[astro-ph/0605624] On the search of electromagnetic cosmological counterparts to coalescences of massive black hole binaries

Authors: M. Dotti, R. Salvaterra, A. Sesana, M. Colpi, F. Haardt

Date: Wed, 24 May 2006

Abstract: We explore the nature of possible electromagnetic counterparts of coalescences of massive black hole binaries at cosmological distances detectable by the Laser Interferometer Space Antenna (LISA). An electromagnetic precursor, during the last year of gravitational wave (GW)-driven inspiral, or an afterglow within few years after coalescence, may highlight the position in the sky of galaxies hosting LISA sources. We show that observations of precursors and afterglows are mutually exclusive, depending on the mass of the primary black hole. Precursors are expected to occur in binaries where the primary (more massive) black hole is heavier than ~10ˆ7 \Msun. They may correspond to on-off states of accretion, i.e., to a bright X-ray source decaying into quiescence before black hole coalescence, and are likely associated to disturbed galaxies showing signs of ongoing starbursts. Coalescences of lighter binaries, with masses <5x10ˆ6 \Msun, lack of any precursor, as gas is expected to be consumed long before the GW-driven orbital decay. Such events would not be hosted by (massive) galaxies with an associated starburst, given the slow binary inspiral time compared to the typical time scale of starbursts. By contrast, coalescence, for such light binaries, is followed by an electromagnetic afterglow, i.e., an off-on accretion state rising in <20 yrs. Using a cosmological merger tree algorithm, we show that future X-ray missions such as XEUS will be able to identify, in 20 yrs operation, almost all the massive BH binary detectable by LISA, and, in only 5 yrs, all the LISA sources at z>6.

abs pdf

May 30, 2006

0605624 (/preprints/astro-ph)
2006-05-30, 10:28 [edit]

[gr-qc/0605140] Higher-order spin effects in the dynamics of compact binaries II. Radiation field

Authors: Luc Blanchet (IAP), Alessandra Buonanno (IAP, Department of Physics, University of Maryland, Apc), Guillaume Faye (IAP)

Date: Sat, 27 May 2006

Abstract: Motivated by the search for gravitational waves emitted by binary black holes, we investigate the gravitational radiation field of point particles with spins within the framework of the multipolar-post-Newtonian wave generation formalism. We compute: (i) the spin-orbit (SO) coupling effects in the binary's mass and current quadrupole moments one post-Newtonian (1PN) order beyond the dominant effect, (ii) the SO contributions in the gravitational-wave energy flux and (iii) the secular evolution of the binary's orbital phase up to 2.5PN order. Crucial ingredients for obtaining the 2.5PN contribution in the orbital phase are the binary's energy and the spin precession equations, derived in paper I of this series. These results provide more accurate gravitational-wave templates to be used in the data analysis of rapidly rotating Kerr-type black-hole binaries with the ground-based detectors LIGO, Virgo, GEO 600 and TAMA300, and the space-based detector LISA.

abs pdf

May 30, 2006

0605140 (/preprints/gr-qc)
2006-05-30, 09:13 [edit]

[gr-qc/0605139] Higher-order spin effects in the dynamics of compact binaries I. Equations of motion

Authors: Guillaume Faye (IAP), Luc Blanchet (IAP), Alessandra Buonanno (IAP, Department of Physics, University of Maryland, Apc)

Date: Sat, 27 May 2006

Abstract: We derive the equations of motion of spinning compact binaries including the spin-orbit (SO) coupling terms one post-Newtonian (PN) order beyond the leading-order effect. For black holes maximally spinning this corresponds to 2.5PN order. Our result for the equations of motion essentially confirms the previous result by Tagoshi, Ohashi and Owen. We also compute the spin-orbit effects up to 2.5PN order in the conserved (Noetherian) integrals of motion, namely the energy, the total angular momentum, the linear momentum and the center-of-mass integral. We obtain the spin precession equations at 1PN order beyond the leading term, as well. Those results will be used in a future paper to derive the time evolution of the binary orbital phase, providing more accurate templates for LIGO-Virgo-LISA type interferometric detectors.

abs pdf

May 30, 2006

0605139 (/preprints/gr-qc)
2006-05-30, 09:12 [edit]

[gr-qc/0605135] New ways to catch a wave

Authors: Neil J. Cornish, Edward K. Porter

Date: Fri, 26 May 2006

Abstract: The gravitational wave signals from coalescing Supermassive Black Hole Binaries are one of the prime targets for the Laser Interferometer Space Antenna (LISA). With optimal data processing techniques the LISA observatory should be able to detect these black hole mergers anywhere in the Universe. The challenge is to find ways to dig the signals out of a combination of instrument noise and the large foreground from stellar mass binaries in our own galaxy. The standard procedure of matched filtering against a bank of templates can be computationally prohibitive, especially when the black holes are spinning or the mass ratio is large. Here we develop an alternative approach based on annealed Markov Chains that is orders of magnitude cheaper than a grid search. We demonstrate our approach on a simulated LISA data stream that contains the signal from a binary system of Schwarzschild Black Holes, embedded in instrument noise and a foreground containing 26 million galactic binaries. The annealed chains are able to accurately recover the 9 parameters that describe the black hole binary without first having to remove any of the bright sources in the foreground.

abs pdf

May 29, 2006

0605135 (/preprints/gr-qc)
2006-05-29, 15:16 [edit]

[gr-qc/0605118] Quasinormal ringing of Kerr black holes. I. The excitation factors

Authors: Emanuele Berti, Vitor Cardoso

Date: Sun, 21 May 2006

Abstract: Distorted black holes radiate gravitational waves. In the so-called ringdown phase radiation is emitted in a discrete set of complex quasinormal frequencies, whose values depend only on the black hole's mass and angular momentum. Ringdown radiation could be detectable with large signal-to-noise ratio by the Laser Interferometer Space Antenna LISA. If more than one mode is detected, tests of the black hole nature of the source become possible. The detectability of different modes depends on their relative excitation, which in turn depends on the cause of the perturbation (i.e. on the initial data). A ‘universal’, initial data-independent measure of the relative mode excitation is encoded in the poles of the Green's function that propagates small perturbations of the geometry (‘excitation factors’). We compute for the first time the excitation factors for general-spin perturbations of Kerr black holes. We find that for corotating modes with $l=m$ the excitation factors tend to zero in the extremal limit, and that the contribution of the overtones should be more significant when the black hole is fast rotating. We also present the first analytical calculation of the large-damping asymptotics of the excitation factors for static black holes, including the Schwarzschild and Reissner-Nordstrom metrics. This is an important step to determine the convergence properties of the quasinormal mode expansion.

abs pdf

May 22, 2006

0605118 (/preprints/gr-qc)
2006-05-22, 20:45 [edit]

[gr-qc/0605101] Supermassive black holes or boson stars? Hair counting with gravitational wave detectors

Authors: Emanuele Berti, Vitor Cardoso

Date: Wed, 17 May 2006

Abstract: The evidence for supermassive Kerr black holes in galactic centers is strong and growing, but only the detection of gravitational waves will convincingly rule out other possibilities to explain the observations. The Kerr spacetime is completely specified by the first two multipole moments: mass and angular momentum. This is usually referred to as the ‘no-hair theorem’, but it is really a ‘two-hair’ theorem. If general relativity is the correct theory of gravity, the most plausible alternative to a supermassive Kerr black hole is a rotating boson star. Numerical calculations indicate that the spacetime of rotating boson stars is determined by the first three multipole moments (‘three-hair theorem’). LISA could accurately measure the oscillation frequencies of these supermassive objects. We propose to use these measurements to ‘count their hair’, unambiguously determining their nature and properties.

abs pdf

May 17, 2006

0605101 (/preprints/gr-qc)
2006-05-17, 18:34 [edit]

[gr-qc/0605085] MCMC Exploration of Supermassive Black Hole Binary Inspirals

Authors: Neil J. Cornish, Edward K. Porter

Date: Mon, 15 May 2006

Abstract: The Laser Interferometer Space Antenna will be able to detect the inspiral and merger of Super Massive Black Hole Binaries (SMBHBs) anywhere in the Universe. Standard matched filtering techniques can be used to detect and characterize these systems. Markov Chain Monte Carlo (MCMC) methods are ideally suited to this and other LISA data analysis problems as they combine the ability to rapidly search large dimension parameter spaces with the ability to provide error estimates for the recovered parameters. Here we compare the posterior parameter distributions derived by an MCMC algorithm with the distributions predicted by the Fisher information matrix. We find excellent agreement for the extrinsic parameters, and a systematic over estimate of the errors in the intrinsic parameters.

abs pdf

May 15, 2006

0605085 (/preprints/gr-qc)
2006-05-15, 17:46 [edit]

[gr-qc/0605071] A Markov Chain Monte Carlo approach to the study of massive black hole binary systems with LISA

Authors: E.D.L.Wickham, A.Stroeer, A.Vecchio

Date: Thu, 11 May 2006

Abstract: The Laser Interferometer Space Antenna (LISA) will produce a data stream containing a vast number of overlapping sources: from strong signals generated by the coalescence of massive black hole binary systems to much weaker radiation form sub-stellar mass compact binaries and extreme-mass ratio inspirals. It has been argued that the observation of weak signals could be hampered by the presence of loud ones and that they first need to be removed to allow such observations. Here we consider a different approach in which sources are studied simultaneously within the framework of Bayesian inference. We investigate the simplified case in which the LISA data stream contains radiation from a massive black hole binary system superimposed over a (weaker) quasi-monochromatic waveform generated by a white dwarf binary. We derive the posterior probability density function of the model parameters using an automatic Reversible Jump Markov Chain Monte Carlo algorithm (RJMCMC). We show that the information about the sources and noise are retrieved at the expected level of accuracy without the need of removing the stronger signal. Our analysis suggests that this approach is worth pursuing further and should be considered for the actual analysis of the LISA data.

abs pdf

May 12, 2006

0605071 (/preprints/gr-qc)
2006-05-12, 09:27 [edit]

[astro-ph/0605227] The LISA verification binaries

Authors: A. Stroeer, A. Vecchio

Date: Tue, 9 May 2006

Abstract: The Laser Interferometer Space Antenna (LISA) guarantees the detection of gravitational waves by monitoring a handful of known nearby galactic binary systems, the so-called ‘verification binaries’. We consider the most updated information on the source parameters for the thirty more promising verification binaries. We investigate which of them are indeed guaranteed sources for LISA and estimate the accuracy of the additional information that can be extracted during the mission. Our analysis considers the two independent Michelson outputs that can be synthesised from the LISA constellation, and we model the LISA transfer function using the rigid adiabatic approximation. We carry out extensive Monte Carlo simulations to explore the dependency of our results on unknown or poorly constrained source parameters. We find that four sources -- RXJ0806.3+1527, V407 Vul, ES Cet and AM CVn -- are clearly detectable in one year of observation; RXJ0806.3+1527 should actually be observable in less than a week. For these sources LISA will also provide information on yet unknown parameters with an error between approximately 1 percent and 10 percent. Four additional binary systems -- HP Lib, 4U 1820-30, WZ Sge and KPD 1930+2752 -- might also be marginally detectable.

abs pdf

May 10, 2006

0605227 (/preprints/astro-ph)
2006-05-10, 20:35 [edit]

[gr-qc/0605021] Parameter estimation of coalescing supermassive black hole binaries with LISA

Authors: K G Arun

Date: Wed, 3 May 2006

Abstract: Laser Interferometer Space Antenna (LISA) will routinely observe coalescences of supermassive black hole (BH) binaries up to very high redshifts. LISA can measure mass parameters of such coalescences to a relative accuracy of $10ˆ{-4}-10ˆ{-6}$, for sources at a distance of 3 Gpc. The problem of parameter estimation of massive nonspinning binary black holes using post-Newtonian (PN) phasing formula is studied in the context of LISA. Specifically, the performance of the 3.5PN templates is compared against its 2PN counterpart. The estimation of the mass parameters ${\cal M}$ and $\eta$ are significantly enhanced by using the 3.5PN waveform instead of the 2PN one. The estimation of angular resolution and distance show very little improvement. For an equal mass binary of $2\times10ˆ6M_\odot$ at a luminosity distance of 3 Gpc, the improvement in chirp mass is $\sim 8%$ and that of $\eta$ is $\sim 40%$. Estimation of coalescence time $t_c$ shows negligible variation with PN orders. The improvement is larger for the unequal mass binary mergers. The parameter estimation using a single detector of LISA is compared against the case where LISA is considered to be a two detector network. The two detector configuration measures parameters with enhanced accuracy. (Abridged)

abs pdf

May 04, 2006

0605021 (/preprints/gr-qc)
2006-05-04, 08:35 [edit]

[astro-ph/0605034] Parameter estimation of binary compact objects with LISA: Effects of time-delay interferometry, Doppler modulation, and frequency evolution

Authors: Aaron Rogan, Sukanta Bose (Washington State University)

Date: Mon, 1 May 2006

Abstract: We study the limits on how accurately LISA will be able to estimate the parameters of low-mass compact binaries, comprising white dwarfs (WDs), neutron stars (NSs) or black holes (BHs), while battling the amplitude, frequency, and phase modulations of their signals. We show that Doppler-phase modulation aids sky-position resolution in every direction, improving it especially for sources near the poles of the ecliptic coordinate system. However, it increases the frequency estimation error by a factor of over 1.5 at any sky position, and at f=3 mHz. Since accounting for Doppler-phase modulation is absolutely essential at all LISA frequencies and for all chirp masses in order to avoid a fractional loss of signal-to-noise ratio (SNR) of more than 30%, LISA science will be simultaneously aided and limited by it. For a source with f > 2.5mHz, searching for its frequency evolution for 1 year worsens the error in the frequency estimation by a factor of over 3.5 relative to that of sources with f < 1mHz. Increasing the integration time to 2 years reduces this relative error factor to about 2, which still adversely affects the resolvability of the galactic binary confusion noise. Thus, unless the mission lifetime is increased several folds, the only other recourse available for reducing the errors is to exclude the chirp parameter from ones search templates. Doing so improves the SNR-normalized parameter estimates. This works for the lightest binaries since their SNR itself does not suffer from that exclusion. However, for binaries involving a neutron star, a black hole, or both, the SNR and, therefore, the parameter estimation, can take a significant hit, thus, severely affecting the ability to resolve such members in LISA's confusion noise.

abs pdf

May 02, 2006

0605034 (/preprints/astro-ph)
2006-05-02, 21:13 [edit]

[gr-qc/0605002] Coherent network analysis technique for discriminating gravitational-wave bursts from instrumental noise

Authors: Shourov Chatterji, Albert Lazzarini, Leo Stein, Patrick Sutton, Antony Searle, Massimo Tinto

Date: Mon, 1 May 2006

Abstract: Existing coherent network analysis techniques for detecting gravitational-wave bursts simultaneously test data from multiple observatories for consistency with the expected properties of the signals. These techniques assume the output of the detector network to be the sum of a stationary Gaussian noise process and a gravitational-wave signal, and they may fail in the presence of transient non-stationarities, which are common in real detectors. In order to address this problem we introduce a consistency test that is robust against noise non-stationarities and allows one to distinguish between gravitational-wave bursts and noise transients. This technique does not require any a priori knowledge of the putative burst waveform.

abs pdf

May 02, 2006

0605002 (/preprints/gr-qc)
2006-05-02, 09:01 [edit]

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