63 research outputs found
Probing the Black Hole Metric. I. Black Hole Shadows and Binary Black-Hole Inspirals
In General Relativity, the spacetimes of black holes have three fundamental
properties: (i) they are the same, to lowest order in spin, as the metrics of
stellar objects; (ii) they are independent of mass, when expressed in geometric
units; and (iii) they are described by the Kerr metric. In this paper, we
quantify the upper bounds on potential black-hole metric deviations imposed by
observations of black-hole shadows and of binary black-hole inspirals in order
to explore the current experimental limits on possible violations of the last
two predictions. We find that both types of experiments provide correlated
constraints on deviation parameters that are primarily in the tt-components of
the spacetimes, when expressed in areal coordinates. We conclude that,
currently, there is no evidence for a deviations from the Kerr metric across
the 8 orders of magnitudes in masses and 16 orders in curvatures spanned by the
two types of black holes. Moreover, because of the particular masses of black
holes in the current sample of gravitational-wave sources, the correlations
imposed by the two experiments are aligned and of similar magnitudes when
expressed in terms of the far field, post-Newtonian predictions of the metrics.
If a future coalescing black-hole binary with two low-mass (e.g., ~3 Msun)
components is discovered, the degeneracy between the deviation parameters can
be broken by combining the inspiral constraints with those from the black-hole
shadow measurements.Comment: Physical Review D, submitte
Fortifying gravitational-wave tests of general relativity against astrophysical assumptions
Most tests of general relativity with gravitational-wave observations rely on
inferring the degree to which a signal deviates from general relativity in
conjunction with the astrophysical parameters of its source, such as the
component masses and spins of a compact binary. Due to features of the signal,
measurements of these deviations are often highly correlated with the
properties of astrophysical sources. As a consequence, prior assumptions about
astrophysical parameters will generally affect the inferred magnitude of the
deviations. Incorporating information about the underlying astrophysical
population is necessary to avoid biases in the inference of deviations from
general relativity. Current tests assume that the astrophysical population
follows an unrealistic fiducial prior chosen to ease sampling of the posterior
-- for example, a prior flat in component masses -- which is is inconsistent
with both astrophysical expectations and the distribution inferred from
observations. We propose a framework for fortifying tests of general relativity
by simultaneously inferring the astrophysical population using a catalog of
detections. Although this method applies broadly, we demonstrate it concretely
on massive graviton constraints and parameterized tests of deviations to the
post-Newtonian phase coefficients. Using observations from LIGO-Virgo-KAGRA's
third observing run, we show that concurrent inference of the astrophysical
distribution strengthens constraints and improves overall consistency with
general relativity. We provide updated constraints on deviations from the
theory, finding that, upon modeling the astrophysical population, the
90\%-credible upper limit on the mass of the graviton improves by to
and the inferred
population-level post-Newtonian deviations move closer to
zero.Comment: 20 pages, 11 figure
The imprint of superradiance on hierarchical black hole mergers
Ultralight bosons are a proposed solution to outstanding problems in
cosmology and particle physics: they provide a dark-matter candidate while
potentially explaining the strong charge-parity problem. If they exist,
ultralight bosons can interact with black holes through the superradiant
instability. In this work we explore the consequences of this instability on
the evolution of hierarchical black holes within dense stellar clusters. By
reducing the spin of individual black holes, superradiance reduce the recoil
velocity of merging binary black holes, which, in turn, increases the retention
fraction of hierarchical merger remnants. We show that the existence of
ultralight bosons with mass would lead to an increased rate of hierarchical black
hole mergers in nuclear star clusters. An ultralight boson in this energy range
would result in up to more present-day nuclear star clusters
supporting hierarchical growth. The presence of an ultralight boson can also
double the rate of intermediate mass black hole mergers to
\,Gpc\,yr in the local Universe. These results imply
that a select range of ultralight boson mass can have far-reaching consequences
for the population of black holes in dense stellar environments. Future studies
into black hole cluster populations and the spin distribution of hierarchically
formed black holes will test this scenario.Comment: 20 pages, 7 figure
Daviess County Hazardous Materials Commodity Flow Study
This report presents the results of a Hazardous Materials Commodity Flow Study for Daviess County, KY. Study components were conducted by Western Kentucky University in partnership with Daviess County Emergency Management Agency. The study area was focused in Daviess County and included a railway-monitoring site near Henderson, KY. A map of the Daviess County is shown in Figure 1.1. As part of this study, hazardous materials (hazmats) transported through the study area were monitored via placard surveys at the following sites: U.S. Highway 60 (Hwy 60), east and westbound lanes at East Fourth Street & the Hwy 60 Bypass (U.S. 231); U.S. Route 231 (Route 231), southbound lanes at East Fourth Street & and U.S. 231 South; William H. Natcher Parkway (Natcher Pkwy), north and southbound lanes at 4301 Plantation Pointe; Audubon Parkway, east and westbound lanes at second overpass west of Owensboro; CSX Railway (CSX), north and southbound trains monitored from Sunset Park in Henderson, KY while crossing over bridge between Kentucky and Indiana. The purpose of this report is to present information on patterns of hazardous materials commodity flow along Hwy 60, Hwy 231, Natcher Parkway, Audubon Parkway, and CSX, as observed from May 27, 2013 to August 7, 2013. This report also summarizes incidents involving hazardous materials over the previous 5 years, December 2008 to June 2013, in Daviess County
Gravitational-wave astronomy with a physical calibration model
We carry out astrophysical inference for compact binary merger events in LIGO-Virgo’s first gravitational-wave transient catalog (GWTC-1) using a physically motivated calibration model. We demonstrate that importance sampling can be used to reduce the cost of what would otherwise be a computationally challenging analysis for signal-to-noise ratios of current gravitational-wave detections. We show that including the physical estimate for the calibration error distribution has negligible impact on the inference of parameters for the events in GWTC-1. Studying a simulated signal with matched filter signal-to-noise ratio
SNR = 200, we project that a calibration error estimate typical of GWTC-1 is likely to be negligible for the current generation of gravitational-wave detectors. We argue that other sources of systematic error—from waveforms, prior distributions, and noise modeling—are likely to be more important. Finally, using the events in GWTC-1 as standard sirens, we infer an astrophysically informed improvement on the estimate of the calibration error in the LIGO interferometers
The curious case of GW200129: interplay between spin-precession inference and data-quality issues
Measurement of spin-precession in black hole binary mergers observed with
gravitational waves is an exciting milestone as it relates to both general
relativistic dynamics and astrophysical binary formation scenarios. In this
study, we revisit the evidence for spin-precession in GW200129 and localize its
origin to data in LIGO Livingston in the 20--50\,Hz frequency range where the
signal amplitude is lower than expected from a non-precessing binary given all
the other data. These data are subject to known data quality issues as a glitch
was subtracted from the detector's strain data. The lack of evidence for
spin-precession in LIGO Hanford leads to a noticeable inconsistency between the
inferred binary mass ratio and precessing spin in the two LIGO detectors,
something not expected from solely different Gaussian noise realizations. We
revisit the LIGO Livingston glitch mitigation and show that the difference
between a spin-precessing and a non-precessing interpretation for GW200129 is
smaller than the statistical and systematic uncertainty of the glitch
subtraction, finding that the support for spin-precession depends sensitively
on the glitch modeling. We also investigate the signal-to-noise ratio
trigger in the less sensitive Virgo detector. Though not influencing the
spin-precession studies, the Virgo trigger is grossly inconsistent with the
ones in LIGO Hanford and LIGO Livingston as it points to a much heavier system.
We interpret the Virgo data in the context of further data quality issues.
While our results do not disprove the presence of spin-precession in GW200129,
we argue that any such inference is contingent upon the statistical and
systematic uncertainty of the glitch mitigation. Our study highlights the role
of data quality investigations when inferring subtle effects such as
spin-precession for short signals such as the ones produced by high-mass
systems.Comment: 17 pages, 14 figures, 2 tables. Data release:
https://zenodo.org/record/725965
Removal of Fluoride from Mine Water via Adsorption for Land-Applied Soil Amendment
The team researched, designed, and economically analyzed a full-scale adsorption column system to be applied in mining processes that leave high amounts of fluoride in their effluent. This system was designed to remove fluoride from water saturated with calcium sulfate, as calcium sulfate is present in high amounts in certain mining processes. Currently, high density sludge (HDS) is commonly employed to reduce fluoride concentrations, but due to solubility limits the sludge treatment cannot lower fluoride below 10 mg/L (ppm). The current enforceable EPA standard for discharged water is at 4 mg/L (ppm), although mining companies anticipate that this standard will soon be lowered to 2 ppm. The team was tasked with designing a process to lower 10 ppm fluoride down to 2 ppm.
The team investigated various methods such as precipitation, ion exchange, and reverse osmosis to remove fluoride from the system. These methods were not cost-effective and did not produce environmentally friendly byproducts. The team ultimately presented the solution of bone char as an adsorbent, with a byproduct that can be safely applied as a soil amendment. A full-scale facility with two adsorption columns was designed to treat 1000 gpm of water
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