Source Confusion from Neutron Star Binaries in Ground-Based Gravitational Wave Detectors is Minimal

Upgrades beyond the current second generation of ground-based gravitational wave detectors will allow them to observe tens of thousands neutron star and black hole binaries. Given the typical minute-to-hour duration of neutron star signals in the detector frequency band, a number of them will overlap in the time-frequency plane resulting in a nonzero cross-correlation. We examine source confusion arising from overlapping signals whose time-frequency tracks cross. Adopting the median observed merger rate of $100$ Gpc$^{-3}$yr$^{-1}$, each neutron star binary signal overlaps with an average of 42(4)[0.5] other signals when observed from 2(5)[10] Hz. The vast majority of overlaps occur at low frequencies where the inspiral evolution is slow: 91% of time-frequency overlaps occur in band below 5 Hz. The combined effect of overlapping signals does not satisfy the central limit theorem and source confusion cannot be treated as stationary, Gaussian noise: on average 0.91(0.17)[0.05] signals are present in a single adaptive time-frequency bin centered at 2(5)[10] Hz. We quantify source confusion under a realistic neutron star binary population and find that parameter uncertainty typically increases by less than 1% unless there are overlapping signals whose detector-frame chirp mass difference is $\lesssim 0.01 M_{\odot}$ and the overlap frequency is $\gtrsim$ 40 Hz. Out of $1\times10^6$ simulated signals, 0.14% fall within this region of detector-frame chirp mass differences, but their overlap frequencies are typically lower than 40 Hz. Source confusion for ground-based detectors, where events overlap instantaneously is significantly milder than the equivalent LISA problem, where many classes of events overlap for the lifetime of the mission.Comment: 20 pages, 9 figures, 4 table

GATE : a simulation toolkit for PET and SPECT

Monte Carlo simulation is an essential tool in emission tomography that can assist in the design of new medical imaging devices, the optimization of acquisition protocols, and the development or assessment of image reconstruction algorithms and correction techniques. GATE, the Geant4 Application for Tomographic Emission, encapsulates the Geant4 libraries to achieve a modular, versatile, scripted simulation toolkit adapted to the field of nuclear medicine. In particular, GATE allows the description of time-dependent phenomena such as source or detector movement, and source decay kinetics. This feature makes it possible to simulate time curves under realistic acquisition conditions and to test dynamic reconstruction algorithms. A public release of GATE licensed under the GNU Lesser General Public License can be downloaded at the address http://www-lphe.epfl.ch/GATE/

Intra-Arterial Prostaglandin E1 Infusion in Patients with Rest Pain: Short-Term Results

Purpose. To present our results after short-term (1 month) intra-arterial infusion therapy of PGE1-alprostadil via a port system implanted in the ipsilateral external iliac artery (EIA) in patients with severe rest pain. Methods. Ten patients with severe rest pain were included. All patients showed extensive peripheral vascular disease below the knee. The tip of the catheter was introduced via a retrograde puncture in the ipsilateral external iliac artery (EIA). The patients received intraarterial infusion of PGE1, 20 mgr alprostadil daily, via the port catheter for 1 month. Results. Clinical success was evaluated according to subjective grading of pain (group A significant decrease, group B moderate decrease and group C no response). A significant decrease of rest pain was observed in 8 (group A, 80%) patients, a moderate decrease in 2 (Group B, 20%), whereas no patients demonstrated any significant response. Both patients of group B had Buergers' disease and continue to smoke during therapy. No peripheral thrombosis or clinical deterioration was noticed. Conclusion. Intraarterial infusion of PGE1 alprostadil on a daily basis, using a port catheter into the ipsilateral EIA, in selected patients with severe rest pain, seems to be very effective, without any serious complications

Detection and parameter estimation of binary neutron star merger remnants

Detection and parameter estimation of binary neutron star merger remnants can shed light on the physics of hot matter at supranuclear densities. Here we develop a fast, simple model that can generate gravitational waveforms, and show it can be used for both detection and parameter estimation of post-merger remnants. The model consists of three exponentially-damped sinusoids with a linear frequency-drift term. The median fitting factors between the model waveforms and numerical-relativity simulations exceed 0.90. We detect remnants at a post-merger signal-to-noise ratio of ≥7 using a Bayes-factor detection statistic with a threshold of 3000. We can constrain the primary post-merger frequency to ±^(1.4)_(1.2)% at post-merger signal-to-noise ratios of 15 with an increase in precision to ±^(0.3)_(0.2)% for post-merger signal-to-noise ratios of 50. The tidal coupling constant can be constrained to ±⁹₁₂% at post-merger signal-to-noise ratios of 15, and ±5% at post-merger signal-to-noise ratios of 50 using a hierarchical inference model

Detection and parameter estimation of binary neutron star merger remnants

Detection and parameter estimation of binary neutron star merger remnants can shed light on the physics of hot matter at supranuclear densities. Here we develop a fast, simple model that can generate gravitational waveforms, and show it can be used for both detection and parameter estimation of post-merger remnants. The model consists of three exponentially-damped sinusoids with a linear frequency-drift term. The median fitting factors between the model waveforms and numerical-relativity simulations exceed 0.90. We detect remnants at a post-merger signal-to-noise ratio of $\ge 7$ using a Bayes-factor detection statistic with a threshold of 3000. We can constrain the primary post-merger frequency to $\pm_{1.2}^{1.4}\%$ at post-merger signal-to-noise ratios of 15 with an increase in precision to $\pm_{0.2}^{0.3}\%$ for post-merger signal-to-noise ratios of 50. The tidal coupling constant can be constrained to $\pm^{9}_{12}\%$ at post-merger signal-to-noise ratios of 15, and $\pm 5\%$ at post-merger signal-to-noise ratios of 50 using a hierarchical inference model

First measurement of the Hubble Constant from a Dark Standard Siren using the Dark Energy Survey Galaxies and the LIGO/Virgo Binary–Black-hole Merger GW170814

International audienceWe present a multi-messenger measurement of the Hubble constant H 0 using the binary–black-hole merger GW170814 as a standard siren, combined with a photometric redshift catalog from the Dark Energy Survey (DES). The luminosity distance is obtained from the gravitational wave signal detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO)/Virgo Collaboration (LVC) on 2017 August 14, and the redshift information is provided by the DES Year 3 data. Black hole mergers such as GW170814 are expected to lack bright electromagnetic emission to uniquely identify their host galaxies and build an object-by-object Hubble diagram. However, they are suitable for a statistical measurement, provided that a galaxy catalog of adequate depth and redshift completion is available. Here we present the first Hubble parameter measurement using a black hole merger. Our analysis results in , which is consistent with both SN Ia and cosmic microwave background measurements of the Hubble constant. The quoted 68% credible region comprises 60% of the uniform prior range [20, 140] km s−1 Mpc−1, and it depends on the assumed prior range. If we take a broader prior of [10, 220] km s−1 Mpc−1, we find (57% of the prior range). Although a weak constraint on the Hubble constant from a single event is expected using the dark siren method, a multifold increase in the LVC event rate is anticipated in the coming years and combinations of many sirens will lead to improved constraints on H 0

GW170104: Observation of a 50-Solar-Mass Binary Black Hole Coalescence at Redshift 0.2

We describe the observation of GW170104, a gravitational-wave signal produced by the coalescence of a pair of stellar-mass black holes. The signal was measured on January 4, 2017 at 10: 11: 58.6 UTC by the twin advanced detectors of the Laser Interferometer Gravitational-Wave Observatory during their second observing run, with a network signal-to-noise ratio of 13 and a false alarm rate less than 1 in 70 000 years. The inferred component black hole masses are 31.2(-6.0)(+8.4)M-circle dot and 19.4(-5.9)(+5.3)M(circle dot) (at the 90% credible level). The black hole spins are best constrained through measurement of the effective inspiral spin parameter, a mass-weighted combination of the spin components perpendicular to the orbital plane, chi(eff) = -0.12(-0.30)(+0.21) . This result implies that spin configurations with both component spins positively aligned with the orbital angular momentum are disfavored. The source luminosity distance is 880(-390)(+450) Mpc corresponding to a redshift of z = 0.18(-0.07)(+0.08) . We constrain the magnitude of modifications to the gravitational-wave dispersion relation and perform null tests of general relativity. Assuming that gravitons are dispersed in vacuum like massive particles, we bound the graviton mass to m(g) <= 7.7 x 10(-23) eV/c(2). In all cases, we find that GW170104 is consistent with general relativity

Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta