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ABSTRACT: The cross-correlation search for gravitational wave, which is known as
'radiometry', has been previously applied to map of the gravitational wave
stochastic background in the sky and also to target on gravitational wave from
rotating neutron stars/pulsars. We consider the Virgo cluster where may be
appear as `hot spot' spanning few pixels in the sky in radiometry analysis. Our
results show that sufficient signal to noise ratio can be accumulated with
integration times of the order of a year. We also construct numerical
simulation of radiometry analysis, assuming current constructing/upgrading
ground-based detectors. Point spread function of the injected sources are
confirmed by numerical test. Typical resolution of radiometry analysis is a few
square degree which corresponds to several thousand pixels of sky mapping.
12/2011;
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ABSTRACT: The cross-correlation search has been previously applied to map the
gravitational wave (GW) stochastic background in the sky and also to target GW
from rotating neutron stars/pulsars. Here we investigate how the
cross-correlation method can be used to target a small region in the sky
spanning at most a few pixels, where a pixel in the sky is determined by the
diffraction limit which depends on the (i) baseline joining a pair of detectors
and (ii) detector bandwidth. Here as one of the promising targets, we consider
the Virgo cluster - a "hot spot" spanning few pixels - which could contain, as
estimates suggest $\sim 10^{11}$ neutron stars, of which a small fraction would
continuously emit GW in the bandwidth of the detectors. For the detector
baselines, we consider advanced detector pairs among LCGT, LIGO, Virgo, ET etc.
Our results show that sufficient signal to noise can be accumulated with
integration times of the order of a year. The results improve for the
multibaseline search. This analysis could as well be applied to other likely
hot spots in the sky and other possible pairs of detectors.
05/2011;
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ABSTRACT: We present the first upper limit on gravitational wave (GW) backgrounds at an unexplored frequency of 0.2 Hz using a torsion-bar antenna (TOBA). A TOBA was proposed to search for low-frequency GWs. We have developed a small-scaled TOBA and successfully found Ω(gw)(f)<4.3×10(17) at 0.2 Hz as demonstration of the TOBA's capabilities, where Ω(gw)(f) is the GW energy density per logarithmic frequency interval in units of the closure density. Our result is the first nonintegrated limit to bridge the gap between the LIGO band (around 100 Hz) and the Cassini band (10(-6)-10(-4) Hz).
Physical Review Letters 04/2011; 106(16):161101. · 7.37 Impact Factor
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Masaki Ando,
Seiji Kawamura,
Naoki Seto,
Shuichi Sato,
Takashi Nakamura,
Kimio Tsubono,
Takeshi Takashima,
Ikkoh Funaki,
Kenji Numata,
Nobuyuki Kanda, [......],
Yaka Wakabayashi,
Kent Yagi,
Hiroshi Yamakawa,
Kazuhiro Yamamoto,
Toshitaka Yamazaki,
Jun'ichi Yokoyama,
Chul-Moon Yoo,
Shijun Yoshida,
Taizoh Yoshino,
Ke-Xun Sun
[show abstract]
[hide abstract]
ABSTRACT: A space gravitational-wave antenna, DECIGO (DECI-hertz interferometer Gravitational wave Observatory), will provide fruitful insights into the universe, particularly on the formation mechanism of supermassive black holes, dark energy and the inflation of the universe. In the current pre-conceptual design, DECIGO will be comprising four interferometer units; each interferometer unit will be formed by three drag-free spacecraft with 1000 km separation. Since DECIGO will be an extremely challenging mission with high-precision formation flight with long baseline, it is important to increase the technical feasibility before its planned launch in 2027. Thus, we are planning to launch two milestone missions. DECIGO pathfinder (DPF) is the first milestone mission, and key components for DPF are being tested on ground and in orbit. In this paper, we review the conceptual design and current status of DECIGO and DPF.
Classical and Quantum Gravity 04/2010; 27(8):084010. · 3.32 Impact Factor
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ABSTRACT: Gravitational waves from coalescing compact binaries are one of the most promising sources for detectors such as LIGO, Virgo and GEO600. If the components of the binary posess significant angular momentum (spin), as is likely to be the case if one component is a black hole, spin-induced precession of a binary's orbital plane causes modulation of the gravitational-wave amplitude and phase. If the templates used in a matched-filter search do not accurately model these effects then the sensitivity, and hence the detection rate, will be reduced. We investigate the ability of several search pipelines to detect gravitational waves from compact binaries with spin. We use the post-Newtonian approximation to model the inspiral phase of the signal and construct two new template banks using the phenomenological waveforms of Buonanno, Chen and Vallisneri. We compare the performance of these template banks to that of banks constructed using the stationary phase approximation to the non-spinning post-Newtonian inspiral waveform currently used by LIGO and Virgo in the search for compact binary coalescence. We find that, at the same false alarm rate, a search pipeline using phenomenological templates is no more effective than a pipeline which uses non-spinning templates. We recommend the continued use of the non-spinning stationary phase template bank until the false alarm rate associated with templates which include spin effects can be substantially reduced. Comment: 11 pages, 3 figures
04/2009;
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Tomomi Akutsu,
Masaki Ando,
Tomiyoshi Haruyama,
Nobuyuki Kanda,
Kazuaki Kuroda,
Sinji Miyoki,
Masatake Ohashi,
Yoshio Saito,
Nobuaki Sato,
Takakazu Shintomi,
Toshikazu Suzuki,
Hideyuki Tagoshi, Hirotaka Takahashi,
Daisuke Tatsumi,
Souichi Telada,
Takayuki Tomaru,
Takashi Uchiyama,
Akira Yamamoto,
Kazuhiro Yamamoto
[show abstract]
[hide abstract]
ABSTRACT: We search for continuous gravitational waves from PSR J0835-4510 at twice its rotational frequency using CLIO (Cryogenic Laser Interferometric Observatory) in the Kamioka mine. In this search, we use data from an observational run during 12–28 February 2007. We give a brief description of the methods used in this search. We obtain an upper limit on gravitational wave amplitude for PSR J0835-4510 as h0(UL) = 5.3 × 10−20 with 99.4% confidence level.
Classical and Quantum Gravity 09/2008; 25(18):184013. · 3.32 Impact Factor
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ABSTRACT: We present the current state of veto studies in TAMA300 by monitor signals of the interferometer and its environment. In GW data analysis, fake GW events may bury real GW events or worse upper limits on the event rate. Thus, fake-event rejection is an important issue. In general, we can reject these fake events by the monitor signals, since these fake events are induced due to detector instabilities. However, using all monitor signals for the fake-event rejection would increase the accidental rejection probability and dead time without improving veto efficiency, since all monitor signals do not have correlations to the detector instabilities. Here, we analyze coincidences between the main and selected monitor signals with the optimal parameters for the fake-event rejection. Then, coincident events are rejected as the fake events. For the signal selection and parameter optimization, we systematically investigate the correlations with the detector instabilities. As a result, we achieved 30–99% veto efficiency using ten selected monitor signals with the 3.2% accidental rejection probability and 0.2% dead time.
Classical and Quantum Gravity 09/2007; 24(19):S405. · 3.32 Impact Factor
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ABSTRACT: We discuss the coherent search strategy to detect gravitational waves from inspiraling compact binaries by a network of correlated laser interferometric detectors. From the maximum likelihood ratio statistic, we obtain a coherent statistic which is slightly different from and generally better than what we obtained in our previous work. In the special case when the cross spectrum of two detectors normalized by the power spectrum density is constant, the new statistic agrees with the old one. The quantitative difference of the detection probability for a given false alarm rate is also evaluated in a simple case.
03/2007;
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ABSTRACT: We compare two strategies of multi-detector detection of compact binary inspiral signals, namely, the coincidence and the coherent. For simplicity we consider here two identical detectors having the same power spectral density of noise, that of initial LIGO, located in the same place and having the same orientation. We consider the cases of independent noise as well as that of correlated noise. The coincident strategy involves separately making two candidate event lists, one for each detector, and from these choosing those pairs of events from the two lists which lie within a suitable parameter window, which then are called as coincidence detections. The coherent strategy on the other hand involves combining the data phase coherently, so as to obtain a single network statistic which is then compared with a single threshold. Here we attempt to shed light on the question as to which strategy is better. We compare the performances of the two methods by plotting the Receiver Operating Characteristics (ROC) for the two strategies. Several of the results are obtained analytically in order to gain insight. Further we perform numerical simulations in order to determine certain parameters in the analytic formulae and thus obtain the final complete results. We consider here several cases from the relatively simple to the astrophysically more relevant in order to establish our results. The bottom line is that the coherent strategy although more computationally expensive in general than the coincidence strategy, is superior to the coincidence strategy - considerably less false dismissal probability for the same false alarm probability in the viable false alarm regime. Comment: 18 pages, 10 figures, typo corrected
08/2006;
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ABSTRACT: We present the status of the joint search for gravitational waves from inspiraling neutron star binaries in the LIGO Science Run 2 and TAMA300 Data Taking Run 8 data, which were taken from 14 February to 14 April 2003, by the LIGO and TAMA Collaborations. In this paper, we discuss what has been learned from an analysis of a subset of the data sample reserved as a 'playground'. We determine the coincidence conditions for parameters such as the coalescence time and chirp mass by injecting simulated Galactic binary neutron star signals into the data stream. We select coincidence conditions so as to maximize our efficiency of detecting simulated signals. We obtain an efficiency for our coincident search of 78% and show that we are missing primarily very distant signals for TAMA300. We perform a time-slide analysis to estimate the background due to accidental coincidence of noise triggers. We find that the background triggers have a very different character from the triggers of simulated signals.
Classical and Quantum Gravity 09/2005; 22(18):S1109. · 3.32 Impact Factor
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Masaki Ando,
Tomomi Akutsu,
Tomotada Akutsu,
Koji Arai,
Youichi Aso,
Mitsuhiro Fukushima,
Kazuhiro Hayama,
Nobuyuki Kanda,
Kazuhiro Kondo,
Norikatsu Mio, [......],
Shigeo Nagano,
Shuichi Sato,
Masaru Shibata,
Hideyuki Tagoshi, Hirotaka Takahashi,
Ryutaro Takahashi,
Daisuke Tatsumi,
Yoshiki Tsunesada,
Toshitaka Yamazaki,
the TAMA Collaboration
[show abstract]
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ABSTRACT: We present the results of observations with the TAMA300 gravitational-wave detector, targeting burst signals from stellar-core collapse events. We used an excess-power filter to extract gravitational-wave candidates, and developed two methods to reduce fake events caused by non-stationary noises of the detector. These analysis methods were applied to real data from the TAMA300 interferometric gravitational wave detector. We compared the data-processed results with those of a Monte Carlo simulation with an assumed galactic-event distribution model and with burst waveforms expected from numerical simulations of stellar-core collapses, in order to interpret the event candidates from an astronomical viewpoint. We set an upper limit of 5.0 × 103 events s−1 on the burst gravitational-wave event rate in our galaxy with a confidence level of 90%.
Classical and Quantum Gravity 09/2005; 22(18):S1283. · 3.32 Impact Factor
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ABSTRACT: Gravitational radiation from a slightly distorted black hole with ringdown waveform is well understood in general relativity. It provides a probe for direct observation of black holes and determination of their physical parameters, masses and angular momenta (Kerr parameters). For ringdown searches using data of gravitational wave detectors, matched filtering technique is useful. In this paper, we describe studies on problems in matched filtering analysis in realistic gravitational wave searches using observational data. Above all, we focus on template constructions, matches or signal-to-noise ratios (SNRs), detection probabilities for Galactic events, and accuracies in evaluation of waveform parameters or black hole hairs. In template design for matched filtering, search parameter ranges and template separations are determined by requirements from acceptable maximum loss of SNRs, detection efficiencies, and computational costs. In realistic searches using observational data, however, effects of nonstationary noises cause decreases of SNRs, and increases of errors in waveform parameter determinations. These problems will potentially arise in any matched filtering searches for any kind of waveforms. To investigate them, we have performed matched filtering analysis for artificial ringdown signals which are generated with Monte-Carlo technique and injected into the TAMA300 observational data. We employed an efficient method to construct a bank of ringdown filters recently proposed by Nakano et al., and use a template bank generated from a criterion such that losses of SNRs of any signals do not exceed 2%. We found that this criterion is fulfilled in ringdown searches using TAMA300 data, by examining distribution of SNRs of simulated signals. It is also shown that with TAMA300 sensitivity, the detection probability for Galactic ringdown events is about 50% for black holes of masses greater than 20M⊙ with SNR>10. The accuracies in waveform parameter estimations are found to be consistent with the template spacings, and resolutions for black hole masses and the Kerr parameters are evaluated as a few % and ∼40%, respectively. They can be improved up to <0.9% and <24% for events of SNR≥10 by using fine-meshed template bank in the hierarchical search strategy.
Phys. Rev. D. 05/2005; 71(10).
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[show abstract]
[hide abstract]
ABSTRACT: We present the status of the joint search for gravitational waves from inspiraling neutron star binaries in the LIGO Science Run 2 and TAMA300 Data Taking Run 8 data, which was taken from February 14 to April 14, 2003, by the LIGO and TAMA collaborations. In this paper we discuss what has been learned from an analysis of a subset of the data sample reserved as a ``playground''. We determine the coincidence conditions for parameters such as the coalescence time and chirp mass by injecting simulated Galactic binary neutron star signals into the data stream. We select coincidence conditions so as to maximize our efficiency of detecting simulated signals. We obtain an efficiency for our coincident search of 78 %, and show that we are missing primarily very distant signals for TAMA300. We perform a time slide analysis to estimate the background due to accidental coincidence of noise triggers. We find that the background triggers have a very different character from the triggers of simulated signals. Comment: 10 page, 8 figures, accepted for publication in Classical and Quantum Gravity for the special issue of the GWDAW9 Proceedings ; Corrected typos, minor changes
04/2005;
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Patrick J. Sutton,
Masaki Ando,
Patrick Brady,
Laura Cadonati,
Alessandra Di Credico,
Stephen Fairhurst,
Lee Samuel Finn,
Nobuyuki Kanda,
Erik Katsavounidis,
Sergey Klimenko, [......],
Szabolcs Marka,
John W. C. McNabb,
Saikat Ray Majumder,
Peter R. Saulson,
Hideyuki Tagoshi, Hirotaka Takahashi,
Ryutaro Takahashi,
Daisuke Tatsumi,
Yoshiki Tsunesada,
S. E. Whitcomb
[show abstract]
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ABSTRACT: We describe the plans for a joint search for unmodelled gravitational wave bursts being carried out by the LIGO and TAMA collaborations using data collected during February-April 2003. We take a conservative approach to detection, requiring candidate gravitational wave bursts to be seen in coincidence by all four interferometers. We focus on some of the complications of performing this coincidence analysis, in particular the effects of the different alignments and noise spectra of the interferometers.
01/2005;
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Masaki Ando,
Koji Arai,
Youichi Aso,
Peter Beyersdorf,
Kazuhiro Hayama,
Yukiyoshi Iida,
Nobuyuki Kanda,
Seiji Kawamura,
Kazuhiro Kondo,
Norikatsu Mio, [......],
Shigeo Nagano,
Kenji Numata,
Shuichi Sato,
Kentaro Somiya,
Hideyuki Tagoshi, Hirotaka Takahashi,
Ryutaro Takahashi,
Daisuke Tatsumi,
Yoshiki Tsunesada,
Zong-Hong Zhu
[show abstract]
[hide abstract]
ABSTRACT: We present data-analysis schemes and results of observations with the TAMA300 gravitational-wave detector, targeting burst signals from stellar-core collapse events. In analyses for burst gravitational waves, the detection and fake-reduction schemes are different from well-investigated ones for a chirp-wave analysis, because precise waveform templates are not available. We used an excess-power filter for the extraction of gravitational-wave candidates, and developed two methods for the reduction of fake events caused by non-stationary noises of the detector. These analysis schemes were applied to real data from the TAMA300 interferometric gravitational wave detector. As a result, fake events were reduced by a factor of about 1000 in the best cases. The resultant event candidates were interpreted from an astronomical viewpoint. We set an upper limit of 2.2x10^3 events/sec on the burst gravitational-wave event rate in our Galaxy with a confidence level of 90%. This work sets a milestone and prospects on the search for burst gravitational waves, by establishing an analysis scheme for the observation data from an interferometric gravitational wave detector.
11/2004;
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Hirotaka Takahashi,
Hideyuki Tagoshi,
Masaki Ando,
Koji Arai,
Peter Beyersdorf,
Nobuyuki Kanda,
Seiji Kawamura,
Norikatsu Mio,
Shinji Miyoki,
Shigenori Moriwaki, [......],
Ken-ichi Ueda,
Fumihiko Usui,
Koichi Waseda,
Yuko Watanabe,
Hiromi Yakura,
Kazuhiro Yamamoto,
Akira Yamamoto,
Toshitaka Yamazaki,
Tatsuo Yoda,
Zong-Hong Zhu
[show abstract]
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ABSTRACT: Japanese laser interferometric gravitational wave detectors, TAMA300 and LISM, performed a coincident observation during 2001. We perform a coincidence analysis to search for inspiraling compact binaries. The length of data used for the coincidence analysis is 275 hours when both TAMA300 and LISM detectors are operated simultaneously. TAMA300 and LISM data are analyzed by matched filtering, and candidates for gravitational wave events are obtained. If there is a true gravitational wave signal, it should appear in both data of detectors with consistent waveforms characterized by masses of stars, amplitude of the signal, the coalescence time and so on. We introduce a set of coincidence conditions of the parameters, and search for coincident events. This procedure reduces the number of fake events considerably, by a factor ∼10-4 compared with the number of fake events in single detector analysis. We find that the number of events after imposing the coincidence conditions is consistent with the number of accidental coincidences produced purely by noise. We thus find no evidence of gravitational wave signals. We obtain an upper limit of 0.046 [1/h] (C.L.=90%) to the galactic event rate within 1 kpc from the Earth. The method used in this paper can be applied straightforwardly to the case of coincidence observations with more than two detectors with arbitrary arm directions.
Phys. Rev. D. 08/2004; 70(4).
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[show abstract]
[hide abstract]
ABSTRACT: Japanese laser interferometric gravitational wave detectors, TAMA300 and LISM, performed a coincident observation during 2001. We perform a coincidence analysis to search for inspiraling compact binaries. The length of data used for the coincidence analysis is 275 hours when both TAMA300 and LISM detectors are operated simultaneously. TAMA300 and LISM data are analyzed by matched filtering, and candidates for gravitational wave events are obtained. If there is a true gravitational wave signal, it should appear in both data of detectors with consistent waveforms characterized by masses of stars, amplitude of the signal, the coalescence time and so on. We introduce a set of coincidence conditions of the parameters, and search for coincident events. This procedure reduces the number of fake events considerably, by a factor $\sim 10^{-4}$ compared with the number of fake events in single detector analysis. We find that the number of events after imposing the coincidence conditions is consistent with the number of accidental coincidences produced purely by noise. We thus find no evidence of gravitational wave signals. We obtain an upper limit of 0.046 /hours (CL $= 90 %$) to the Galactic event rate within 1kpc from the Earth. The method used in this paper can be applied straightforwardly to the case of coincidence observations with more than two detectors with arbitrary arm directions.
04/2004;
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ABSTRACT: A black hole has characteristic quasi-normal modes that will be excited when it is formed or when the geometry is perturbed. The state of a black hole when the quasi-normal modes are excited is called the gravitational ringing, and detections of it will be a direct confirmation of the existence of black holes. To detect it, a method based on matched filtering needs to be developed. Generically, matched filtering requires a large number of templates, because one has to ensure a proper match of a real gravitational wave with one of template waveforms to keep the detection efficiency as high as possible. On the other hand, the number of templates must be kept as small as possible under limited computational costs. In our previous paper, assuming that the gravitational ringing is dominated by the least-damped (fundamental) mode with the least imaginary part of frequency, we constructed an efficient method for tiling the template space. However, the dependence of the template space metric on the initial phase of a wave was not taken into account. This dependence arises because of an unavoidable mismatch between the parameters of a signal waveform and those given discretely in the template space. In this paper, we properly take this dependence into account and present an improved, efficient search method for gravitational ringing of black holes. Comment: 19 pages, 9 figures
03/2004;
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ABSTRACT: We present the preliminary results of the analysis to search for inspiraling compact binaries using TAMA300 DT8 data which was taken during 2003. We compare the quality and the stability of the data with that taken during DT6 in 2001. We find that the DT8 data has better quality and stability than the DT6 data. Comment: 6 pages, 4 figures,accepted for publication in Class. Quant. Grav. as Special issue article (Proceedings of the 5th Edoardo Amaldi Conference on Gravitational Waves, Tirrenia, Pisa, Italy, 6-11 July 2003)
11/2003;
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ABSTRACT: We discuss a method of coincidence analysis to search for gravitational waves from inspiralling compact binaries using the data of two laser interferometer gravitational wave detectors. We examine the allowed difference of the wave's parameters estimated by each detector to obtain good detection efficiency. We also discuss a method of setting an upper limit to the event rate from the results of the coincidence analysis. For the purpose of testing the above methods, we performed a coincidence analysis by applying these methods to the real data of TAMA300 and LISM detectors taken during 2001. We show that the fake event rate is reduced significantly by the coincidence analysis without losing real events very much. Results of the test analysis are also given.
Classical and Quantum Gravity 08/2003; 20(17):S741. · 3.32 Impact Factor
