DSpace Collection: Research Papers (TP)
http://hdl.handle.net/2289/144
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The third and a half post-Newtonian gravitational wave quadrupole mode for quasi-circular inspiralling compact binaries
http://hdl.handle.net/2289/6126
Title: The third and a half post-Newtonian gravitational wave quadrupole mode for quasi-circular inspiralling compact binaries<br/><br/>Authors: Faye, Guillaume; Marsat, Sylvain; Blanchet, Luc; Iyer, B.R.<br/><br/>Abstract: We compute the quadrupole mode of the gravitational waveform of inspiralling compact binaries at the third and half-post-Newtonian (3.5PN) approximation of general relativity. The computation is performed using the multipolar post-Newtonian formalism, and restricted to binaries without spins moving on quasi-circular orbits. The new inputs mainly include the 3.5PN terms in the mass quadrupole moment of the source, and the control of required subdominant corrections to the contributions of hereditary integrals (tails and nonlinear memory effect). The result is given in the form of the quadrupolar mode (2, 2) in a spin-weighted spherical harmonic decomposition of the waveform, and may be used for comparison with the counterpart quantity computed in numerical relativity. It is a step towards the computation of the full 3.5PN waveform, whose knowledge is expected to reduce the errors on the location parameters of the source.<br/><br/>Description: Restricted Access. An open-access version is available at arXiv.org (one of the alternative locations)Improved upper limits on the stochastic gravitational-wave background from 2009-2010 LIGO and Virgo Data
http://hdl.handle.net/2289/6090
Title: Improved upper limits on the stochastic gravitational-wave background from 2009-2010 LIGO and Virgo Data<br/><br/>Authors: Aasi, J.; Abbott, B.P.; Abbott, R.; Iyer, B.R.; LIGO Scientific Collaboration and Virgo Collaboration; +842 Co authors<br/><br/>Abstract: Gravitational waves from a variety of sources are predicted to superpose to create a stochastic background. This background is expected to contain unique information from throughout the history of the Universe that is unavailable through standard electromagnetic observations, making its study of fundamental importance to understanding the evolution of the Universe. We carry out a search for the stochastic background with the latest data from the LIGO and Virgo detectors. Consistent with predictions from most stochastic gravitational-wave background models, the data display no evidence of a stochastic gravitational-wave signal. Assuming a gravitational-wave spectrum of ΩGW(f)=Ωα(f/fref)α, we place 95% confidence level upper limits on the energy density of the background in each of four frequency bands spanning 41.5–1726 Hz. In the frequency band of 41.5–169.25 Hz for a spectral index of α=0, we constrain the energy density of the stochastic background to be ΩGW(f)<5.6×10−6. For the 600–1000 Hz band, ΩGW(f)<0.14(f/900 Hz)3, a factor of 2.5 lower than the best previously reported upper limits. We find ΩGW(f)<1.8×10−4 using a spectral index of zero for 170–600 Hz and ΩGW(f)<1.0(f/1300 Hz)3 for 1000–1726 Hz, bands in which no previous direct limits have been placed. The limits in these four bands are the lowest direct measurements to date on the stochastic background. We discuss the implications of these results in light of the recent claim by the BICEP2 experiment of the possible evidence for inflationary gravitational waves.<br/><br/>Description: Open AccessFirst all-sky search for continuous gravitational waves from unknown sources in binary systems
http://hdl.handle.net/2289/6089
Title: First all-sky search for continuous gravitational waves from unknown sources in binary systems<br/><br/>Authors: Aasi, J.; Abbott, B.P.; Abbott, R.; Abbott, T.; Iyer, B.R.; LIGO Scientific Collaboration and Virgo Collaboration; +842 Co authors<br/><br/>Abstract: We present the first results of an all-sky search for continuous gravitational waves from unknown spinning neutron stars in binary systems using LIGO and Virgo data. Using a specially developed analysis program, the TwoSpect algorithm, the search was carried out on data from the sixth LIGO science run and the second and third Virgo science runs. The search covers a range of frequencies from 20 Hz to 520 Hz, a range of orbital periods from 2 to ∼2,254 h and a frequency- and period-dependent range of frequency modulation depths from 0.277 to 100 mHz. This corresponds to a range of projected semimajor axes of the orbit from ∼0.6×10−3 ls to ∼6,500 ls assuming the orbit of the binary is circular. While no plausible candidate gravitational wave events survive the pipeline, upper limits are set on the analyzed data. The most sensitive 95% confidence upper limit obtained on gravitational wave strain is 2.3×10−24 at 217 Hz, assuming the source waves are circularly polarized. Although this search has been optimized for circular binary orbits, the upper limits obtained remain valid for orbital eccentricities as large as 0.9. In addition, upper limits are placed on continuous gravitational wave emission from the low-mass x-ray binary Scorpius X-1 between 20 Hz and 57.25 Hz.<br/><br/>Description: Open AccessConstraints on cosmic strings from the LIGO-Virgo gravitational-wave detectors
http://hdl.handle.net/2289/6028
Title: Constraints on cosmic strings from the LIGO-Virgo gravitational-wave detectors<br/><br/>Authors: Aasi, J.; Abadie, J.; Abbott, B.P.; Iyer, B.R.; LIGO Scientific Collaboration and Virgo Collaboration; +845 Co authors<br/><br/>Abstract: Cosmic strings can give rise to a large variety of interesting astrophysical phenomena. Among them, powerful bursts of gravitational waves (GWs) produced by cusps are a promising observational signature. In this Letter we present a search for GWs from cosmic string cusps in data collected by the LIGO and Virgo gravitational wave detectors between 2005 and 2010, with over 625 days of live time. We find no evidence of GW signals from cosmic strings. From this result, we derive new constraints on cosmic string parameters, which complement and improve existing limits from previous searches for a stochastic background of GWs from cosmic microwave background measurements and pulsar timing data. In particular, if the size of loops is given by the gravitational backreaction scale, we place upper limits on the string tension Gμ below 10−8 in some regions of the cosmic string parameter space.<br/><br/>Description: Open Access