10 research outputs found
Observation of a kilogram-scale oscillator near its quantum ground state
We introduce a novel cooling technique capable of approaching the quantum ground state of a kilogram-scale systemâan interferometric gravitational wave detector. The detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) operate within a factor of 10 of the standard quantum limit (SQL), providing a displacement sensitivity of 10â18 m in a 100 Hz band centered on 150 Hz. With a new feedback strategy, we dynamically shift the resonant frequency of a 2.7 kg pendulum mode to lie within this optimal band, where its effective temperature falls as low as 1.4 ÎŒK, and its occupation number reaches about 200 quanta. This work shows how the exquisite sensitivity necessary to detect gravitational waves can be made available to probe the validity of quantum mechanics on an enormous mass scale
First cross-correlation analysis of interferometric and resonant-bar gravitational-wave data for stochastic backgrounds (vol 76, art no 022001, 2007)
Data from the LIGO Livingston interferometer and the ALLEGRO resonant-bar detector, taken during LIGOâs fourth science run, were examined for cross correlations indicative of a stochastic gravitational-wave background in the frequency range 850â950 Hz, with most of the sensitivity arising between 905 and 925 Hz. ALLEGRO was operated in three different orientations during the experiment to modulate the relative sign of gravitational-wave and environmental correlations. No statistically significant correlations were seen in any of the orientations, and the results were used to set a Bayesian 90% confidence level upper limit of Ωgw(f)â€1.02, which corresponds to a gravitational-wave strain at 915 Hz of 1.5Ă10-23 Hz-1/2. In the traditional units of h1002Ωgw(f), this is a limit of 0.53, 2 orders of magnitude better than the previous direct limit at these frequencies. The method was also validated with successful extraction of simulated signals injected in hardware and software
An upper limit on the stochastic gravitational-wave background of cosmological origin
A stochastic background of gravitational waves is expected to arise from a superposition of a large number of unresolved gravitational-wave sources of astrophysical and cosmological origin. It should carry unique signatures from the earliest epochs in the evolution of the Universe, inaccessible to standard astrophysical observations1. Direct measurements of the amplitude of this background are therefore of fundamental importance for understanding the evolution of the Universe when it was younger than one minute. Here we report limits on the amplitude of the stochastic gravitational-wave background using the data from a two-year science run of the Laser Interferometer Gravitational-wave Observatory2 (LIGO). Our result constrains the energy density of the stochastic gravitational-wave background normalized by the critical energy density of the Universe, in the frequency band around 100 Hz, to be <6.9 10-6 at 95% confidence. The data rule out models of early Universe evolution with relatively large equation-of-state parameter3, as well as cosmic (super)string models with relatively small string tension4 that are favoured in some string theory models5. This search for the stochastic background improves on the indirect limits from Big Bang nucleosynthesis1, 6 and cosmic microwave background7 at 100 Hz
SEARCH FOR GRAVITATIONAL-WAVE BURSTS ASSOCIATED WITH GAMMA-RAY BURSTS USING DATA FROM LIGO SCIENCE RUN 5 AND VIRGO SCIENCE RUN 1
We present the results of a search for gravitational-wave bursts associated
with 137 gamma-ray bursts (GRBs) that were detected by satellite-based
gamma-ray experiments during the fifth LIGO science run and first Virgo science
run. The data used in this analysis were collected from 2005 November 4 to 2007
October 1, and most of the GRB triggers were from the Swift satellite. The
search uses a coherent network analysis method that takes into account the
different locations and orientations of the interferometers at the three
LIGO-Virgo sites. We find no evidence for gravitational-wave burst signals
associated with this sample of GRBs. Using simulated short-duration (<1 s)
waveforms, we set upper limits on the amplitude of gravitational waves
associated with each GRB. We also place lower bounds on the distance to each
GRB under the assumption of a fixed energy emission in gravitational waves,
with typical limits of D ~ 15 Mpc (E_GW^iso / 0.01 M_o c^2)^1/2 for emission at
frequencies around 150 Hz, where the LIGO-Virgo detector network has best
sensitivity. We present astrophysical interpretations and implications of these
results, and prospects for corresponding searches during future LIGO-Virgo
runs.Comment: 16 pages, 3 figures. Updated references. To appear in ApJ
Search for gravitational waves from binary black hole inspiral, merger, and ringdown
We present the first modeled search for gravitational waves using the complete binary black-hole gravitational waveform from inspiral through the merger and ringdown for binaries with negligible component spin. We searched approximately 2 years of LIGO data, taken between November 2005 and September 2007, for systems with component masses of 1â99Mâ and total masses of 25â100Mâ. We did not detect any plausible gravitational-wave signals but we do place upper limits on the merger rate of binary black holes as a function of the component masses in this range. We constrain the rate of mergers for 19Mââ€m1, m2â€28Mâ binary black-hole systems with negligible spin to be no more than 2.0ââMpcâ3âMyrâ1 at 90% confidence