Numerical Relativity Injection Infrastructure

This document describes the new Numerical Relativity (NR) injection infrastructure in the LIGO Algorithms Library (LAL), which henceforth allows for the usage of NR waveforms as a discrete waveform approximant in LAL. With this new interface, NR waveforms provided in the described format can directly be used as simulated GW signals ("injections") for data analyses, which include parameter estimation, searches, hardware injections etc. As opposed to the previous infrastructure, this new interface natively handles sub-dominant modes and waveforms from numerical simulations of precessing binary black holes, making them directly accessible to LIGO analyses. To correctly handle precessing simulations, the new NR injection infrastructure internally transforms the NR data into the coordinate frame convention used in LAL.Comment: 20 pages, 2 figures, technical repor

Necessity of a Cardiopulmonary Resuscitation Refreshment Course Among Registered Nurses

Abstract Aims and objective: To (1) examine the level of comfort in performing CPR skills among registered nurses, and (2) assess the need for supplemental education between periods of recertification. Background: While Cardiopulmonary Resuscitation (CPR) and other Basic Life Support (BLS) skills are pivotal for patients experiencing life-threatening arrhythmias and cardiopulmonary arrest, there are limited studies assessing the comfort of registered nurses in performing these necessary skills. Design. A descriptive survey design was used to determine the comfort level of Registered Nurses performing CPR and perceived need for a CPR refresher course over the 24-month interval of CPR certification in registered nurses. Method: An online quantitative survey consisting of thirteen items was used to assess comfort, the need for supplemental education, and demographic variables in participating registered nurses. Results: Forty-one registered nurses (RNs) completed the online survey. Ninety percent (n=37) of the RNs responding indicated that they would feel comfortable performing CPR in an emergency situation, leaving 10% (n=4) of nurses who would not feel comfortable. Although the majority reported they would feel comfortable performing CPR, 63.2% (n=24) expressed an interest in taking a refresher course to improve their comfort. When asked about the motivation leading the need to refresh their CPR skills, 37.21% (n=16) reported due to a lack of practice, 30.23% (n=13) reported as the drive to become proficient, and 18.6% (n=8) because of their experience with witnessing/participation in cardiac arrest situations. Limitations: A small sample size (Comfort, n=41 & Need Assessment, n=24) and our tool of measurement was not previously validated. This can serve as a pilot for further research, although we would like to continue to have the survey open so as to increase the sample size and then recalculate and analyze the data. Conclusions. Ninety percent (90%) of registered nurses indicated that they felt comfortable in performing CPR, however, more than half expressed an interest in taking a refresher course to improve their comfort. Relevance to clinical practice. Providing frequent refresher courses between recertification periods is suggested as a way to increase the level of comfort among registered nurses in emergency situations where those skills are required. Key words: cardiopulmonary resuscitation, refresher course, comfort, need assessment, registered nurse

The End Of Nucleosynthesis: Production Of Lead And Thorium In The Early Galaxy

We examine the Pb and Th abundances in 27 metal-poor stars (-3.1 56) enrichment was produced only by the rapid (r-) nucleosynthesis process. New abundances are derived from Hubble Space Telescope/Space Telescope Imaging Spectrograph, Keck/High Resolution Echelle Spectrograph, and Very Large Telescope/UV-Visual Echelle Spectrograph spectra and combined with other measurements from the literature to form a more complete picture of nucleosynthesis of the heaviest elements produced in the r-process. In all cases, the abundance ratios among the rare earth elements and the third r-process peak elements considered (La, Eu, Er, Hf, and Ir) are constant and equivalent to the scaled solar system r-process abundance distribution. We compare the stellar observations with r-process calculations within the classical "waiting-point" approximation. In these computations a superposition of 15 weighted neutron-density components in the range 23 <= log n(n) <= 30 is fit to the r-process abundance peaks to successfully reproduce both the stable solar system isotopic distribution and the stable heavy element abundance pattern between Ba and U in low-metallicity stars. Under these astrophysical conditions, which are typical of the "main" r-process, we find very good agreement between the stellar Pb r-process abundances and those predicted by our model. For stars with anomalously high Th/Eu ratios (the so-called actinide boost), our observations demonstrate that any nucleosynthetic deviations from the main r-process affect-at most-only the elements beyond the third r-process peak, namely Pb, Th, and U. Our theoretical calculations also indicate that possible r-process abundance "losses" by nuclear fission are negligible for isotopes along the r-process path between Pb and the long-lived radioactive isotopes of Th and U.Deutsche Forschungsgemeinschaft KR 806/13-1Helmholtz Gemeinschaft VH-VI-061U S National Science Foundation AST 07-07447, AST 06-07708Astronom

Unequal Mass Binary Black Hole Plunges and Gravitational Recoil

We present results from fully nonlinear simulations of unequal mass binary black holes plunging from close separations well inside the innermost stable circular orbit with mass ratios q = M_1/M_2 = {1,0.85,0.78,0.55,0.32}, or equivalently, with reduced mass parameters $\eta=M_1M_2/(M_1+M_2)^2 = {0.25, 0.248, 0.246, 0.229, 0.183}$. For each case, the initial binary orbital parameters are chosen from the Cook-Baumgarte equal-mass ISCO configuration. We show waveforms of the dominant l=2,3 modes and compute estimates of energy and angular momentum radiated. For the plunges from the close separations considered, we measure kick velocities from gravitational radiation recoil in the range 25-82 km/s. Due to the initial close separations our kick velocity estimates should be understood as a lower bound. The close configurations considered are also likely to contain significant eccentricities influencing the recoil velocity.Comment: 12 pages, 5 figures, to appear in "New Frontiers" special issue of CQ

The PyCBC search for gravitational waves from compact binary coalescence

We describe the PyCBC search for gravitational waves from compact-object binary coalescences in advanced gravitational-wave detector data. The search was used in the first Advanced LIGO observing run and unambiguously identified two black hole binary mergers, GW150914 and GW151226. At its core, the PyCBC search performs a matched-filter search for binary merger signals using a bank of gravitational-wave template waveforms. We provide a complete description of the search pipeline including the steps used to mitigate the effects of noise transients in the data, identify candidate events and measure their statistical significance. The analysis is able to measure false-alarm rates as low as one per million years, required for confident detection of signals. Using data from initial LIGO's sixth science run, we show that the new analysis reduces the background noise in the search, giving a 30% increase in sensitive volume for binary neutron star systems over previous searches.Comment: 29 pages, 7 figures, accepted by Classical and Quantum Gravit

The Samurai Project: verifying the consistency of black-hole-binary waveforms for gravitational-wave detection

We quantify the consistency of numerical-relativity black-hole-binary waveforms for use in gravitational-wave (GW) searches with current and planned ground-based detectors. We compare previously published results for the $(\ell=2,| m | =2)$ mode of the gravitational waves from an equal-mass nonspinning binary, calculated by five numerical codes. We focus on the 1000M (about six orbits, or 12 GW cycles) before the peak of the GW amplitude and the subsequent ringdown. We find that the phase and amplitude agree within each code's uncertainty estimates. The mismatch between the $(\ell=2,| m| =2)$ modes is better than $10^{-3}$ for binary masses above $60 M_{\odot}$ with respect to the Enhanced LIGO detector noise curve, and for masses above $180 M_{\odot}$ with respect to Advanced LIGO, Virgo and Advanced Virgo. Between the waveforms with the best agreement, the mismatch is below $2 \times 10^{-4}$. We find that the waveforms would be indistinguishable in all ground-based detectors (and for the masses we consider) if detected with a signal-to-noise ratio of less than $\approx14$, or less than $\approx25$ in the best cases.Comment: 17 pages, 9 figures. Version accepted by PR

The SXS Collaboration catalog of binary black hole simulations

Accurate models of gravitational waves from merging black holes are necessary for detectors to observe as many events as possible while extracting the maximum science. Near the time of merger, the gravitational waves from merging black holes can be computed only using numerical relativity. In this paper, we present a major update of the Simulating eXtreme Spacetimes (SXS) Collaboration catalog of numerical simulations for merging black holes. The catalog contains 2018 distinct configurations (a factor of 11 increase compared to the 2013 SXS catalog), including 1426 spin-precessing configurations, with mass ratios between 1 and 10, and spin magnitudes up to 0.998. The median length of a waveform in the catalog is 39 cycles of the dominant $\ell=m=2$ gravitational-wave mode, with the shortest waveform containing 7.0 cycles and the longest 351.3 cycles. We discuss improvements such as correcting for moving centers of mass and extended coverage of the parameter space. We also present a thorough analysis of numerical errors, finding typical truncation errors corresponding to a waveform mismatch of $\sim 10^{-4}$. The simulations provide remnant masses and spins with uncertainties of 0.03% and 0.1% ($90^{\text{th}}$ percentile), about an order of magnitude better than analytical models for remnant properties. The full catalog is publicly available at https://www.black-holes.org/waveforms .Comment: 33+18 pages, 13 figures, 4 tables, 2,018 binaries. Catalog metadata in ancillary JSON file. v2: Matches version accepted by CQG. Catalog available at https://www.black-holes.org/waveform

Error-analysis and comparison to analytical models of numerical waveforms produced by the NRAR Collaboration

The Numerical-Relativity-Analytical-Relativity (NRAR) collaboration is a joint effort between members of the numerical relativity, analytical relativity and gravitational-wave data analysis communities. The goal of the NRAR collaboration is to produce numerical-relativity simulations of compact binaries and use them to develop accurate analytical templates for the LIGO/Virgo Collaboration to use in detecting gravitational-wave signals and extracting astrophysical information from them. We describe the results of the first stage of the NRAR project, which focused on producing an initial set of numerical waveforms from binary black holes with moderate mass ratios and spins, as well as one non-spinning binary configuration which has a mass ratio of 10. All of the numerical waveforms are analysed in a uniform and consistent manner, with numerical errors evaluated using an analysis code created by members of the NRAR collaboration. We compare previously-calibrated, non-precessing analytical waveforms, notably the effective-one-body (EOB) and phenomenological template families, to the newly-produced numerical waveforms. We find that when the binary's total mass is ~100-200 solar masses, current EOB and phenomenological models of spinning, non-precessing binary waveforms have overlaps above 99% (for advanced LIGO) with all of the non-precessing-binary numerical waveforms with mass ratios <= 4, when maximizing over binary parameters. This implies that the loss of event rate due to modelling error is below 3%. Moreover, the non-spinning EOB waveforms previously calibrated to five non-spinning waveforms with mass ratio smaller than 6 have overlaps above 99.7% with the numerical waveform with a mass ratio of 10, without even maximizing on the binary parameters.Comment: 51 pages, 10 figures; published versio