass ratio binary system which is expected to be a promising target of the LISA project.
The extreme mass ratio binary is a binary system of a supermassive black hole and a stellar mass compact object. As the supermassive black hole dominates the gravitational field of the system, we suppose that the system might be well approximated by a metric perturbation of a Kerr black hole. We discuss a recent theoretical progress in calculating the waveforms from such a system.

abs pdf

Jun 02, 2005

0506008 (/preprints/gr-qc)
2005-06-02, 12:18 [edit]


[gr-qc/0505156] Tidal coupling of a Schwarzschild black hole and circularly orbiting moon

Authors: Hua Fang, Geoffrey Lovelace

Date: Wed, 1 Jun 2005

Abstract: We describe the possibility of using LISA's gravitational-wave observations to study, with high precision, the response of a massive central body to the tidal gravitational pull of an orbiting, compact, small-mass object. Motivated by this application, we use first-order perturbation theory to study tidal coupling for an idealized case: a massive Schwarzschild black hole, tidally perturbed by a much less massive moon in a distant, circular orbit. We investigate the details of how the tidal deformation of the hole gives rise to an induced quadrupole moment in the hole's external gravitational field at large radii. In the limit that the moon is static, we find, in Schwarzschild coordinates and Regge-Wheeler gauge, the surprising result that there is no induced quadrupole moment. We show that this conclusion is gauge dependent and that the static, induced quadrupole moment for a black hole is inherently ambiguous. For the orbiting moon and the central Schwarzschild hole, we find (in agreement with a recent result of Poisson) a time-varying induced quadrupole moment that is proportional to the time derivative of the moon's tidal field. As a partial analog of a result derived long ago by Hartle for a spinning hole and a stationary distant companion, we show that the orbiting moon's tidal field induces a tidal bulge on the hole's horizon, and that the rate of change of the horizon shape leads the perturbing tidal field at the horizon by a small angle.

abs pdf

Jun 01, 2005

0505156 (/preprints/gr-qc)
2005-06-01, 09:34 [edit]


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