We report the observation of a compact binary coalescence involving a 22.2 -
24.3 $M_{\odot}$ black hole and a compact object with a mass of 2.50 - 2.67
$M_{\odot}$ (all measurements quoted at the ...90$\%$ credible level). The
gravitational-wave signal, GW190814, was observed during LIGO's and Virgo's
third observing run on August 14, 2019 at 21:10:39 UTC and has a
signal-to-noise ratio of 25 in the three-detector network. The source was
localized to 18.5 deg$^2$ at a distance of $241^{+41}_{-45}$ Mpc; no
electromagnetic counterpart has been confirmed to date. The source has the most
unequal mass ratio yet measured with gravitational waves,
$0.112^{+0.008}_{-0.009}$, and its secondary component is either the lightest
black hole or the heaviest neutron star ever discovered in a double
compact-object system. The dimensionless spin of the primary black hole is
tightly constrained to $\leq 0.07$. Tests of general relativity reveal no
measurable deviations from the theory, and its prediction of higher-multipole
emission is confirmed at high confidence. We estimate a merger rate density of
1-23 Gpc$^{-3}$ yr$^{-1}$ for the new class of binary coalescence sources that
GW190814 represents. Astrophysical models predict that binaries with mass
ratios similar to this event can form through several channels, but are
unlikely to have formed in globular clusters. However, the combination of mass
ratio, component masses, and the inferred merger rate for this event challenges
all current models for the formation and mass distribution of compact-object
binaries.
Astrophysical Journal Letters 892 (2020) L3 On 2019 April 25, the LIGO Livingston detector observed a compact binary
coalescence with signal-to-noise ratio 12.9. The Virgo detector was also taking
...data that did not contribute to detection due to a low signal-to-noise ratio,
but were used for subsequent parameter estimation. The 90% credible intervals
for the component masses range from 1.12 to 2.52 $M_{\odot}$ (1.45 to 1.88
$M_{\odot}$ if we restrict the dimensionless component spin magnitudes to be
smaller than 0.05). These mass parameters are consistent with the individual
binary components being neutron stars. However, both the source-frame chirp
mass $1.44^{+0.02}_{-0.02} M_{\odot}$ and the total mass
$3.4^{+0.3}_{-0.1}\,M_{\odot}$ of this system are significantly larger than
those of any other known binary neutron star system. The possibility that one
or both binary components of the system are black holes cannot be ruled out
from gravitational-wave data. We discuss possible origins of the system based
on its inconsistency with the known Galactic binary neutron star population.
Under the assumption that the signal was produced by a binary neutron star
coalescence, the local rate of neutron star mergers is updated to $250-2810
\text{Gpc}^{-3}\text{yr}^{-1}$.
Summary The purpose of this study was to evaluate brachial artery blood flow changes during submaximal isometric contraction of the biceps and triceps brachii, in order to clarify the influence of ...the upper arm muscles activity on the local arterial flow. The brachial artery blood flow velocity and diameter were evaluated in twenty healthy men (mean age 29.6 years) at baseline (resting position) and during submaximal isometric contraction of the biceps and triceps brachii by means of ultrasonography (B-MODE and Doppler ultrasound methods). The brachial artery blood flow velocity was significantly higher than resting position during submaximal isometric contraction of the biceps ( P < 0.001) and triceps brachii ( P = 0.019). As to the brachial artery diameter, no significant change was observed during submaximal isometric contractions of the biceps and triceps brachii. Our preliminary findings suggest that the brachial artery blood flow velocity similarly increases during submaximal isometric contraction of the biceps and triceps brachii.
Abstract
The parallel usage of the two terms "alchemy" and "chemistry" by seventeenth-century writers has engendered considerable confusion among historians of science. Many historians have succumbed ...to the temptation of assuming that the early modern term "chemistry" referred to something like the modern discipline, while supposing that "alchemy" pertained to a different set of practices and beliefs, predominantly the art of transmuting base metals into gold. This paper provides the first exhaustive analysis of the two terms and their interlinguistic cognates in the seventeenth century. It demonstrates that the intentional partition of the two terms with the restriction of alchemy to the the sense of metallic transmutation was not widely accepted until the end of the seventeenth century, if even then. The major figure in the restriction of meaning, Nicolas Lemery, built on a spurious interpretation of the Arabic definite article al, which he inherited from earlier sources in the chemical textbook tradition. In order to curtail the tradition of anachronism and distortion engendered by the selective use of the terms "alchemy" and "chemistry" by historians, the authors conclude by suggesting a return to seventeenth-century terminology for discussing the different aspects of the early modern discipline "chymistry."
We present the results of a semicoherent search for continuous gravitational waves from the low-mass X-ray binary Scorpius X-1, using data from the first Advanced LIGO observing run. The search ...method uses details of the modelled, parametrized continuous signal to combine coherently data separated by less than a specified coherence time, which can be adjusted to trade off sensitivity against computational cost. A search was conducted over the frequency range from 25 Hz to 2000 Hz, spanning the current observationally-constrained range of the binary orbital parameters. No significant detection candidates were found, and frequency-dependent upper limits were set using a combination of sensitivity estimates and simulated signal injections. The most stringent upper limit was set at 175 Hz, with comparable limits set across the most sensitive frequency range from 100 Hz to 200 Hz. At this frequency, the 95 pct upper limit on signal amplitude h0 is 2.3e-25 marginalized over the unknown inclination angle of the neutron star's spin, and 8.03e-26 assuming the best orientation (which results in circularly polarized gravitational waves). These limits are a factor of 3-4 stronger than those set by other analyses of the same data, and a factor of about 7 stronger than the best upper limits set using initial LIGO data. In the vicinity of 100 Hz, the limits are a factor of between 1.2 and 3.5 above the predictions of the torque balance model, depending on inclination angle, if the most likely inclination angle of 44 degrees is assumed, they are within a factor of 1.7.
One unanswered question about the binary neutron star coalescence GW170817 is the nature of its post-merger remnant. A previous search for post-merger gravitational waves targeted high-frequency ...signals from a possible neutron star remnant with a maximum signal duration of 500 s. Here we revisit the neutron star remnant scenario with a focus on longer signal durations up until the end of the Second Advanced LIGO-Virgo Observing run, 8.5 days after the coalescence of GW170817. The main physical scenario for such emission is the power-law spindown of a massive magnetar-like remnant. We use four independent search algorithms with varying degrees of restrictiveness on the signal waveformand different ways of dealing with noise artefacts. In agreement with theoretical estimates, we find no significant signal candidates. Through simulated signals, we quantify that with the current detector sensitivity, nowhere in the studied parameter space are we sensitive to a signal from more than 1 Mpc away, compared to the actual distance of 40 Mpc. This study however serves as a prototype for post-merger analyses in future observing runs with expected higher sensitivity.
We present results from the first directed search for nontensorial gravitational waves. While general relativity allows for tensorial (plus and cross) modes only, a generic metric theory may, in ...principle, predict waves with up to six different polarizations. This analysis is sensitive to continuous signals of scalar, vector or tensor polarizations, and does not rely on any specific theory of gravity. After searching data from the first observation run of the advanced LIGO detectors for signals at twice the rotational frequency of 200 known pulsars, we find no evidence of gravitational waves of any polarization. We report the first upper limits for scalar and vector strains, finding values comparable in magnitude to previously-published limits for tensor strain. Our results may be translated into constraints on specific alternative theories of gravity.
The first observing run of Advanced LIGO spanned 4 months, from September 12, 2015 to January 19, 2016, during which gravitational waves were directly detected from two binary black hole systems, ...namely GW150914 and GW151226. Confident detection of gravitational waves requires an understanding of instrumental transients and artifacts that can reduce the sensitivity of a search. Studies of the quality of the detector data yield insights into the cause of instrumental artifacts and data quality vetoes specific to a search are produced to mitigate the effects of problematic data. In this paper, the systematic removal of noisy data from analysis time is shown to improve the sensitivity of searches for compact binary coalescences. The output of the PyCBC pipeline, which is a python-based code package used to search for gravitational wave signals from compact binary coalescences, is used as a metric for improvement. GW150914 was a loud enough signal that removing noisy data did not improve its significance. However, the removal of data with excess noise decreased the false alarm rate of GW151226 by more than two orders of magnitude, from 1 in 770 years to less than 1 in 186000 years.
The detection of gravitational waves with Advanced LIGO and Advanced Virgo has enabled novel tests of general relativity, including direct study of the polarization of gravitational waves. While ...general relativity allows for only two tensor gravitational-wave polarizations, general metric theories can additionally predict two vector and two scalar polarizations. The polarization of gravitational waves is encoded in the spectral shape of the stochastic gravitational-wave background, formed by the superposition of cosmological and individually-unresolved astrophysical sources. Using data recorded by Advanced LIGO during its first observing run, we search for a stochastic background of generically-polarized gravitational waves. We find no evidence for a background of any polarization, and place the first direct bounds on the contributions of vector and scalar polarizations to the stochastic background. Under log-uniform priors for the energy in each polarization, we limit the energy-densities of tensor, vector, and scalar modes at 95% credibility to \(\Omega^T_0 < 5.6 \times 10^{-8}\), \(\Omega^V_0 < 6.4\times 10^{-8}\), and \(\Omega^S_0 < 1.1\times 10^{-7}\) at a reference frequency \(f_0 = 25\) Hz.
