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ABSTRACT: We review the tests of general relativity that will become possible with
space-based gravitational-wave detectors operating in the ~0.01mHz - 1Hz
low-frequency band. The fundamental aspects of gravitation that can be tested
include the presence of additional gravitational fields other than the metric;
the number and tensorial nature of gravitational-wave polarization states; the
velocity of propagation of gravitational waves; the binding energy and
gravitational-wave radiation of binaries, and therefore the time evolution of
binary inspirals; the strength and shape of the waves emitted from binary
mergers and ringdowns; the true nature of astrophysical black holes; and much
more. The strength of this science alone calls for the swift implementation of
a space-based detector; the remarkable richness of astrophysics, astronomy, and
cosmology in the low-frequency gravitational-wave band make the case even
stronger.
12/2012;
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ABSTRACT: Space-based gravitational wave interferometers are sensitive to the galactic
population of ultra-compact binaries. An important subset of the ultra-compact
binary population are those stars that can be individually resolved by both
gravitational wave interferometers and electromagnetic telescopes. The aim of
this paper is to quantify the multi-messenger potential of space-based
interferometers with arm-lengths between 1 and 5 Gm. The Fisher Information
Matrix is used to estimate the number of binaries from a model of the Milky Way
which are localized on the sky by the gravitational wave detector to within 1
and 10 square degrees and bright enough to be detected by a magnitude limited
survey. We find, depending on the choice of GW detector characteristics,
limiting magnitude, and observing strategy, that up to several hundred
gravitational wave sources could be detected in electromagnetic follow-up
observations.
07/2012;
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Stanislav Babak,
John G. Baker,
Matthew J. Benacquista,
Neil J. Cornish, Shane L. Larson,
Ilya Mandel,
Sean T. McWilliams,
Antoine Petiteau,
Edward K. Porter,
Emma L. Robinson, [......],
Philip Graff,
Mike Hobson,
Joey Shapiro Key,
Andrzej Królak,
Anthony Lasenby,
Reinhard Prix,
Yu Shang,
Miquel Trias,
John Veitch,
John T. Whelan
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ABSTRACT: 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 Apr 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 Omega_gw(f) ~ 10^-11, slightly below the LISA instrument noise. Comment: 12 pages, 2 figures, proceedings of the 8th Edoardo Amaldi Conference on Gravitational Waves, New York, June 21-26, 2009
12/2009;
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ABSTRACT: Many scenarios have been proposed for the origin of the supermassive black holes (SMBHs) that are found in the centres of most galaxies. Many of these formation scenarios predict a high-redshift population of intermediate-mass black holes (IMBHs), with masses in the range 100 to 100000 times that of the Sun. A powerful way to observe these IMBHs is via gravitational waves the black holes emit as they merge. The statistics of the observed black hole population should, in principle, allow us to discriminate between competing astrophysical scenarios for the origin and formation of SMBHs. However, gravitational wave detectors such as LISA will not be able to detect all such mergers nor assign precise black hole parameters to the merger, due to weak gravitational wave signal strengths. In order to use LISA observations to infer the statistics of the underlying population, these errors must be taken into account. We describe here a method for folding the LISA gravitational wave parameter error estimates into an `error kernel' designed for use at the population model level. The effects of this error function are demonstrated by applying it to several recent models of black hole mergers, and some tentative conclusions are made about LISA's ability to test scenarios of the origin and formation of supermassive black holes. Comment: 22 pages, 4 figures. There have been various clarifications, typos corrected, and so on, partly in response to referee comments. This second arXiv version has been switched to AASTeX preprint format for better compatibility with the arXiv. Accepted for publication in MNRAS
03/2009;
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ABSTRACT: High altitude balloon platforms are ideal for providing hands-on research experiences for students in physics, atmospheric science, engineering, and other aerospace-related disciplines. We describe a basic high altitude balloon platform that can be constructed and operated by undergraduate students. The existing HARBOR and BOREALIS programs are used to illustrate some possible science and engineering research projects that students can pursue as part of a high-altitude flight program.
Am. J. Phys. 01/2009; 77(489).
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ABSTRACT: General expressions for the expected timing residuals induced by gravitational wave (G-wave) emission from a slowly evolving, eccentric, binary black hole system are derived here for the first time. These expressions are used to search for the signature of G-waves emitted by the proposed supermassive binary black hole system in 3C 66B. We use data from long-term timing observations of the radio pulsar PSR B1855+09. For the case of a circular orbit, the emitted G-waves should generate clearly detectable fluctuations in the pulse-arrival times of PSR B1855+09. Since no G-waves are detected, the waveforms are used in a Monte Carlo analysis in order to place limits on the mass and eccentricity of the proposed black hole system. The analysis presented here rules out the adopted system with 95% confidence. The reported analysis also demonstrates several interesting features of a G-wave detector based on pulsar timing.
The Astrophysical Journal 12/2008; 606(2):799. · 6.02 Impact Factor
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ABSTRACT: Detection of a gravitational-wave stochastic background via ground or space-based gravitational-wave detectors requires the cross-correlation of the response of two or more independent detectors. The cross-correlation involves a frequency-dependent factor -- the so-called overlap reduction function or Hellings-Downs curve -- that depends on the relative geometry of each detector pair: i.e., the detector separations and the relative orientation of their antenna patterns (beams). An incorrect formulation of this geometrical factor has appeared in the literature, leading to incorrect conclusions regarding the sensitivity of proposed detectors to a stochastic gravitational-wave background. To rectify these errors and as a reference for future work we provide here a complete, first-principles derivation of the overlap reduction function and assess the nature of the errors associated with the use of the incorrect expression that has appeared in the literature. We describe the behavior of the overlap reduction function in different limiting regimes, and show how the difference between the correct and incorrect expressions can be understood physically. Comment: Removed incorrect references to the Seto and Taruya papers; added explicit expression for the detector transfer function; final published version
11/2008;
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Stanislav Babak,
John G. Baker,
Matthew J. Benacquista,
Neil J. Cornish,
Jeff Crowder, Shane L. Larson,
Eric Plagnol,
Edward K. Porter,
Michele Vallisneri,
Alberto Vecchio, [......],
Ilya Mandel,
Reinhard Prix,
B. S. Sathyaprakash,
Pavlin Savov,
Yu Shang,
Miquel Trias,
John Veitch,
Yan Wang,
Linqing Wen,
John T. Whelan
[show abstract]
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ABSTRACT: The Mock LISA Data Challenges are a programme to demonstrate and encourage the development of LISA data-analysis capabilities, tools and techniques. At the time of this workshop, three rounds of challenges had been completed, and the next was about to start. In this article we provide a critical analysis of entries to the latest completed round, Challenge 1B. The entries confirm the consolidation of a range of data-analysis techniques for Galactic and massive--black-hole binaries, and they include the first convincing examples of detection and parameter estimation of extreme--mass-ratio inspiral sources. In this article we also introduce the next round, Challenge 3. Its data sets feature more realistic waveform models (e.g., Galactic binaries may now chirp, and massive--black-hole binaries may precess due to spin interactions), as well as new source classes (bursts from cosmic strings, isotropic stochastic backgrounds) and more complicated nonsymmetric instrument noise.
07/2008;
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Stanislav Babak,
John G. Baker,
Matthew J. Benacquista,
Neil J. Cornish,
Jeff Crowder,
Curt Cutler, Shane L. Larson,
Tyson B. Littenberg,
Edward K. Porter,
Michele Vallisneri, [......],
Emma L. Robinson,
Christian Roever,
Pavlin Savov,
Alexander Stroeer,
Jennifer Toher,
John Veitch,
Jean-Yves Vinet,
Linqing Wen,
John T. Whelan,
Graham Woan
[show abstract]
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ABSTRACT: 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 several data sets containing simulated instrument noise and gravitational-wave sources of undisclosed parameters. Participants are asked to analyze the data sets and report the maximum information about source parameters. The challenges are being released in rounds of increasing complexity and realism: in this proceeding we present the results of Challenge 2, issued in January 2007, which successfully demonstrated the recovery of signals from supermassive black-hole binaries, from ~20,000 overlapping Galactic white-dwarf binaries, and from the extreme-mass-ratio inspirals of compact objects into central galactic black holes.
12/2007;
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ABSTRACT: The Testbed for LISA Analysis (TLA) Project aims to facilitate the development, validation, and comparison of different methods for LISA science data analysis by the broad LISA Science Community to meet the special challenges that LISA poses. It includes a well‐defined Simulated LISA Data Product (SLDP), which provides a clean interface between the modeling of LISA, the preparation of LISA data, and the analysis of the LISA science data stream; a web‐based clearinghouse (at 〈http://tla.gravity.psu.edu〉) providing SLDP software libraries, relevant software, papers and other documentation, and a repository for SLDP data sets; a set of mailing lists for communication between and among LISA simulator developers and LISA science analysts; a problem tracking system for SLDP support; and a program of workshops to allow the burgeoning LISA science community to further refine the SLDP definition, define specific LISA science analysis challenges, and report their results. This proceedings paper describes the TLA Project, the resources it provides immediately, its future plans, and invites the participation of the broader community in the furtherance of its goals. © 2006 American Institute of Physics
AIP Conference Proceedings. 11/2006; 873(1):640-644.
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ABSTRACT: The capture of compact bodies by black holes in galactic nuclei is an important prospective source for low frequency gravitational wave detectors, such as the planned Laser Interferometer Space Antenna. This paper calculates, using a semirelativistic approximation, the total energy and angular momentum lost to gravitational radiation by compact bodies on very high eccentricity orbits passing close to a supermassive, nonspinning black hole; these quantities determine the characteristics of the orbital evolution necessary to estimate the capture rate. The semirelativistic approximation improves upon treatments which use orbits at Newtonian order and quadrupolar radiation emission, and matches well onto accurate Teukolsky simulations for low eccentricity orbits. Formulas are presented for the semirelativistic energy and angular momentum fluxes as a function of general orbital parameters.
Phys. Rev. D. 11/2006; 74(10).
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ABSTRACT: In this paper we introduce a hands-on activity in which introductory astronomy students act as gravitational wave astronomers by extracting information from simulated gravitational wave signals. The process mimics the way true gravitational wave analysis will be handled by using plots of a pure gravitational wave signal. The students directly measure the properties of the simulated signal, and use these measurements to evaluate standard formulae for astrophysical source parameters. An exercise based on the discussion in this paper has been written and made publicly available online for use in introductory laboratory courses.
11/2006;
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ABSTRACT: The principal goal of the \emph{LISA Science Analysis Workshop} is to encourage the development and maturation of science analysis technology in preparation for LISA science operations. Exactly because LISA is a pathfinder for a new scientific discipline -- gravitational wave astronomy -- LISA data processing and science analysis methodologies are in their infancy and require considerable maturation if they are to be ready to take advantage of LISA data. Here we offer some thoughts, in anticipation of the LISA Science Analysis Workshop, on analysis research problems that demonstrate the capabilities of different proposed analysis methodologies and, simultaneously, help to push those techniques toward greater maturity. Particular emphasis is placed on formulating questions that can be turned into well-posed problems involving tests run on specific data sets, which can be shared among different groups to enable the comparison of techniques on a well-defined platform.
07/2006;
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[show abstract]
[hide abstract]
ABSTRACT: The Testbed for LISA Analysis (TLA) Project aims to facilitate the development, validation and comparison of different methods for LISA science data analysis, by the broad LISA Science Community, to meet the special challenges that LISA poses. It includes a well-defined Simulated LISA Data Product (SLDP), which provides a clean interface between the communities that have developed to model and to analyze the LISA science data stream; a web-based clearinghouse (at <http://tla.gravity.psu.edu>) providing SLDP software libraries, relevant software, papers and other documentation, and a repository for SLDP data sets; a set of mailing lists for communication between and among LISA simulators and LISA science analysts; a problem tracking system for SLDP support; and a program of workshops to allow the burgeoning LISA science community to further refine the SLDP definition, define specific LISA science analysis challenges, and report their results. This note describes the TLA Project, the resources it provides immediately, its future plans, and invites the participation of the broader community in the furtherance of its goals.
03/2006;
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[show abstract]
[hide abstract]
ABSTRACT: The capture of compact bodies by black holes in galactic nuclei is an important prospective source for low frequency gravitational wave detectors, such as the planned Laser Interferometer Space Antenna. This paper calculates, using a semirelativistic approximation, the total energy and angular momentum lost to gravitational radiation by compact bodies on very high eccentricity orbits passing close to a supermassive, nonspinning black hole; these quantities determine the characteristics of the orbital evolution necessary to estimate the capture rate. The semirelativistic approximation improves upon treatments which use orbits at Newtonian order and quadrupolar radiation emission, and matches well onto accurate Teukolsky simulations for low eccentricity orbits. Formulas are presented for the semirelativistic energy and angular momentum fluxes as a function of general orbital parameters.
Phys. Rev. D. 10/2005; 72(8).
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ABSTRACT: This article reviews the current status of gravitational wave astronomy and explains why astronomers are excited about the new generation of gravitational wave detectors. As part of the review we compare and contrast gravitational radiation to the more familiar electromagnetic radiation. We discuss the current indirect experimental evidence for gravitational waves, and how current and future gravitational wave detectors will operate as our newest telescopes pointed at the skies. Comment: See related hands-on activity at physics/0503198. Accepted to The Physics Teacher
09/2005;
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[show abstract]
[hide abstract]
ABSTRACT: The capture of compact bodies by black holes in galactic nuclei is an important prospective source for low frequency gravitational wave detectors, such as the planned Laser Interferometer Space Antenna. This paper calculates, using a semirelativistic approximation, the total energy and angular momentum lost to gravitational radiation by compact bodies on very high eccentricity orbits passing close to a supermassive, nonspinning black hole; these quantities determine the characteristics of the orbital evolution necessary to estimate the capture rate. The semirelativistic approximation improves upon treatments which use orbits at Newtonian-order and quadrupolar radiation emission, and matches well onto accurate Teukolsky simulations for low eccentricity orbits. Formulae are presented for the semirelativistic energy and angular momentum fluxes as a function of general orbital parameters. Comment: 27 pages, 12 figures; v2: revised manuscript includes small changes to make paper consistent with published version; v3: a statement about how to generalise our results to hyperbolic orbits was incorrect, new version includes published erratum as an appendix
08/2005;
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ABSTRACT: The capture and inspiral of compact stellar masses into massive black holes is an important source of low-frequency gravitational waves (with frequencies of ~1-100mHz), such as those that might be detected by the planned Laser Interferometer Space Antenna (LISA). Simulations of stellar clusters designed to study this problem typically rely on simple treatments of the black hole encounter which neglect some important features of orbits around black holes, such as the minimum radii of stable, non-plunging orbits. Incorporating an accurate representation of the orbital dynamics near a black hole has been avoided due to the large computational overhead. This paper provides new, more accurate, expressions for the energy and angular momentum lost by a compact object during a parabolic encounter with a non-spinning black hole, and the subsequent inspiral lifetime. These results improve on the Keplerian expressions which are now commonly used and will allow efficient computational simulations to be performed that account for the relativistic nature of the spacetime around the central black hole in the system. Comment: 19 pages, 4 figures. Changed in response to referee's report. Accepted for publication in Astrophysical Journal
08/2005;
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ABSTRACT: At the beginning of a class or meeting an icebreaker activity is often used to help loosen the group and get everyone talking. Our motivation is to develop activities that serve the purpose of an icebreaker, but are designed to enhance and supplement a science-oriented agenda. The subject of this article is an icebreaker activity related to gravitational wave astronomy. We first describe the unique gravitational wave signals from three distinct sources: monochromatic binaries, merging compact objects, and extreme mass ratio encounters. These signals form the basis of the activity where participants work to match an ideal gravitational wave signal with noisy detector output for each type of source. Comment: Accepted to The Physics Teacher. Original manuscript divided into two papers at the request of the referee. For a related paper on gravitational wave observatories see physics/0509201
03/2005;
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ABSTRACT: One of the most exciting prospects for the LISA gravitational wave observatory is the detection of gravitational radiation from the inspiral of a compact object into a supermassive black hole. The large inspiral parameter space and low amplitude of the signal makes detection of these sources computationally challenging. We outline here a first cut data analysis scheme that assumes realistic computational resources. In the context of this scheme, we estimate the signal-to-noise ratio that a source requires to pass our thresholds and be detected. Combining this with an estimate of the population of sources in the Universe, we estimate the number of inspiral events that LISA could detect. The preliminary results are very encouraging -- with the baseline design, LISA can see inspirals out to a redshift z=1 and should detect over a thousand events during the mission lifetime. Comment: 15 pages, 1 figure, to appear in GWDAW 8 proceedings
05/2004;
