1,210 research outputs found
Approximate waveform templates for detection of extreme mass ratio inspirals with LISA
The inspirals of compact objects into massive black holes are some of the
most exciting of the potential sources of gravitational waves for the planned
Laser Interferometer Space Antenna (LISA). Observations of such extreme mass
ratio inspirals (EMRIs) will not only reveal to us the properties of black
holes in the Universe, but will allow us to verify that the space-time
structure around massive compact objects agrees with the predictions of
relativity. Detection of EMRI signals via matched filtering and interpretation
of the observations will require models of the gravitational waveforms. The
extreme mass ratio allows accurate waveforms to be computed from black hole
perturbation theory, but this is computationally expensive and has not yet been
fully developed. Ongoing research to scope out LISA data analysis algorithms
requires waveforms that can be generated quickly in large numbers. To fulfil
this purpose, families of approximate, "kludge", EMRI waveforms have been
developed that capture the main features of true EMRI waveforms, but that can
also be generated for a comparatively small computational cost. In this
proceedings article, we briefly outline one such waveform family (the
"numerical kludge"), its accuracy and some possible ways in which it might be
improved in the future. Although accurate parameter extraction will require use
of perturbative waveforms, these approximate waveforms are sufficiently
faithful to the true waveforms that they may be able to play a role in
detection of EMRIs in the LISA data.Comment: 3 pages; to appear in Proceedings of the Eleventh Marcel Grossmann
meetin
Time-frequency analysis of extreme-mass-ratio inspiral signals in mock LISA data
Extreme-mass-ratio inspirals (EMRIs) of ~ 1-10 solar-mass compact objects
into ~ million solar-mass massive black holes can serve as excellent probes of
strong-field general relativity. The Laser Interferometer Space Antenna (LISA)
is expected to detect gravitational wave signals from apprxomiately one hundred
EMRIs per year, but the data analysis of EMRI signals poses a unique set of
challenges due to their long duration and the extensive parameter space of
possible signals. One possible approach is to carry out a search for EMRI
tracks in the time-frequency domain. We have applied a time-frequency search to
the data from the Mock LISA Data Challenge (MLDC) with promising results. Our
analysis used the Hierarchical Algorithm for Clusters and Ridges to identify
tracks in the time-frequency spectrogram corresponding to EMRI sources. We then
estimated the EMRI source parameters from these tracks. In these proceedings,
we discuss the results of this analysis of the MLDC round 1.3 data.Comment: Amaldi-7 conference proceedings; requires jpconf style file
Detecting LISA sources using time-frequency techniques
The planned Laser Interferometer Space Antenna (LISA) will detect
gravitational wave signals from a wide range of sources. However, disentangling
individual signals from the source-dominated data stream is a challenging
problem and the focus of much current research. The problems are particularly
acute for detection of extreme mass ratio inspirals (EMRIs), for which the
instantaneous signal amplitude is an order of magnitude below the level of the
instrumental noise, and the parameter space of possible signals is too large to
permit fully-coherent matched filtering. One possible approach is to attempt to
identify sources in a time-frequency spectrogram of the LISA data. This is a
computationally cheap method that may be useful as a first stage in a
hierarchical analysis. Initial results, evaluated using a significantly
simplified model of the LISA data stream, suggest that time-frequency
techniques might be able to detect the nearest few tens of EMRI events. In this
proceedings article, we briefly outline the methods that have so far been
applied to the problem, initial results and possible future directions for the
research.Comment: 3 pages; to appear in Proceedings of the Eleventh Marcel Grossmann
meetin
Approximate Waveforms for Extreme-Mass-Ratio Inspirals in Modified Gravity Spacetimes
Extreme-mass-ratio inspirals, in which a stellar-mass compact object spirals
into a supermassive black hole, are prime candidates for detection with
space-borne milliHertz gravitational wave detectors, similar to the Laser
Interferometer Space Antenna. The gravitational waves generated during such
inspirals encode information about the background in which the small object is
moving, providing a tracer of the spacetime geometry and a probe of
strong-field physics. In this paper, we construct approximate,
"analytic-kludge" waveforms for such inspirals with parameterized
post-Einsteinian corrections that allow for generic, model-independent
deformations of the supermassive black hole background away from the Kerr
metric. These approximate waveforms include all of the qualitative features of
true waveforms for generic inspirals, including orbital eccentricity and
relativistic precession. The deformations of the Kerr metric are modeled using
a recently proposed, modified gravity bumpy metric, which parametrically
deforms the Kerr spacetime while ensuring that three approximate constants of
the motion remain for geodesic orbits: a conserved energy, azimuthal angular
momentum and Carter constant. The deformations represent modified gravity
effects and have been analytically mapped to several modified gravity black
hole solutions in four dimensions. In the analytic kludge waveforms, the
conservative motion is modeled by a post-Newtonian expansion of the geodesic
equations in the deformed spacetimes, which in turn induce modifications to the
radiation-reaction force. These analytic-kludge waveforms serve as a first step
toward complete and model-independent tests of General Relativity with extreme
mass-ratio inspirals.Comment: v1: 28 pages, no figures; v2: minor changes for consistency with
accepted version, 2 figures added showing sample waveforms; accepted by Phys.
Rev.
Detecting extreme mass ratio inspirals with LISA using time-frequency methods II: search characterization
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.Comment: 15 pages, 9 figures, to appear in proceedings of GWDAW 9, Annecy,
France, December 200
Detecting extreme mass ratio inspirals with LISA using time–frequency methods
The inspirals of stellar-mass compact objects into supermassive black holes are some of the most important sources for LISA. Detection techniques based on fully coherent matched filtering have been shown to be computationally intractable. We describe an efficient and robust detection method that utilizes the time–frequency evolution of such systems. We show that a typical extreme mass ratio inspiral (EMRI) source could possibly be detected at distances of up to ~2 Gpc, which would mean ~tens of EMRI sources can be detected per year using this technique. We discuss the feasibility of using this method as a first step in a hierarchical search
Detecting extreme mass ratio inspiral events in LISA data using the Hierarchical Algorithm for Clusters and Ridges (HACR)
One of the most exciting prospects for the Laser Interferometer Space Antenna
(LISA) is the detection of gravitational waves from the inspirals of
stellar-mass compact objects into supermassive black holes. Detection of these
sources is an extremely challenging computational problem due to the large
parameter space and low amplitude of the signals. However, recent work has
suggested that the nearest extreme mass ratio inspiral (EMRI) events will be
sufficiently loud that they might be detected using computationally cheap,
template-free techniques, such as a time-frequency analysis. In this paper, we
examine a particular time-frequency algorithm, the Hierarchical Algorithm for
Clusters and Ridges (HACR). This algorithm searches for clusters in a power map
and uses the properties of those clusters to identify signals in the data. We
find that HACR applied to the raw spectrogram performs poorly, but when the
data is binned during the construction of the spectrogram, the algorithm can
detect typical EMRI events at distances of up to Gpc. This is a little
further than the simple Excess Power method that has been considered
previously. We discuss the HACR algorithm, including tuning for single and
multiple sources, and illustrate its performance for detection of typical EMRI
events, and other likely LISA sources, such as white dwarf binaries and
supermassive black hole mergers. We also discuss how HACR cluster properties
could be used for parameter extraction.Comment: 21 pages, 11 figures, submitted to Class. Quantum Gravity. Modified
and shortened in light of referee's comments. Updated results consider tuning
over all three HACR thresholds, and show 10-15% improvement in detection rat
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