Observation of a potential future sensitivity limitation from ground motion at LIGO Hanford

A first detection of terrestrial gravity noise in gravitational-wave detectors is a formidable challenge. With the help of environmental sensors, it can in principle be achieved before the noise becomes dominant by estimating correlations between environmental sensors and the detector. The main complication is to disentangle different coupling mechanisms between the environment and the detector. In this paper, we analyze the relations between physical couplings and correlations that involve ground motion and LIGO strain data h(t) recorded during its second science run in 2016 and 2017. We find that all noise correlated with ground motion was more than an order of magnitude lower than dominant low-frequency instrument noise, and the dominant coupling over part of the spectrum between ground and h(t) was residual coupling through the seismic-isolation system. We also present the most accurate gravitational coupling model so far based on a detailed analysis of data from a seismic array. Despite our best efforts, we were not able to unambiguously identify gravitational coupling in the data, but our improved models confirm previous predictions that gravitational coupling might already dominate linear ground-to-h(t) coupling over parts of the low-frequency, gravitational-wave observation band

Short-term post release mortality of skates (family Rajidae) discarded in a western North Atlantic commercial otter trawl fishery

a b s t r a c t Due to market and regulatory factors, Rajidae skates are routinely discarded by commercial otter trawlers in the western North Atlantic. Accounting for post-release mortality is therefore essential to total fishing mortality estimates, stock status and management of this group of fishes. However, despite a presumed species-specific range in tolerance, few studies have investigated the short-term post-release mortality among skates indigenous to the western North Atlantic following capture by mobile fishing gears, and never in the Gulf of Maine. This study addresses this shortfall for the prohibited thorny skate, Amblyraja radiate and smooth skate, Malacoraja senta, and the targeted winter skate, Leucoraja ocellata, and little skate, Leucoraja erinacea. Of 1288 skates evaluated, negligible immediate mortality was observed at the time of capture, even in relation to the largest catches and/or most prolonged tows. However, injury frequency was moderate, with highest levels in the smooth (60%) and thorny (52%) skates. Aside from the smooth skate (59%), 72 h mortality rates were low overall (19% across all species when accounting tow durations indicative of the fishery), with the winter skate (8%) exhibiting the lowest levels. Logistic regression modeling revealed tow duration as the most universal predictor of condition and 72 h mortality, while catch biomass, sex, temperature changes, and animal size also held influence in certain species. Although in general the studied species appear more resilient to trawl capture and handling than previously estimated, interspecific differences must be accounted for when managing this group

Implications of Dedicated Seismometer Measurements on Newtonian-Noise Cancellation for Advanced LIGO

Newtonian gravitational noise from seismic fields will become a limiting noise source at low frequency for second-generation, gravitational-wave detectors. It is planned to use seismic sensors surrounding the detectors’ test masses to coherently subtract Newtonian noise using Wiener filters derived from the correlations between the sensors and detector data. In this Letter, we use data from a seismometer array deployed at the corner station of the Laser Interferometer Gravitational Wave Observatory (LIGO) Hanford detector combined with a tiltmeter for a detailed characterization of the seismic field and to predict achievable Newtonian-noise subtraction levels. As was shown previously, cancellation of the tiltmeter signal using seismometer data serves as the best available proxy of Newtonian-noise cancellation. According to our results, a relatively small number of seismometers is likely sufficient to perform the noise cancellation due to an almost ideal two-point spatial correlation of seismic surface displacement at the corner station, or alternatively, a tiltmeter deployed under each of the two test masses of the corner station at Hanford will be able to efficiently cancel Newtonian noise. Furthermore, we show that the ground tilt to differential arm-length coupling observed during LIGO’s second science run is consistent with gravitational coupling

Search for gravitational waves from low mass compact binary coalescence in LIGO’s sixth science run and Virgo’s science runs 2 and 3

We report on a search for gravitational waves from coalescing compact binaries using LIGO and Virgo observations between July 7, 2009, and October 20, 2010. We searched for signals from binaries with total mass between 2 and 25M_⊙; this includes binary neutron stars, binary black holes, and binaries consisting of a black hole and neutron star. The detectors were sensitive to systems up to 40 Mpc distant for binary neutron stars, and further for higher mass systems. No gravitational-wave signals were detected. We report upper limits on the rate of compact binary coalescence as a function of total mass, including the results from previous LIGO and Virgo observations. The cumulative 90% confidence rate upper limits of the binary coalescence of binary neutron star, neutron star-black hole, and binary black hole systems are 1.3×10^(-4), 3.1×10^(-5), and 6.4×10^(-6)  Mpc^(-3) yr^(-1), respectively. These upper limits are up to a factor 1.4 lower than previously derived limits. We also report on results from a blind injection challenge