About the detection of gravitational wave bursts

Several filtering methods for the detection of gravitational wave bursts in interferometric detectors are presented. These are simple and fast methods which can act as online triggers. All methods are compared to matched filtering with the help of a figure of merit based on the detection of supernovae signals simulated by Zwerger and Muller.Comment: 5 pages, proceedings of GWDAW99 (Roma, Dec. 1999), to appear in Int. J. Mod. Phys.

An efficient filter for detecting gravitational wave bursts in interferometric detectors

Typical sources of gravitational wave bursts are supernovae, for which no accurate models exist. This calls for search methods with high efficiency and robustness to be used in the data analysis of foreseen interferometric detectors. A set of such filters is designed to detect gravitational wave burst signals. We first present filters based on the linear fit of whitened data to short straight lines in a given time window and combine them in a non linear filter named ALF. We study the performances and efficiencies of these filters, with the help of a catalogue of simulated supernova signals. The ALF filter is the most performant and most efficient of all filters. Its performance reaches about 80% of the Optimal Filter performance designed for the same signals. Such a filter could be implemented as an online trigger (dedicated to detect bursts of unknown waveform) in interferometric detectors of gravitational waves

Egc: A Time-Frequency Augmented Template-Based Method For Gravitational Wave Burst Search In Ground-Based Interferometers

The detection of burst-type events in the output of ground gravitational wave detectors is particularly challenging. The potential variety of astrophysical waveforms, as proposed by simulations and analytic studies in general relativity and the discrimination of actual signals from instrumental noise both are critical issues. Robust methods that achieve reasonable detection performances over a wide range of signals are required. We present here a hybrid burst-detection pipeline related to time–frequency transforms while based on matched filtering to provide robustness against noise characteristics. Studies on simulated noise show that the algorithm has a detection efficiency similar to other methods over very different waveforms and particularly good timing even for low amplitude signals: no bias for most tested waveforms and an average accuracy of 1.1 ms (down to 0.1 ms in the best case). Time–frequency-type parameters, useful for event classification, are also derived for noise spectral densities unfavourable to standard time–frequency algorithms

Prescribing pathways to triple therapy: a multi-country, retrospective observational study of adult patients with chronic obstructive pulmonary disease

Introduction Maintenance treatment strategies in COPD recommend inhaled corticosteroid (ICS) + long-acting muscarinic antagonist (LAMA) + long-acting β2-agonist (LABA) triple therapy after initial dual therapy. Little is known about how treatment pathways to triple therapy vary across countries in clinical practice. Methods This multi-country, retrospective cohort study (conducted 1 January 2005–1 May 2016) included patients with a COPD diagnosis, and (UK only) evidence of smoking history, or (France, Italy, Germany, and Australia) an indicator confirming COPD diagnosis, a first instance of triple therapy recorded during the study period and ≥ 12 months of data prior to this date. Treatment pathways to triple therapy were analyzed in patients whose first instance of triple therapy was on or after the initial COPD diagnosis. The proportion of patients who initiated triple therapy prior to initial COPD diagnosis was also estimated. Meta-analyses of the main results were performed. Results In 130,729 patients across all countries, mean age (standard deviation) ranged from 63.4 (10.4) years (Germany) to 69.8 (9.9) years (Italy), and median time (interquartile range) from initial COPD diagnosis to first prescription of triple therapy ranged from 16.9 (5.7–36.2) months (Australia) to 42.5 (13.9–87.4) months (UK). ICS + LABA was the most common treatment pathway prior to triple therapy in the UK, Germany, and Italy (27.3%–31.6%); no previous maintenance therapy prior to triple therapy was the most common pathway in France and Australia (32.5% and 37.9%, respectively). Meta-analyses provided a pooled estimate of 20.4% (95% confidence interval: 13.8%–29.1%) for the proportion of patients initiating triple therapy at or before initial COPD diagnosis. Conclusions In this retrospective cohort study, treatment pathways to triple therapy were diverse within and between countries. The differing impact of treatments may affect quality of life and disease control in patients with COPD. Further analyses should investigate factors influencing pathways to triple therapy

A First Comparison Between LIGO and Virgo Inspiral Search Pipelines

This article reports on a project that is the first step the LIGO Scientific Collaboration and the Virgo Collaboration have taken to prepare for the mutual search for inspiral signals. The project involved comparing the analysis pipelines of the two collaborations on data sets prepared by both sides, containing simulated noise and injected events. The ability of the pipelines to detect the injected events was checked, and a first comparison of how the parameters of the events were recovered has been completed.Comment: GWDAW-9 proceeding

Inference of proto-neutron star properties in core-collapse supernovae from a gravitational-wave detector network

The next Galactic core-collapse supernova (CCSN) will be a unique opportunity to study within a fully multi-messenger approach the explosion mechanism responsible for the formation of neutron stars and stellar-mass black holes. State-of-the-art numerical simulations of those events reveal the complexity of the gravitational-wave emission which is highly stochastic. This challenges the possibility to infer the properties of the compact remnant and of its progenitor using the information encoded in the waveforms. In this paper we take further steps in a program we recently initiated to overcome those difficulties. In particular we show how oscillation modes of the proto-neutron star, highly visible in the gravitational-wave signal, can be used to reconstruct the time evolution of their physical properties. Extending our previous work where only the information from a single detector was used we here describe a new data-analysis pipeline that coherently combines gravitational-wave detectors' data and infers the time evolution of a combination of the mass and radius of the compact remnant. The performance of the method is estimated employing waveforms from 2D and 3D CCSN simulations covering a progenitor mass range between 11$\mathrm{M_{\odot}}$\, and 40$\mathrm{M_{\odot}}$\, and different equations of state for both a network of up to five second-generation detectors and the proposed third-generation detectors Einstein Telescope and Cosmic Explorer. Our study shows that it will be possible to infer PNS properties for CCSN events occurring in the vicinity of the Milky Way, up to the Large Magellanic Cloud, with the current generation of gravitational-wave detectors

A first comparison of search methods for gravitational wave bursts using LIGO and Virgo simulated data

We present a comparative study of 6 search methods for gravitational wave bursts using simulated LIGO and Virgo noise data. The data's spectra were chosen to follow the design sensitivity of the two 4km LIGO interferometers and the 3km Virgo interferometer. The searches were applied on replicas of the data sets to which 8 different signals were injected. Three figures of merit were employed in this analysis: (a) Receiver Operator Characteristic curves, (b) necessary signal to noise ratios for the searches to achieve 50 percent and 90 percent efficiencies, and (c) variance and bias for the estimation of the arrival time of a gravitational wave burst.Comment: GWDAW9 proceeding

Detection in coincidence of gravitational wave bursts with a network of interferometric detectors (I): Geometric acceptance and timing

Detecting gravitational wave bursts (characterised by short durations and poorly modelled waveforms) requires to have coincidences between several interferometric detectors in order to reject non-stationary noise events. As the wave amplitude seen in a detector depends on its location with respect to the source direction and as the signal to noise ratio of these bursts are expected to be low, coincidences between antennas may not be so likely. This paper investigates this question from a statistical point of view by using a simple model of a network of detectors; it also estimates the timing precision of a detection in an interferometer which is an important issue for the reconstruction of the source location, based on time delays.Comment: low resolution figure 1 due to file size problem

Attenuation Length of light in the CHIPS-M Water Cherenkov Detector

The water at the proposed site of the CHIPS water Cherenkov detector has been studied to measure its attenuation length as a function of filtering time. A 3.2m vertical column was filled with the water from the Wentworth Pit, proposed site of the CHIPS deployment. Results consistent with attenuation lengths of up to 100m have been observed at this wavelength with filtration and UV sterilization alone