1,721,039 research outputs found
Multi-wavelength afterglow numerical code and data analysis of MAGIC very high energy emission from gamma-ray bursts
Full text linkThis PhD thesis is focused on the study of very high energy (E > 100 GeV, VHE) emission from a class of extragalactic transient sources called Gamma-Ray Bursts (GRBs). In particular, I have i) performed data analysis of GRB observations by the MAGIC telescopes; ii) developed a numerical code to exploit such observations and investigate the properties of such astrophysical sources. Despite been discovered more than 50 years ago, GRBs are still a hot topic in Astrophysics. They are extremely energetic phenomena characterized by two emission phases. The first one, called prompt phase, is a rapid and irregular emission in the X and gamma energy range which lasts from milliseconds to thousands of seconds. The second one, called afterglow emission, consists in a long-lasting (days to months) emission covering the entire electromagnetic spectrum, from radio up to gamma-rays and interpreted as the synchrotron radiation produced in the external forward shock scenario. The possible extension of the GRB emission in the high energy (0.5 MeV < E < 100 GeV, HE) and to the very high energy domain has always been one of the most debated open questions in GRB physics. The HE observations have revealed an emission component delayed and lasting longer with respect to the prompt one. Moreover, the highest energy photons observed by Fermi-LAT gave the first evidence that a different radiation mechanism with respect to the synchrotron radiation may be needed to explain such energetic emission and point towards the possibility that a VHE component in GRBs is present. A firm conclusion could not be reached until 2019, when an unprecedented discovery was performed: the ground-based imaging Cherenkov telescopes MAGIC and H.E.S.S. revealed for the first time ever the presence of a VHE emission component in GRB afterglows up to TeV energies. Such detections gave birth to unique studies concerning the radiation processes involved in GRBs. For one of these events, namely GRB190114C, the VHE emission was interpreted as produced via the Synchrotron Self Compton (SSC) mechanism. First, in this thesis I will present MUSE-GRB, a numerical code which I developed to simulate the multi-wavelength GRB afterglow spectra and light curves in the external forward shock scenario. In this code the dynamical evolution of a blastwave interacting with an external medium is reproduced and the time-evolving kinetic equations for electrons, protons and photons are solved. As a result, the afterglow spectra and the light curves at different times and frequencies can be calculated. This flexible and very complete code can be applied to GRB observational data to model the multi-wavelength afterglow emission, thus inferring constraints on several properties of the GRB physics. The code has been intensively tested with analytical prescriptions and with a similar numerical code available in literature. Such tool is able to model the observational data coming from the MAGIC and the H.E.S.S. telescopes and verify their consistency with a SSC origin. In the second part of this thesis I will present the MAGIC data analysis of two GRBs detected in the VHE band, namely GRB190114C and GRB190829A. I performed the dedicated MAGIC data analysis of GRB190114C in the context of a multi-wavelength study of the emission. The MAGIC data were analyzed in several time intervals to investigate a possible spectral evolution in the VHE band. The statistical error and several sources of systematic error were assessed in order to evaluate the firmness and the stability of the data analysis. GRB190829A, successfully detected in the VHE band by the H.E.S.S. telescopes, was also observed by the MAGIC telescopes. Preliminary MAGIC data analysis shows a possible hint of detection. In the context of the study and interpretation of the VHE emission coming from GRBs some applications of MUSE-GRB to GRB190114C and GRB190829A are also presented
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
Constraining the environment of neutrino-emitting regions in jets of FSRQs
Full text linkRecently, the gamma-ray blazar TXS 0506+056 has been proposed as the source of neutrino events detected by IceCube in 2014-15 and 2017. This has further pushed the idea of blazar jets being among those cosmic sites where significant neutrino production may take place. We use a procedure based on source-internal electromagnetic cascading to constrain the environments of neutrino-producing sites in photomeson production models of jetted AGN. The role of external photon fields as the dominant target for particle-photon interactions including possible effects of the anisotropic nature of the interactions in the co-moving jet frame is discussed. We apply this procedure to the 2014-15 neutrino spectrum observed by IceCube from TXS 0506+056 to conduct a comprehensive study of these cascade spectra. By comparing these to the simultaneous multi-wavelength emission of this blazar constraints on the environment of the neutrino-emitting region are derived
Educational outreach activities on cosmic rays: investigate the correlation between muon counts and atmospheric parameters
Full text linkCosmic rays are energetic, subatomic particles constantly reaching the Earth atmosphere from all
directions. Several technological tools currently available can be used to introduce the students
to research activities in the particle physics field. The Legnaro National Laboratories (LNL) of
the Italian Istituto Nazionale di Fisica Nucleare (INFN) host a muon telescope. This telescope
is formed by plastic scintillators and silicon photomultipliers, mostly used for outreach purposes
during the International Cosmic Day (ICD). It is well known that local atmospheric parameters
affect the rate of muons reaching the Earth’s surface. In this contribution, we, along with high
school and bachelor students in Physics at the University of Padova, investigate the anticorrelation
between muon counts and atmospheric pressure. This correlation was measured with the muon
telescope in LNL using the data collected in 2022 and 2023. The results from our analysis confirm
the presence of a significant anticorrelation. Further analyses with a larger datasample allow us
to improve the precision of the result, as well as possibly investigate other atmospheric-related
correlations, such as with temperature and humidity and the variation in time of these correlations.
In addition, we bought a new educational tool: a Cosmic Hunter detector developed by the CAEN
group. We are currently testing the instrument performances and we plan to use this instrument
to confirm our results and explore new possible educational activities for students
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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