1,720,998 research outputs found
Methodological studies on the search for Gravitational Waves and Neutrinos from Type II Supernovae
No full textMethodology of the joint search for Gravitational Wave and Low Energy Neutrino signals from Core-Collapse Supernovae
No full textMultimessenger search for astrophysical bursts with Gravitational Waves and Low Energy Neutrinos
No full textThe next galactic Core Collapse Supernova (CCSN) may represent one of the
most important events in modern astrophysics. The electromagnetic (EM)
emission of the explosion is well understood, but we have no information
about the inner mechanisms that cause it. Neutrinos (\nu) and gravitational
waves (GWs) are the only messengers able to carry information about the inner
working mechanisms of a CCSN. Neutrinos from supernova carry thermodynamic
informations about the collapse, and GWs may reveal the dynamics
involved in the collapse. Via coincident detection and joint analysis
of \nu and GWs from the next nearby core collapse event, we will increase
the knowledge of the astrophysics, neutrino physics, and nuclear physics involved
in these sources.
In this thesis work, we studied the detection efficiency and the misidentification
of networks of \nu detectors to the same burst event, simulating the
detectors background and injecting signals produced using for the emission
a general description of an astrophysical burst of low-energy neutrinos with
a characteristic temporal structure and quasi-thermal spectral shape. We provide
a challenging method to better discriminate under threshold signals
from experimental background. With respect to previous search strategies
this method, without decreasing the detection efficiency, allows to knockingdown
the misidentification probability by a factor of 7, in the worse case,
within a distance of D \sim 20 kpc and, in the better case, this improvement
can reach a factor \sim 20 till an horizon of \si 75 kpc. After the definition of
the methodology to be used to construct the \nu network, we searched for coincident
events between GW data (archival data from LIGO and Virgo taken
before the upgrade to advanced detectors) and the correponding archival
data. We analyzed the obtained results, giving confidence intervals for the
observe coincident event
Multimessenger analysis strategy for core-collapse supernova search: gravitational waves and low-energy neutrinos
Full text linkCore-collapse supernovae are fascinating astrophysical objects for multimessenger studies. Gravitational waves (GWs) are expected to play a role in the supernova explosion mechanism, but their modelling is also challenging due to the stochastic nature of the dynamics and the vast possible progenitors, and moreover, the GW detection from these objects is still elusive with the already advanced detectors. Low-energy neutrinos will be emitted enormously during the core-collapse explosion and can help for the gravitational wave counterpart search. In this work we develop a multi-messenger strategy to search for such astrophysical objects by exploiting a global network of both low-energy neutrino and gravitational wave detectors. First, we discuss how to improve the detection potential of the neutrino sub-network by exploiting the temporal behaviour of a neutrino burst from a core-collapse supernova. We show that with the proposed approach neutrino detectors can gain at least 10% of detection efficiency at the distance where their efficiency drops. Then, we combine the information provided by GW and neutrino in a multimessenger strategy. In particular, we obtain an increase of the probability to detect the GW signal from a CCSN at 6060 kpc from zero when using only GW analysis to 33% with our combined GW-
uν approach. Keywords: multimessenger, supernova, core-collapse, low-energy neutrino, gravitational wave
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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