1,721,782 research outputs found
Estimation of the gravitational wave polarizations from a nontemplate search
Get PDFGravitational wave astronomy is just beginning, after the recent success of the four direct detections of binary black hole (BBH) mergers and the first observation from a binary neutron star inspiral, with the expectation of many more events to come. Given the possibility to detect waves from not exactly modeled astrophysical processes, it is fundamental to be ready to calculate the polarization waveforms in the case of searches using nontemplate algorithms. In such a case, the waveform polarizations are the only quantities that contain direct information about the generating process. We present the performance of a new valuable tool to estimate the inverse solution of gravitational wave transient signals, starting from the analysis of the signal properties of a nontemplate algorithm that is open to a wider class of gravitational signals not covered by template algorithms. We highlight the contributions to the wave polarization associated with the detector response, the sky localization, and the polarization angle of the source. In this paper we present the performances of such a method and its implications by using two main classes of transient signals, resembling the limiting case for most simple and complicated morphologies. The performances are encouraging for the tested waveforms: the correlation between the original and the reconstructed waveforms spans from better than 80% for simple morphologies to better than 50% for complicated ones. For a nontemplate search these results can be considered satisfactory to reconstruct the astrophysical progenitor
Revised Predictions of Neutrino Fluxes from Pulsar Wind Nebulae
Get PDFSeveral pulsar wind nebulae (PWN) have been detected in the TeV band in the last decade. TeV emission is typically interpreted in a purely leptonic scenario, but this often requires that the magnetic field in the nebula be much lower than the equipartition value, as well as the assumption of an enhanced density of target radiation at IR frequencies. In this work, we consider the possibility that, in addition to the relativistic electrons and positrons, relativistic hadrons are also present in these nebulae. Assuming that some of the emitted TeV photons are of hadronic origin, we compute the associated flux of ∼1-100 TeV neutrinos. We use IceCube non-detection to put constraints on the fraction of TeV photons that might be contributed by hadrons and estimate the number of neutrino events that can be expected from these sources in ANTARES and KM3Net
Core collaApse Supernovae parameTers estimatOR a novel software for data analysis
No full textIn this poster we presented the novel open-access software for core collapse supernovae optical analysis: CASTOR. This software enables the reconstruction of synthetic light curves and spectra via a machine learning technique that allows to retrieve the complete parameter map of a supernova having as only input the multi-band photometry data. This approach is particularly significant in view of the Large Synoptic Survey Telescope (LSST), which will create a deficiency in spectroscopic data necessary to confirm the nature and fully characterize each event
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Deep learning for core-collapse supernova detection
Get PDFThe detection of gravitational waves from core-collapse supernova (CCSN) explosions is a challenging task, yet to be achieved, in which it is key the connection between multiple messengers, including neutrinos and electromagnetic signals. In this work, we present a method for detecting these kind of signals based on machine learning techniques. We tested its robustness by injecting signals in the real noise data taken by the Advanced LIGO-Virgo network during the second observing run, O2. We trained a newly developed Mini-Inception Resnet neural network using time-frequency images corresponding to injections of simulated phenomenological signals, which mimic the waveforms obtained in 3D numerical simulations of CCSNe. With this algorithm we were able to identify signals from both our phenomenological template bank and from actual numerical 3D simulations of CCSNe. We computed the detection efficiency versus the source distance, obtaining that, for signal to noise ratio higher than 15, the detection efficiency is 70% at a false alarm rate lower than 5%. We notice also that, in the case of the O2 run, it would have been possible to detect signals emitted at 1 kpc of distance, while lowering down the efficiency to 60%, the event distance reaches values up to 14 kpc
Estimating the neutrino flux from choked gamma-ray bursts
No full textThe strong constraints from the Fermi-LAT data on the isotropic gamma-ray background suggest that the neutrinos observed by IceCube might possibly come from sources that are hidden to gamma-ray observations. A possibility recently discussed in the literature is that neutrinos may come from jets of collapsing massive stars which fail to break out of the stellar envelope, and for this reason they are known as choked jets, or choked Gamma-Ray Bursts (GRBs). In this paper, we estimate the neutrino flux and spectrum expected from these sources, focusing on Type II SNe. We perform detailed calculations of p? interactions, accounting for all the neutrino production channels and scattering angles. We provide predictions of expected event rates for operating neutrino telescopes, such as ANTARES and IceCube, as well as for the future generation telescope KM3NeT. We find that for GRB energies channeled into protons spanning between ~ 1051-1053 erg, choked GRBs may substantially contribute to the observed astrophysical neutrino flux, if their local rate is ~ 80-1 Gpc-3yr-1 respectively
Detection prospects for multi-GeV neutrinos from collisionally heated GRBs
Get PDFNeutrinos with energies ranging from GeV to sub-TeV are expected to be produced in gamma-ray bursts (GRBs) as a result of the dissipation of the jet kinetic energy through nuclear collisions occurring around or below the photosphere, where the jet is still optically thick to high-energy radiation. So far, the neutrino emission from the "inelastic collisional model"in GRBs has been poorly investigated from the experimental point of view. In the present work, we discuss prospects for identifying neutrinos produced in such collisionally heated GRBs with the large volume neutrino telescopes KM3NeT and IceCube, including their low-energy extensions, KM3NeT/ORCA and DeepCore, respectively. To this aim, we evaluate the detection sensitivity for neutrinos from both individual and stacked GRBs, exploring bulk Lorentz factor values ranging from 100 to 600. As a result of our analysis, individual searches appear feasible only for extreme sources, characterized by gamma-ray fluence values at the level of Fγ≥10-2 erg cm-2. In turn, it is possible to detect a significant flux of neutrinos from a stacking sample of ∼900 long GRBs (that could be detected by current gamma-ray satellites in about five years) already with DeepCore and KM3NeT/ORCA. The detection sensitivity increases with the inclusion of data from the high-energy telescopes, IceCube and KM3NeT/ARCA, respectively
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