The hydraulic external pre-isolator (HEPI) is the first six degrees of freedom active seismic isolation system implemented at the Laser Interferometer Gravitational Wave Observatory (LIGO). ...Implementation was first completed at the LIGO Livingston Observatory (LLO) prior to LIGOʼs fifth science run7, successfully cutting down the disturbance seen by LLOʼs suspended optics in the two most prominent seismic disturbance bands, the microseism (0.1-0.3 Hz) and the anthropogenic (1-3 Hz) bands, by a factor of a few to tens. The improvement in seismic isolation contributed directly to LLOʼs much improved duty cycle of 66.7% and LIGOʼs triple coincident duty cycle of 53%. We report the design, control scheme, and isolation performance of HEPI at LLO in this paper. Aided by this success, funding for incorporating HEPI into the LIGO Hanford Observatory was approved and installation is currently underway.
The Laser Interferometer Gravitational Wave Observatory (LIGO) consists of two widely separated 4 km laser interferometers designed to detect gravitational waves from distant astrophysical sources in ...the frequency range from 10 Hz to 10 kHz. The first observation run of the Advanced LIGO detectors started in September 2015 and ended in January 2016. A strain sensitivity of better than 10 super(-23)/radicalHz was achieved around 100 Hz. Understanding both the fundamental and the technical noise sources was critical for increasing the astrophysical strain sensitivity. The average distance at which coalescing binary black hole systems with individual masses of 30Mmiddot could be detected above a signal-to-noise ratio (SNR) of 8 was 1.3 Gpc, and the range for binary neutron star inspirals was about 75 Mpc. With respect to the initial detectors, the observable volume of the Universe increased by a factor 69 and 43, respectively. These improvements helped Advanced LIGO to detect the gravitational wave signal from the binary black hole coalescence, known as GW150914.
We present direct upper limits on gravitational wave emission from the Crab pulsar using data from the first 9 months of the fifth science run of the Laser Interferometer Gravitational-wave ...Observatory (LIGO). These limits are based on two searches. In the first we assume that the gravitational wave emission follows the observed radio timing, giving an upper limit on gravitational wave emission that beats indirect limits inferred from the spin-down and braking index of the pulsar and the energetics of the nebula. In the second we allow for a small mismatch between the gravitational and radio signal frequencies and interpret our results in the context of two possible gravitational wave emission mechanisms.
We analyzed the available LIGO data coincident with GRB 070201, a short- duration, hard-spectrum -ray burst (GRB) whose electromagnetically determined sky position is coincident with the spiral arms ...of the Andromeda galaxy (M31). Possible progenitors of such short, hard GRBs include mergers of neutron stars or a neutron star and a black hole, or soft -ray repeater (SGR) flares. These events can be accompanied by gravitational-wave emission. No plausible gravitational-wave candidates were found within a 180 s long window around the time of GRB 070201. This result implies that a compact binary progenitor of GRB 070201, with masses in the range image and image, located in M31 is excluded at >99% confidence. If the GRB 070201 progenitor was not in M31, then we can exclude a binary neutron star merger progenitor with distance image Mpc, assuming random inclination, at 90% confidence. The result also implies that an unmodeled gravitational-wave burst from GRB 070201 most probably emitted less than image (image ergs) in any 100 ms long period within the signal region if the source was in M31 and radiated isotropically at the same frequency as LIGO's peak sensitivity (image Hz). This upper limit does not exclude current models of SGRs at the M31 distance.
We present results from an all-sky search for unmodeled gravitational-wave bursts in the data collected by the LIGO, GEO 600 and Virgo detectors between November 2006 and October 2007. The search is ...performed by three different analysis algorithms over the frequency band 50-6000 Hz. Data are analyzed for times with at least two of the four LIGO-Virgo detectors in coincident operation, with a total live time of 266 days. No events produced by the search algorithms survive the selection cuts. We set a frequentist upper limit on the rate of gravitational-wave bursts impinging on our network of detectors. When combined with the previous LIGO search of the data collected between November 2005 and November 2006, the upper limit on the rate of detectable gravitational-wave bursts in the 64-2048 Hz band is 2.0 events per year at 90% confidence. We also present event rate versus strength exclusion plots for several types of plausible burst waveforms. The sensitivity of the combined search is expressed in terms of the root-sum-squared strain amplitude for a variety of simulated waveforms and lies in the range 6×10-22 Hz-1/2 to 2×10-20 Hz-1/2. This is the first untriggered burst search to use data from the LIGO and Virgo detectors together, and the most sensitive untriggered burst search performed so far.
The Laser Interferometer Gravitational Wave Observatory (LIGO) is a network of three detectors built to detect local perturbations in the space–time metric from astrophysical sources. These ...detectors, two in Hanford, WA and one in Livingston, LA, are power-recycled Fabry-Perot Michelson interferometers. In their fifth science run (S5), between November 2005 and October 2007, these detectors accumulated one year of triple coincident data while operating at their designed sensitivity. In this paper, we describe the calibration of the instruments in the S5 data set, including measurement techniques and uncertainty estimation.
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