121 research outputs found
Coherently combining short data segments for all-sky semi-coherent continuous gravitational wave searches
We present a method for coherently combining short data segments from
gravitational-wave detectors to improve the sensitivity of semi-coherent
searches for continuous gravitational waves. All-sky searches for continuous
gravitational waves from unknown sources are computationally limited. The
semi-coherent approach reduces the computational cost by dividing the entire
observation timespan into short segments to be analyzed coherently, then
combined together incoherently. Semi-coherent analyses that attempt to improve
sensitivity by coherently combining data from multiple detectors face a
computational challenge in accounting for uncertainties in signal parameters.
In this article, we lay out a technique to meet this challenge using summed
Fourier transform coefficients. Applying this technique to one all-sky search
algorithm called TwoSpect, we confirm that the sensitivity of all-sky,
semi-coherent searches can be improved by coherently combining the short data
segments. For misaligned detectors, however, this improvement requires careful
attention when marginalizing over unknown polarization parameters. In addition,
care must be taken in correcting for differential detector velocity due to the
Earth's rotation for high signal frequencies and widely separated detectors.Comment: 15 pages, 3 figures, 1 tabl
Efficient Estimation of Barycentered Relative Time Delays for Distant Gravitational Wave Sources
Accurate determination of gravitational wave source parameters relies on
transforming between the source and detector frames. All-sky searches for
continuous wave sources are computationally expensive, in part, because of
barycentering transformation of time delays to a solar system frame. This
expense is exacerbated by the complicated modulation induced in signal
templates. We investigate approximations for determining time delays of signals
received by a gravitational wave detector with respect to the solar system
barycenter. A highly non-linear conventional computation is transformed into
one that has a pure linear sum in its innermost loop. We discuss application of
these results to determination of the maximal useful integration time of
continuous wave searches
An all-sky search algorithm for continuous gravitational waves from spinning neutron stars in binary systems
Rapidly spinning neutron stars with non-axisymmetric mass distributions are expected to generate quasi-monochromatic continuous gravitational waves. While many searches for unknown, isolated spinning neutron stars have been carried out, there have been no previous searches for unknown sources in binary systems. Since current search methods for unknown, isolated neutron stars are already computationally limited, expanding the parameter space searched to include binary systems is a formidable challenge. We present a new hierarchical binary search method called TwoSpect, which exploits the periodic orbital modulations of the continuous waves by searching for patterns in doubly Fourier-transformed data. We will describe the TwoSpect search pipeline, including its mitigation of detector noise variations and corrections for Doppler frequency modulation caused by changing detector velocity. Tests on Gaussian noise and on a set of simulated signals will be presented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90779/1/0264-9381_28_21_215006.pd
High-precision Absolute Distance Measurement using Dual-Laser Frequency Scanned Interferometry Under Realistic Conditions
In this paper, we report on new high-precision absolute distance measurements
performed with frequency scanned interferometry using a pair of single-mode
optical fibers. Absolute distances were determined by counting the interference
fringes produced while scanning the frequencies of the two chopped lasers.
High-finesse Fabry-Perot interferometers were used to determine frequency
changes during scanning. Dual lasers with oppositely scanning directions,
combined with a multi-distance-measurement technique previously reported, were
used to cancel drift errors and to suppress vibration effects and interference
fringe uncertainties. Under realistic conditions, a precision about 0.2 microns
was achieved for a distance of 0.41 meters.Comment: 14 pages, 5 figures, submitted to Applied Optic
Astronomy\u27s New Messengers: A Traveling Exhibit on Gravitational-Wave Physics
The Laser Interferometer Gravitational-wave Observatory exhibit Astronomy\u27s New Messengers: Listening to the Universe with Gravitational Waves is traveling to colleges, universities, museums and other public institutions throughout the United States. Astronomy\u27s New Messengers primarily communicates with an adolescent and young adult audience, potentially inspiring them into the field of science. Acknowledging that this audience is traditionally a difficult one to attract, the exhibit publicly announces itself in a charismatic fashion to reach its principal goals of broadening the community of people interested in science and encouraging interest in science among young people
Astronomy\u27s New Messengers: A Traveling Exhibit to Reach Out to a Young Adult Audience
The Laser Interferometer Gravitational-wave Observatory exhibit Astronomy\u27s New Messengers: Listening to the Universe with Gravitational Waves is traveling to colleges, universities, museums and other public institutions throughout the United States. In 2010, an extended version of this exhibit will appear in a New York City venue that is accessible to a large and diverse cross section of the general public. Astronomy\u27s New Messengers primarily communicates with an adolescent and young adult audience, potentially inspiring them into the field of science. Acknowledging that this audience is traditionally a difficult one to attract, the exhibit publicly announces itself in a charismatic fashion to reach its principal goals of broadening the community of people interested in science and encouraging interest in science among young people
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