35 research outputs found
Forward Modeling of Space-borne Gravitational Wave Detectors
Planning is underway for several space-borne gravitational wave observatories
to be built in the next ten to twenty years. Realistic and efficient forward
modeling will play a key role in the design and operation of these
observatories. Space-borne interferometric gravitational wave detectors operate
very differently from their ground based counterparts. Complex orbital motion,
virtual interferometry, and finite size effects complicate the description of
space-based systems, while nonlinear control systems complicate the description
of ground based systems. Here we explore the forward modeling of space-based
gravitational wave detectors and introduce an adiabatic approximation to the
detector response that significantly extends the range of the standard low
frequency approximation. The adiabatic approximation will aid in the
development of data analysis techniques, and improve the modeling of
astrophysical parameter extraction.Comment: 14 Pages, 14 Figures, RevTex
Noise characterization for LISA
We consider the general problem of estimating the inflight LISA noise power
spectra and cross-spectra, which are needed for detecting and estimating the
gravitational wave signals present in the LISA data. For the LISA baseline
design and in the long wavelength limit, we bound the error on all spectrum
estimators that rely on the use of the fully symmetric Sagnac combination
(). This procedure avoids biases in the estimation that would otherwise
be introduced by the presence of a strong galactic background in the LISA data.
We specialize our discussion to the detection and study of the galactic white
dwarf-white dwarf binary stochastic signal.Comment: 9 figure
Optimal filtering of the LISA data
The LISA time-delay-interferometry responses to a gravitational-wave signal
are rewritten in a form that accounts for the motion of the LISA constellation
around the Sun; the responses are given in closed analytic forms valid for any
frequency in the band accessible to LISA. We then present a complete procedure,
based on the principle of maximum likelihood, to search for stellar-mass binary
systems in the LISA data. We define the required optimal filters, the
amplitude-maximized detection statistic (analogous to the F statistic used in
pulsar searches with ground-based interferometers), and discuss the false-alarm
and detection probabilities. We test the procedure in numerical simulations of
gravitational-wave detection.Comment: RevTeX4, 28 pages, 9 EPS figures. Minus signs fixed in Eq. (46) and
Table II. Corrected discussion of F-statistic distribution in Sec. IV
Annual modulation of the Galactic binary confusion noise bakground and LISA data analysis
We study the anisotropies of the Galactic confusion noise background and its
effects on LISA data analysis. LISA has two data streams of the gravitational
waves signals relevant for low frequency regime. Due to the anisotropies of the
background, the matrix for their confusion noises has off-diagonal components
and depends strongly on the orientation of the detector plane. We find that the
sky-averaged confusion noise level could change by a factor of 2
in three months, and would be minimum when the orbital position of LISA is
either around the spring or autumn equinox.Comment: 13 pages, 6 figure
Sagnac Interferometer as a Speed-Meter-Type, Quantum-Nondemolition Gravitational-Wave Detector
According to quantum measurement theory, "speed meters" -- devices that
measure the momentum, or speed, of free test masses -- are immune to the
standard quantum limit (SQL). It is shown that a Sagnac-interferometer
gravitational-wave detector is a speed meter and therefore in principle it can
beat the SQL by large amounts over a wide band of frequencies. It is shown,
further, that, when one ignores optical losses, a signal-recycled Sagnac
interferometer with Fabry-Perot arm cavities has precisely the same
performance, for the same circulating light power, as the Michelson speed-meter
interferometer recently invented and studied by P. Purdue and the author. The
influence of optical losses is not studied, but it is plausible that they be
fairly unimportant for the Sagnac, as for other speed meters. With squeezed
vacuum (squeeze factor ) injected into its dark port, the
recycled Sagnac can beat the SQL by a factor over the
frequency band 10 {\rm Hz} \alt f \alt 150 {\rm Hz} using the same
circulating power kW as is used by the (quantum limited)
second-generation Advanced LIGO interferometers -- if other noise sources are
made sufficiently small. It is concluded that the Sagnac optical configuration,
with signal recycling and squeezed-vacuum injection, is an attractive candidate
for third-generation interferometric gravitational-wave detectors (LIGO-III and
EURO).Comment: 12 pages, 6 figure
Experimental characterization of continuous-variable entanglement
We present an experimental analysis of quadrature entanglement produced from a pair of amplitude squeezed beams. The correlation matrix of the state is characterized within a set of reasonable assumptions, and the strength of the entanglement is gauged using measures of the degree of inseparability and the degree of Einstein-Podolsky-Rosen (EPR) paradox. We introduce controlled decoherence in the form of optical loss to the entangled state, and demonstrate qualitative differences in the response of the degrees of inseparability and EPR paradox to this loss. The entanglement is represented on a photon number diagram that provides an intuitive and physically relevant description of the state. We calculate efficacy contours for several quantum information protocols on this diagram, and use them to predict the effectiveness of our entanglement in those protocols
All-sky search for long-duration gravitational wave transients with initial LIGO
We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society
All-sky search for long-duration gravitational wave transients with initial LIGO
We present the results of a search for long-duration gravitational wave transients in two sets of data collected by the LIGO Hanford and LIGO Livingston detectors between November 5, 2005 and September 30, 2007, and July 7, 2009 and October 20, 2010, with a total observational time of 283.0 days and 132.9 days, respectively. The search targets gravitational wave transients of duration 10-500 s in a frequency band of 40-1000 Hz, with minimal assumptions about the signal waveform, polarization, source direction, or time of occurrence. All candidate triggers were consistent with the expected background; as a result we set 90% confidence upper limits on the rate of long-duration gravitational wave transients for different types of gravitational wave signals. For signals from black hole accretion disk instabilities, we set upper limits on the source rate density between 3.4×10-5 and 9.4×10-4 Mpc-3 yr-1 at 90% confidence. These are the first results from an all-sky search for unmodeled long-duration transient gravitational waves. © 2016 American Physical Society
Search for gravitational waves from Scorpius X-1 in the second Advanced LIGO observing run with an improved hidden Markov model
We present results from a semicoherent search for continuous gravitational waves from the low-mass x-ray binary Scorpius X-1, using a hidden Markov model (HMM) to track spin wandering. This search improves on previous HMM-based searches of LIGO data by using an improved frequency domain matched filter, the J-statistic, and by analyzing data from Advanced LIGO's second observing run. In the frequency range searched, from 60 to 650 Hz, we find no evidence of gravitational radiation. At 194.6 Hz, the most sensitive search frequency, we report an upper limit on gravitational wave strain (at 95% confidence) of h095%=3.47×10-25 when marginalizing over source inclination angle. This is the most sensitive search for Scorpius X-1, to date, that is specifically designed to be robust in the presence of spin wandering. © 2019 American Physical Society