522 research outputs found
The Mock LISA Data Challenges: from challenge 3 to challenge 4
The Mock LISA Data Challenges are a program to demonstrate LISA data-analysis capabilities and to encourage their development. Each round of challenges consists of one or more datasets containing simulated instrument noise and gravitational waves from sources of undisclosed parameters. Participants analyze the datasets and report best-fit solutions for the source parameters. Here we present the results of the third challenge, issued in April 2008, which demonstrated the positive recovery of signals from chirping galactic binaries, from spinning supermassive-black-hole binaries (with optimal SNRs between ~10 and 2000), from simultaneous extreme-mass-ratio inspirals (SNRs of 10–50), from cosmic-string-cusp bursts (SNRs of 10–100), and from a relatively loud isotropic background with Ω_(gw)(f) ~ 10^(−11), slightly below the LISA instrument noise
The search for spinning black hole binaries in mock LISA data using a genetic algorithm
Coalescing massive Black Hole binaries are the strongest and probably the
most important gravitational wave sources in the LISA band. The spin and
orbital precessions bring complexity in the waveform and make the likelihood
surface richer in structure as compared to the non-spinning case. We introduce
an extended multimodal genetic algorithm which utilizes the properties of the
signal and the detector response function to analyze the data from the third
round of mock LISA data challenge (MLDC 3.2). The performance of this method is
comparable, if not better, to already existing algorithms. We have found all
five sources present in MLDC 3.2 and recovered the coalescence time, chirp
mass, mass ratio and sky location with reasonable accuracy. As for the orbital
angular momentum and two spins of the Black Holes, we have found a large number
of widely separated modes in the parameter space with similar maximum
likelihood values.Comment: 25 pages, 9 figure
Resolving Super Massive Black Holes with LISA
We study the angular resolution of the gravitational wave detector LISA and
show that numerical relativity can drastically improve the accuracy of position
location for coalescing Super Massive Black Hole (SMBH) binaries. For systems
with total redshifted mass above , LISA will mainly see the
merger and ring-down of the gravitational wave (GW) signal, which can now be
computed numerically using the full Einstein equations. Using numerical
waveforms that also include about ten GW cycles of inspiral, we improve
inspiral-only position estimates by an order of magnitude. We show that LISA
localizes half of all such systems at to better than 3 arcminutes and the
best 20% to within one arcminute. This will give excellent prospects for
identifying the host galaxy.Comment: 4 pages, 1 figur
Forced motion near black holes
We present two methods for integrating forced geodesic equations in the Kerr spacetime. The methods can accommodate arbitrary forces. As a test case, we compute inspirals caused by a simple drag force, mimicking motion in the presence of gas.We verify that both methods give the same results for this simple force. We find that drag generally causes eccentricity to increase throughout the inspiral. This is a relativistic effect qualitatively opposite to what is seen in gravitational-radiation-driven inspirals, and similar to what others have observed in hydrodynamic simulations of gaseous binaries. We provide an
analytic explanation by deriving the leading order relativistic correction to the Newtonian dynamics. If
observed, an increasing eccentricity would thus provide clear evidence that the inspiral was occurring in a
nonvacuum environment. Our two methods are especially useful for evolving orbits in the adiabatic regime. Both use the method of osculating orbits, in which each point on the orbit is characterized by the parameters of the geodesic with the same instantaneous position and velocity. Both methods describe the orbit in terms of the geodesic energy, axial angular momentum, Carter constant, azimuthal phase, and two angular variables that increase monotonically and are relativistic generalizations of the eccentric anomaly. The two methods differ in their treatment of the orbital phases and the representation of the force. In the first method, the geodesic phase and phase constant are evolved together as a single orbital phase parameter, and the force is expressed in terms of its components on the Kinnersley orthonormal tetrad. In
the second method, the phase constants of the geodesic motion are evolved separately and the force is
expressed in terms of its Boyer-Lindquist components. This second approach is a direct generalization of earlier work by Pound and Poisson [A. Pound and E. Poisson, Phys. Rev. D 77, 044013 (2008).] for planar forces in a Schwarzschild background
Detectability and parameter estimation of GWTC-3 events with LISA
Multiband observations of coalescing stellar-mass black holes binaries could
deliver valuable information on the formation of those sources and potential
deviations from General Relativity. Some of these binaries might be first
detected by the space-based detector LISA and, then, several years later,
observed with ground-based detectors. Due to large uncertainties in
astrophysical models, it is hard to predict the population of such binaries
that LISA could observe. In this work, we assess the ability of LISA to detect
the events of the third catalogue of gravitational wave sources released by the
LIGO/Virgo/KAGRA collaboration. We consider the possibility of directly
detecting the source with LISA and performing archival searches in the LISA
data stream, after the event has been observed with ground-based detectors. We
also assess how much could LISA improve the determination of source parameters.
We find that it is not guaranteed that any event other than GW150914 would have
been detected. Nevertheless, if any event is detected by LISA, even with a very
low signal-to-noise ratio, the measurement of source parameters would improve
by combining observations of LISA and ground based detectors, in particular for
the chirp mass.Comment: 10 pages, 11 figure
The search for black hole binaries using a genetic algorithm
In this work we use genetic algorithm to search for the gravitational wave
signal from the inspiralling massive Black Hole binaries in the simulated LISA
data. We consider a single signal in the Gaussian instrumental noise. This is a
first step in preparation for analysis of the third round of the mock LISA data
challenge. We have extended a genetic algorithm utilizing the properties of the
signal and the detector response function. The performance of this method is
comparable, if not better, to already existing algorithms.Comment: 11 pages, 4 figures, proceeding for GWDAW13 (Puerto Rico
Computation of stochastic background from extreme mass ratio inspiral populations for LISA
Extreme mass ratio inspirals (EMRIs) are among the primary targets for the
Laser Interferometer Space Antenna (LISA). The extreme mass ratios of these
systems result in relatively weak GW signals, that can be individually resolved
only for cosmologically nearby sources (up to ). The incoherent
piling up of the signal emitted by unresolved EMRIs generate a confusion noise,
that can be formally treated as a stochastic GW background (GWB). In this
paper, we estimate the level of this background considering a collection of
astrophysically motivated EMRI models, spanning the range of uncertainties
affecting EMRI formation. To this end, we employed the innovative Augmented
Analytic Kludge waveforms and used the full LISA response function. For each
model, we compute the GWB SNR and the number of resolvable sources. Compared to
simplified computations of the EMRI signals from the literature, we find that
for a given model the GWB SNR is lower by a factor of whereas the
number of resolvable sources drops by a factor 3-to-5. Nonetheless, the vast
majority of the models result in potentially detectable GWB which can also
significantly contribute to the overall LISA noise budget in the 1-10 mHz
frequency range
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