194 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
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
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
Verifying the no-hair property of massive compact objects with intermediate-mass-ratio inspirals in advanced gravitational-wave detectors
The detection of gravitational waves from the inspiral of a neutron star or
stellar-mass black hole into an intermediate-mass black hole (IMBH) promises an
entirely new look at strong-field gravitational physics. Gravitational waves
from these intermediate-mass-ratio inspirals (IMRIs), systems with mass ratios
from ~10:1 to ~100:1, may be detectable at rates of up to a few tens per year
by Advanced LIGO/Virgo and will encode a signature of the central body's
spacetime. Direct observation of the spacetime will allow us to use the
"no-hair" theorem of general relativity to determine if the IMBH is a Kerr
black hole (or some more exotic object, e.g. a boson star). Using modified
post-Newtonian (pN) waveforms, we explore the prospects for constraining the
central body's mass-quadrupole moment in the advanced-detector era. We use the
Fisher information matrix to estimate the accuracy with which the parameters of
the central body can be measured. We find that for favorable mass and spin
combinations, the quadrupole moment of a non-Kerr central body can be measured
to within a ~15% fractional error or better using 3.5 pN order waveforms; on
the other hand, we find the accuracy decreases to ~100% fractional error using
2 pN waveforms, except for a narrow band of values of the best-fit non-Kerr
quadrupole moment.Comment: Second version, 12 pages, 5 figures, accepted by PR
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