10 research outputs found
Integration and Performance of the Newtonian Calibrator and IWAVE for Exploring the Laser Interferometer Gravitational Wave Observatory Data.
Upgrades to IWAVE, a frequency tracking tool invented by Edward J. Daw
at the University of Sheffield, has expanded the utility of the tool. Resonant
characteristics observed in the Laser Interferometer Gravitational Wave Observa-
tories - such as violin modes, test mass body modes and calibration signals - can
be resolved accurately, even in tightly packed regions of frequency space using a
multi-line tracker in real-time on the LIGO front end.
Furthermore, using IWAVE to develop test mass thermometers, real-time esti-
mates of the test mass temperature is available, useful for thermal tuning of LIGO.
This is achieved by tracking and calibrating test mass body modes, a coupling be-
tween the laser TEM modes and the mechanical response of the optics. The test
mass thermometers can be extrapolated into a larger thermal monitoring pipeline
useful for current and future gravitation wave observatory thermal modelling.
The LIGO calibration is a complicated folding of the many control systems
noise sources that affect the interferometer. Presented here is the installation,
commissioning and successful operation of the LIGO Hanford Newtonian Calibra-
tor - a new R&D effort with the University of Washington that uses a spinning
constellation of masses - to induce length changes in the interferometer arms by
applying a small force to the test mass. These forces are modelled with three real-
isations of Newton Law of Gravity and all show good agreement to one another
Initial Results from the LIGO Newtonian Calibrator
The precise calibration of the strain readout of the LIGO gravitational wave
observatories is paramount to the accurate interpretation of gravitational wave
events. This calibration is traditionally done by imparting a known force on
the test masses of the observatory via radiation pressure. Here we describe the
implementation of an alternative calibration scheme: the Newtonian Calibrator.
This system uses a rotor consisting of both quadrupole and hexapole mass
distributions to apply a time-varying gravitational force on one of the
observatory's test masses. The force produced by this rotor can be predicted to
relative uncertainty and is well-resolved in the readout of the
observatory. This system currently acts as a cross-check of the existing
absolute calibration system
Characterization of systematic error in Advanced LIGO calibration
The raw outputs of the detectors within the Advanced Laser Interferometer
Gravitational-Wave Observatory need to be calibrated in order to produce the
estimate of the dimensionless strain used for astrophysical analyses. The two
detectors have been upgraded since the second observing run and finished the
year-long third observing run. Understanding, accounting, and/or compensating
for the complex-valued response of each part of the upgraded detectors improves
the overall accuracy of the estimated detector response to gravitational waves.
We describe improved understanding and methods used to quantify the response of
each detector, with a dedicated effort to define all places where systematic
error plays a role. We use the detectors as they stand in the first half (six
months) of the third observing run to demonstrate how each identified
systematic error impacts the estimated strain and constrain the statistical
uncertainty therein. For this time period, we estimate the upper limit on
systematic error and associated uncertainty to be in magnitude and deg in phase ( confidence interval) in the most sensitive frequency
band 20-2000 Hz. The systematic error alone is estimated at levels of
in magnitude and deg in phase
Point absorbers in Advanced LIGO
Small, highly absorbing points are randomly present on the surfaces of the
main interferometer optics in Advanced LIGO. The resulting nano-meter scale
thermo-elastic deformations and substrate lenses from these micron-scale
absorbers significantly reduces the sensitivity of the interferometer directly
though a reduction in the power-recycling gain and indirect interactions with
the feedback control system. We review the expected surface deformation from
point absorbers and provide a pedagogical description of the impact on power
build-up in second generation gravitational wave detectors (dual-recycled
Fabry-Perot Michelson interferometers). This analysis predicts that the
power-dependent reduction in interferometer performance will significantly
degrade maximum stored power by up to 50% and hence, limit GW sensitivity, but
suggests system wide corrections that can be implemented in current and future
GW detectors. This is particularly pressing given that future GW detectors call
for an order of magnitude more stored power than currently used in Advanced
LIGO in Observing Run 3. We briefly review strategies to mitigate the effects
of point absorbers in current and future GW wave detectors to maximize the
success of these enterprises.Comment: 49 pages, 16 figures. -V2: typographical errors in equations B9 and
B10 were corrected (stray exponent of "h" was removed). Caption of Figure 9
was corrected to indicate that 40mW was used for absorption in the model, not
10mW as incorrectly indicated in V
Open data from the first and second observing runs of Advanced LIGO and Advanced Virgo
Advanced LIGO and Advanced Virgo are monitoring the sky and collecting gravitational-wave strain data with sufficient sensitivity to detect signals routinely. In this paper we describe the data recorded by these instruments during their first and second observing runs. The main data products are gravitational-wave strain time series sampled at 16384 Hz. The datasets that include this strain measurement can be freely accessed through the Gravitational Wave Open Science Center at http://gw-openscience.org, together with data-quality information essential for the analysis of LIGO and Virgo data, documentation, tutorials, and supporting software
Search for intermediate-mass black hole binaries in the third observing run of Advanced LIGO and Advanced Virgo
International audienceIntermediate-mass black holes (IMBHs) span the approximate mass range 100â105âMâ, between black holes (BHs) that formed by stellar collapse and the supermassive BHs at the centers of galaxies. Mergers of IMBH binaries are the most energetic gravitational-wave sources accessible by the terrestrial detector network. Searches of the first two observing runs of Advanced LIGO and Advanced Virgo did not yield any significant IMBH binary signals. In the third observing run (O3), the increased network sensitivity enabled the detection of GW190521, a signal consistent with a binary merger of mass âŒ150âMâ providing direct evidence of IMBH formation. Here, we report on a dedicated search of O3 data for further IMBH binary mergers, combining both modeled (matched filter) and model-independent search methods. We find some marginal candidates, but none are sufficiently significant to indicate detection of further IMBH mergers. We quantify the sensitivity of the individual search methods and of the combined search using a suite of IMBH binary signals obtained via numerical relativity, including the effects of spins misaligned with the binary orbital axis, and present the resulting upper limits on astrophysical merger rates. Our most stringent limit is for equal mass and aligned spin BH binary of total mass 200âMâ and effective aligned spin 0.8 at 0.056 Gpcâ3 yrâ1 (90% confidence), a factor of 3.5 more constraining than previous LIGO-Virgo limits. We also update the estimated rate of mergers similar to GW190521 to 0.08 Gpcâ3 yrâ1.Key words: gravitational waves / stars: black holes / black hole physicsCorresponding author: W. Del Pozzo, e-mail: [email protected]â Deceased, August 2020