Η παρούσα διατριβή παρουσιάζει τα αποτελέσματα μιας συστηματικής έρευνας των πληθυσμών Υπολειμμάτων Υπερκαινοφανών (Υ/Υ) σε έξι κοντινούς γαλαξίες (NGC 2403, NGC 3077, NGC 4214, NGC 4395, NGC 4449 και NGC 5204) βασισμένη σε αρχειακά δεδομένα του δορυφόρου ακτίνων-Χ Chandra, και σε βαθειές οπτικές παρατηρήσεις με τα στενά φίλτρα Hα (λ 6563) και [SΙΙ] (λλ 6716, 6731) καθώς και φασματοσκοπικές παρατηρήσεις. Η ταξινόμηση των Υ/Υ επιλεγμένων στις ακτίνες-Χ βασίστηκε στα μαλακά, θερμικά φάσματα (kT < 3 keV) των πηγών στις ακτίνες-Χ ή στα χρώματά τους στις ακτίνες-Χ. Αντίστοιχα, η ταξινόμηση των οπτικών Υ/Υ βασίστηκε στο καθιερωμένο κριτήριο του λόγου των γραμμών εκπομπής [SΙΙ](λλ 6716, 6731)/Hα > 0.4. Εντοπίστηκαν 37 θερμικά Υ/Υ στις ακτίνες-Χ, 30 εκ των οποίων είναι νέες ανακαλύψεις και ~400 (~350 από αυτά είναι νέες ανιχνεύσεις) φωτομετρικά Υ/Υ, για 67 από τα οποία πιστοποιήθηκε φασματοσκοπικά η φύση τους ως Υ/Υ. Πολλοί από τους γαλαξίες στο δείγμα μας μελετώνται για πρώτη φορά στις ακτίνες-Χ (NGC 4214, NGC 4395 και NGC 5204) ή στο οπτικό μέρος του φάσματος (NGC 4395, NGC 3077) με συστηματικό τρόπο, καταλήγοντας στην ανακάλυψη αρκετών νέων Υ/Υ. Σε πολλές περιπτώσεις, η ταξινόμηση των πηγών ως Υ/Υ στις ακτίνες-Χ ή στο οπτικό μέρος του φάσματος επιβεβαιώνεται από ομόλογα Υ/Υ που έχουν ανιχνευθεί σε άλλα μήκη κύματος, δείχνοντας ότι οι μέθοδοι ανίχνευσης που χρησιμοποιούμε είναι αξιόπιστες. Συζητάμε τις ιδιότητες (π.χ. φωτεινότητα, θερμοκρασία, πυκνότητα, ταχύτητα σοκ) των Υ/Υ σε διάφορους τύπους γαλαξιών και ως εκ τούτου διαφορετικά περιβάλλοντα, προκειμένου να δούμε την εξάρτησή τους από το μεοσαστρικό μέσο. Συσχετίζουμε παραμέτρους των ανιχνευμένων οπτικών Υ/Υ (λόγος [SΙΙ]/Hα, φωτεινότητα) με τις παραμέτρους των αντίστοιχων Υ/Υ στις ακτίνες-Χ (θερμοκρασία, φωτεινότητα, πυκνότητα) προκειμένου να κατανοήσουμε την εξέλιξή τους. Μερικά από τα πιο ενδιαφέροντα αποτελέσματα αυτής της έρευνας είναι τα ακόλουθα: α) Βρίσκουμε ότι τα Υ/Υ που είναι ανιχνευμένα στις ακτίνες-Χ και βρίσκονται σε άμορφους γαλαξίες φαίνεται να είναι πιο λαμπρά από εκείνα στους σπειροειδείς γαλαξίες. Αποδίδουμε αυτό το γεγονός στη χαμηλότερη μεταλλικότητα των άμορφων γαλαξιών από αυτή των σπειροειδών (η χαμηλότερη μεταλλικότητα δημιουργεί πρόγονους αστέρες μεγαλύτερης μάζας) ή στις υψηλότερες τοπικές πυκνότητες που παρατηρούνται στο μεσοαστρικό μέσο των άμορφων γαλαξιών, β) Η σύγκριση του αριθμού των παρατηρούμενων λαμπρών Υ/Υ στις ακτίνες-Χ με τον αριθμό αυτών που αναμένονται με βάση τις κατανομές φωτεινότητας των Υ/Υ στις ακτίνες-Χ στα Νέφη του Μαγγελάνου και στον M33, δείχνουν ότι κατανομές φωτεινότητας των Υ/Υ μεταξύ σπειροειδών και άμορφων γαλαξιών είναι διαφορετικές, από αυτές που αφορούν τα Υ/Υ στους άμορφους γαλαξίες και τείνουν να είναι πιο επίπεδες, γ) Βρίσκουμε ότι υπάρχει διαφορά στους λόγους [NΙΙ]/Hα των Υ/Υ μεταξύ διαφορετικών τύπων γαλαξιών, το οποίο κατά πάσα πιθανότητα οφείλεται σε διαφορές στη μεταλλικότητά τους και δ) Υπάρχουν ισχυρές ενδείξεις για μια γραμμική σχέση μεταξύ του αριθμού των λαμπρών Υ/Υ στο οπτικό και στις ακτίνες-Χ και του ρυθμού αστρογένεσης των γαλαξιών του δείγματος. / This thesis presents the results of a comprehensive investigation of the Supernova Remnant (SNR) populations in six nearby galaxies (NGC 2403, NGC 3077, NGC 4214, NGC 4395, NGC 4449 and NGC 5204) based on Chandra archival data and deep optical narrow-band Hα and [SΙΙ] images, as well as spectroscopic observations. The classification of X-ray emitting SNRs was based on their soft thermal spectra (kT < 3 keV) or their X-ray colors and for optically-emitting SNRs on the well-established emission-line flux criterion of [SΙΙ](λλ 6716, 6731)/Hα(λ 6563) > 0.4. We have identified 37 X-ray selected thermal SNRs, 30 of which are new discoveries and ~400 optical SNRs (~350 are new detections), for 67 of which we spectroscopically verified their shock-excited nature. Many of the galaxies in our sample are studied for the first time in the X-ray (NGC 4214, NGC 4395, and NGC 5204) or optical (NGC 4395, NGC 3077) band in a self-consistent way, resulting in the discovery of many new SNRs. In many cases, the X-ray and optical classifications are confirmed based on the identification of SNR counterparts in other wavelengths, giving us confidence that the detection methods we use are robust. We discuss the properties (e.g. luminosity, temperature, density, shock velocity) of the X-ray/optically detected SNRs in different types of galaxies and hence different environments, in order to address their dependence on their interstellar medium. We compare optical ([SΙΙ]/Hα ratio, luminosity) and X-ray parameters (temperature, luminosity, density) of the detected SNRs, in order to understand their evolution and investigate possible selection effects. The most intriguing results of this survey are the following: a) We find that X-ray selected SNRs in irregular galaxies appear to be more luminous than those in spirals. We attribute this either to the lower metallicities and therefore more massive progenitor stars of irregular galaxies or to the higher local densities of the interstellar medium, b) A comparison of the numbers of observed luminous X-ray selected SNRs with those expected from the luminosity functions of X-ray SNRs in the Magellanic Clouds and M33 suggest different luminosity distributions between the SNRs in spiral and irregular galaxies, with the latter tending to have flatter distributions, c) We find that there is a difference in [NΙΙ]/Hα line ratios of the SNR populations between different types of galaxies which is the result of the low metalicity of irregular galaxies, and d) We find evidence for a linear relation between the number of luminous optical or X-ray SNRs and Star Formation Rate in our sample of galaxies.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / Emission line intensities from ionized nebulae are an important information source about this objects. There are many data on line intensities emitted from supernova remnants scattered in the literature. However, these data can be more efficiently used if avaliable in the form of an electronic data base. Based on this, it was made a catalog of emission line intensities of supernova remnants with data obtained from the literature, including lines in the spectral range of 900Å to 100 mm. About 300 supernova remnants and more than 25 000 emission line intensities were cataloged, including adittional information associated to the objects and the observations. As a demonstration of the aplicability of this catalog, diagnostic diagrams were made with emission line intensities from supernova remnants and from HII regions, using the line ratios [O III] l5007/Hb, [N II] l6583/Ha, [O II] l3727/Hb, [S II] (l6716+l6730)/Ha and [O I] l6300/Ha. Besides these traditional diagrams, the large amount of data in the catalog allowed the construction of others diagrams using relatively weak lines, rarely measured. The diagrams were effective for the classification and discrimination of these classes of objects. It was also verified the values of the ratios [O III] l5007/l4959 and [N II] l6584/l6548, which returned results in agreement with some others published. Moreover, considering the ultraviolet spectroscopy advances in recent decades, it is presented an history of the instrumentation and its performance evolution, regarding some topics that show the importance of the studies about the ultraviolet spectra of supernova remnants. Finally, a list of all ultraviolet emission lines already measured in supernova remnants until 2010 was made, and compared with a similar list created in 1996. It was found that many new lines were detected and some multiplets became resolved since then. Each one of the 142 lines was identified by its wavelength, the ion and parameters of the transition that generates it. This table may be used as a reference for identifying emission lines in supernova remnants in future studies. / As intensidades de linhas de emissão de nebulosas ionizadas constituem uma importante fonte de informação sobre esses objetos. São numerosos os dados que podem ser encontrados em diferentes artigos da literatura referentes a intensidades de linhas emitidas por remanescentes de supernovas. Porém, esses dados podem ser mais eficientemente utilizados se disponibilizados em conjunto e de maneira organizada, ou seja, na forma de um catálogo. Com base nisso, foi construído um catálogo de intensidades de linhas de emissão de remanescentes de supernovas com dados extraídos da literatura, incluindo linhas no intervalo espectral de 900 Å até 100 mm. Cerca de 300 remanescentes de supernovas e mais de 25 000 intensidades de linhas de emissão foram catalogadas, incluindo informações adicionais associadas ao objeto e à observação. Como demonstração de aplicação do catálogo, foram construídos diagramas de diagnóstico com intensidades de linhas de emissão de remanescentes de supernovas e de regiões HII, utilizando as razões de intensidades de linhas [O III] l5007/Hb, [N II] l6583/Ha, [O II] l3727/Hb, [S II] (l6716+l6730)/Ha e [O I] l6300/Ha. Além desses diagramas tradicionais, a grande quantidade de dados do catálogo permitiu construir novos diagramas utilizando linhas relativamente fracas, raramente medidas. Os diagramas mostraram-se eficientes para a classificação e distinção dessas classes de objetos. Também verificou-se os valores das razões [O III] l5007/l4959 e [N II] l6584/l6548, retornando valores em concordância com outros publicados. Por fim, considerando os avanços na espectroscopia ultravioleta das últimas décadas, apresenta-se um histórico da instrumentação utilizada e da evolução de sua performance, considerando também alguns tópicos que mostram a importância dos estudos espectroscópicos na faixa do ultravioleta em remanescentes de supernovas. Construiu-se uma lista com todas as linhas de emissão do ultravioleta já medidas em remanescentes de supernovas até o ano de 2010, fazendo-se um comparativo com as linhas medidas até o ano de 1996. Verificouse que várias novas linhas foram detectadas e que alguns multipletos passaram a ser resolvidos. Essas 142 linhas são identificadas pelo seu comprimento de onda, pelo íon e por parâmetros das transições que as geram, e são listados os remanescentes de supernovas em que cada linha foi medida. Essa tabela pode ser utilizada como referência na identificação das linhas em futuros estudos de remanescentes de supernovas.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-07-25T21:57:03Z No. of bitstreams: 1 IcaroKennedyFrancelinoMoura_DISSERT.pdf: 6308092 bytes, checksum: 65c9e0d99b3ea645902b37237e873ed1 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-08-03T20:32:51Z (GMT) No. of bitstreams: 1 IcaroKennedyFrancelinoMoura_DISSERT.pdf: 6308092 bytes, checksum: 65c9e0d99b3ea645902b37237e873ed1 (MD5) / Made available in DSpace on 2016-08-03T20:32:51Z (GMT). No. of bitstreams: 1 IcaroKennedyFrancelinoMoura_DISSERT.pdf: 6308092 bytes, checksum: 65c9e0d99b3ea645902b37237e873ed1 (MD5) Previous issue date: 2016-03-02 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior (CAPES) / Grandes esfor?os observacionais t?m sido direcionados para investigar a natureza da chamada energia escura. Nesta disserta??o derivamos v?nculos sobre modelos de energia escura utilizando tr?s diferentes observ?veis: medidas da taxa de expans?o H(z) (compiladas por Meng et al. em 2015); m?dulo de dist?ncia de 580 Supernovas do Tipo Ia (cat?logo Union Compilation 2.1, 2011); e as observa??es do pico de oscila??o de b?rions (BAO) e a radia??o c?smica de fundo (CMB) utilizando a chamada raz?o CMB/BAO, que relaciona 6 picos de BAO (um pico determinado atrav?s dos dados do Survey 6dFGS, dois atrav?s do SDSS e tr?s atrav?s do WiggleZ). A an?lise estat?stica utilizada foi o m?todo do ?2 m?nimo (marginalizado ou minimizado sobre h sempre que poss?vel) para vincular os par?metro cosmol?gicos: ?m, ??, ? e ??0. Esses testes foram aplicados em duas parametriza??es do par?metro ? da equa??o de estado da energia escura, p=?? (aqui, p ? a press?o e ? ? a densidade de energia da componente). Numa, ? ? considerado constante e menor que -1/3, conhecido como modelo XCDM; na outra parametriza??o, o par?metro da equa??o de estado varia com o redshift, no qual o chamamos de Modelo GS. Esta ?ltima parametriza??o ? baseada em argumentos que surgem da teoria da infla??o cosmol?gica. Para efeitos de compara??o tamb?m foi feita a an?lise do modelo ?CDM. A compara??o dos modelos cosmol?gicos com as diferentes observa??es leva a diferentes melhores ajustes. Assim, para classificar a viabilidade observacional dos diferentes modelos te?ricos, utilizamos dois crit?rios de informa??o, ou seja, o crit?rio de informa??o bayesiana (BIC) e o crit?rio de informa??o Akaike (AIC). A ferramenta matriz de Fisher foi incorporada aos nossos testes para nos fornecer a incerteza dos par?metros de cada modelo te?rico. Verificamos que a complementariedade dos testes ? necess?ria para n?o termos espa?os param?tricos degenerados. Fazendo o processo de minimiza??o encontramos, dentro da regi?o de 1? (68%), que para o Modelo XCDM os melhores ajustes dos par?metros s?o ?m=0,28?0,012 e ?X=-1,01?0,052. Enquanto que para o Modelo GS os melhores ajustes s?o ?m=0,28?0,011 e ??0=0,00?0,059. E realizando uma marginaliza??o encontramos, dentro da regi?o de 1? (68%), que para o Modelo XCDM os melhores ajustes dos par?metros s?o ?m=0,28?0,012 e ?X=-1,01?0,052. Enquanto que para o Modelo GS os melhores ajustes s?o ?m=0,28?0,011 e ??0=0,00?0,059. / A significant observational effort has been directed to investigate the nature of the so-called dark energy. In this dissertation we derive constraints on dark energy models using three different observable: measurements of the Hubble rate H(z) (compiled by Meng et al. in 2015.); distance modulus of 580 Supernovae Type Ia (Union catalog Compilation 2.1, 2011); and the observations of baryon acoustic oscilations (BAO) and the cosmic microwave background (CMB) by using the so-called CMB/BAO of six peaks of BAO (a peak determined through the Survey 6dFGS data, two through the SDSS and three through WiggleZ). The statistical analysis used was the method of the ?2 minimum (marginalized or minimized over h whenever possible) to link the cosmological parameter: m, ? and ??0. These tests were applied in two parameterization of the parameter ? of the equation of state of dark energy, p = ?? (here, p is the pressure and ? is the component of energy density). In one, ? is considered constant and less than -1/3, known as XCDM model; in the other the parameter of state equantion varies with the redshift, where we the call model GS. This last model is based on arguments that arise from the theory of cosmological inflation. For comparison it was also made the analysis of model CDM. Comparison of cosmological models with different observations lead to different optimal settings. Thus, to classify the observational viability of different theoretical models we use two criteria information, the Bayesian information criterion (BIC) and the Akaike information criteria (AIC). The Fisher matrix tool was incorporated into our testing to provide us with the uncertainty of the parameters of each theoretical model. We found that the complementarity of tests is necessary inorder we do not have degenerate parametric spaces. Making the minimization process we found (68%), for the Model XCDM the best fit parameters are m = 0.28 ? 0, 012 and ?X = ?1.01 ? 0, 052. While for Model GS the best settings are m = 0.28 ? 0, 011 and ??0 = 0.00 ? 0, 059. Performing a marginalization we found (68%), for the Model XCDM the best fit parameters are m = 0.28 ? 0, 012 and ?X = ?1.01 ? 0, 052. While for Model GS the best settings are M = 0.28 ? 0, 011 and ??0 = 0.00 ? 0, 059.

Le cadre global des oscillations de neutrinos est maintenant bien compris et nous quittons une ère d'exploration pour une ère de précision. L'expérience Double Chooz a pour but de mesurer l'angle de mélange theta13 par l'étude des oscillations des antineutrinos électroniques produits par les réacteurs de la centrale nucléaire de Chooz. Dans cette thèse, une sélection préliminaire des neutrinos détectés dans le détecteur proche est présentée. Les résultats les plus récents de Double Chooz, desquels sont extraits la mesure de theta13 la plus précise que l'expérience peut fournir à ce jour, seront également discutés. La géométrie de l'expérience, relativement simple, représente un avantage considérable afin d'effecteur des études de directionalité des neutrinos dont les résultats, obtenus en analysant les jeux de données les plus récents avec captures sur Gd et H, sont présentés. Ce concept de directionalité peut être appliqué à l'astronomie/astrophysique en offrant la possibilité de localiser des supernovas après détection de leurs neutrinos. Les résultats de simulations de directionalité effectuées avec différentes combinaisons de détecteurs seront présentées. Enfin, plusieurs anomalies pourraient s'expliquer par l'existence de nouveaux états, stériles, de neutrinos. Le but de l¿expérience CeSOX est de confirmer ou réfuter cette hypothèse en déployant une source radioactive à coté d'un grand détecteur comme KamLAND ou Borexino. Dans cette thèse seront présentés les résultats des simulations de signaux et de bruits de fond effectuées afin de valider le principe de l'expérience et de s'assurer de sa sensibilité à l'observation d'une oscillation vers un neutrino stérile. / The framework of neutrino oscillations is quite well-understood and now requires precision rather than exploration. The Double Chooz experiment aims at measuring the theta13 mixing angle through the oscillations of electronic antineutrinos produced by the reactors of the Chooz nuclear power plant. The comparison of the interaction rates and spectral shapes in the two Double Chooz's detectors allows the observation of a disappearance and a spectral distortion, both driven by theta13. In this thesis, a preliminary neutrino selection with the near detector, whose data taking started in December 2014, has been performed. The most recent results of Double Chooz, providing the most precise measurement of the experiment, are presented as well.The simple layout of Double Chooz is a strong advantage to conduct directionality studies. Results of these studies using the most recent neutrino candidates with neutron captures on Gd and H are showed. Neutrino directionality can be applied to astronomy, with the localization of core-collapse supernovae. To this purpose, results of directionality measurements performed with combinations of large neutrino detectors over the globe are presented.Finally, recent anomalies observed in short baseline experiments provided hints of the hypothetical existence of additional sterile neutrino states. The goal of the CeLAND/CeSOX experiment is to test this hypothesis by deploying a radioactive source next to a large liquid scintillator detector such as KamLAND or Borexino. In this thesis, are presented results of signal and background simulations performed to validate the design and assess the sensitivity of such an experiment.

This thesis contributes to the field of dark energy and observational cosmology. We have investigated possible direction dependent systematic signal and non-Gaussian features in the supernovae (SNe) Type Ia data. To detect these effects we propose a new method of analysis. Although We have used this technique on SNe Ia data, it is quite general and can be applied to other data sets as well. SNe Ia are the most precise known distance indicators at the cosmological distances. Their constant peak luminosity(after correction) makesthem standard candles and hence one can measure the distances in the universe using SNe Ia. This distance measurement can determine various cosmological parameters such as the Hubble constant, various components of matter density and dark energy from, the SNe Ia observations. Recent SNe Ia observations have shown that the expansion of the universe is currently accelerating. This recent acceleration is explained by invoking a component in the universe having negative pressure and is termed as dark energy. It can be described by a homogeneous and isotropic fluid with the equation of state P = wρ, where w is allowed to be negative. A constant(Λ) in the Einstein equation(known as cosmological constant) can explain the acceleration, in the fluid model it can be modeled with w = -1. Other models of dark energy with w = -1 can also explain the acceleration, however the precise nature of this mysterious component remains unknown. Although there exist a wide range of dark energy models, cosmological constant provides the simplest explanation to the acceleration of the expansion of the Universe. The equation of state parameter w has been investigated by recent surveys but the results are still consistent with a wide range of dark energy models. In order to discriminate among various cosmological models we need an even more precise measurement of distance and error bars in the SNe Ia data. From the central limit theorem we expect Gaussian errors in any experiment that is free from systematic noise. However in astronomy we do not have a control over the observed phenomena and thus can not control the systematic errors (due to some physical processes in the Universe) in the observed data. The only possible way to deal with such data is by using appropriate statistical techniques. Among these systematic features the direction dependent features are more dangerous ones since they may indicate a preferred direction in the Universe. To address the issue of direction dependent features we have developed a new technique(Δ statistic henceforth) which is based on the extreme value theory. We have applied this technique to the available high-z SNe Ia data from Riess et al.(2004)and Riess et al.(2007). In addition we have applied it to the HST data from HST key project for H0 measurement. Below we summarize the material presented in the thesis. Chapter wise summary of the thesis In the first chapter we present an introductory discussion of the various basic cosmological notions eg. Cosmological Principle (CP), observational evidence in support of CP and departures from it, distance measures and large scale structure. The observed departures from the CP could be present due to the systematic errors and/or non-Gaussian error bars in the data. We discuss the errors involved in the measurement process Basics of statistical techniques : In the next two chapters we discuss basics of the statistical techniques used in this thesis and extreme value theory. Extreme value theory describes how to calculate the distribution of extreme events. The simplest of the distributions of the extremes is known as the Gumbel distribution. We discuss features of the Gumbel distribution since it is used extensively in our analysis. Δ statistic and features in the SNe data : In the fourth chapter we derive Δ statistic and apply it to the SNe Ia data sets. An outline of the Δ statistic is as follows : a) We define a plane which cuts the sky into hemispheres. This plane will divide the data into two subsets, one in each hemisphere. b) Now we calculate the χ2 in each hemisphere for an FRW universe assuming a flat geometry. c) The difference of χ2 in the two hemisphere is calculated and maximized by rotating the plane. This maximum should follow the Gumbel distribution. Since it is difficult to calculate the analytic form of Gumbel distribution we calculate it numerically assuming Gaussian error bars. This gives the theoretical distribution for the above calculated maximum of difference of χ2 . The results indicate that GD04 shows systematic effects as well non-Gaussian features while the set GD07 is better in terms of systematic effects and non-Gaussian features. Non-Gaussian features in the H0 data : HST key project measures the value of Hubble constant at the level of 10% accuracy, which requires precise measurement of the distances. It uses various methods to measure distance for instance SNe Ia, Tully-Fisher relation, surface-brightness fluctuations etc. In the fifth chapter we apply Δ statistic to the HST Key Project data in order to check the presence of non-Gaussian and direction dependent features. Our results show that although this data set seems to be free of direction dependent features, it is inconsistent with the Gaussian errors. Analytic Marginalization : The quantities of real interest in cosmology are ΩM and ΩΛ, Hubble constant could in principle be treated as a nuisance parameter. It would be useful to marginalize over the nuisance parameter. Although it can be done numerically using Bayesian method, Δ statistic does not allow it. In chapter six we propose a method to marginalize over H0 analytically. The χ2 in this case is a complicated function of errors in the data. We compare this analytic method with the Bayesian marginalization method and results show that the two methods are quite consistent. We apply the Δ statistic to the SNe data after the analytic marginalization. Results do not change much indicating the insensitivity of the direction de-pendent features to the Hubble constant. A variation to the Δ statistic: As has been discussed earlier that, it is difficult to calculate the theoretical distribution of Δ in general. However if the parent distribution follows certain conditions it is possible to derive the analytic form for the Gumbel distribution for Δ. In the seventh chapter we derive a variation to the Δ statistic in a way that allows us to calculate the analytic distribution. The results in this case are different from those presented earlier, but they confirm the same direction dependence and non-Gaussian features in the data.

Les explosions gamma (GRB) sont des évènements extrêmement violents. Ils sont sommairement classifiés en deux groupes par leur durée : les courts et les longs. Cette classification a permis de déterminer l'origine des GRBs : une collision entre deux objets compacts pour les courts ou l'explosion d'une étoile très massive pour les longs. Une meilleure classification des GRBs longs pourrait mieux contraindre leurs propriétés. Dans ma thèse, je présente des évidences de l'existence d'une sous-classification des GRBs basés sur la faible luminosité de leurs derniers reflets. Ces explosions sont appelées Low-Luminosity Afterflow (LLA). Je présente la technique de réduction des données, la méthode de sélection de ces GRBs ainsi que leurs principales propriétés. Leur lien avec les supernovæ (SN) est mis en évidence car 64 % de tous les GRBs associés à des Sns sont des LLA GRBs. Finalement, je présente d'autres propriétés comme leur fréquence, qui semble indiquer une nouvelle distincte classe, les propriétés de leurs galaxies hôte qui montrent que ces explosions ont pour origines des galaxies formant beaucoup d'étoiles. De plus, je montre qu'il est difficile de réconcilier les différences entre les GRBs normaux et les LLA GRBs en ne considérant que des effets instrumentaux et environnementaux, ou bien une géométrie différente. Donc je conclue que les deux classes de GRBs ont des propriétés différentes. En basant l'argumentation sur la fonction de masse initiale, sur la fréquence des LLA GRBs et sur le type de SNs qui les accompagnent, j'indique qu'un système binaire est favorisé pour leur origine. / Gamma-ray bursts (GRB) are extreme events. They are crudely classified into two groups based on their duration, namely the short and long bursts. Such a classification has proven to be useful to determine their progenitors: the merger of two compact objects for short bursts and the explosion of a massive star for long bursts. Further classifying the long GRBs might give tighter constraints on their progenitor and on the emission mechanism(s). In my thesis, I present evidence for the existence of a sub-class of long GRBs, based on their faint afterglow emission. These bursts were named low-luminosity afterglow (LLA) GRBs. I discuss the data analysis and the selection method, and their main properties are described. Their link to supernova is strong as 64\% of all the bursts firmly associated to SNe is LLA GRBs. Finally, I present additional properties of LLA GRBs: the study of their rate density, which seems to indicate a new distinct third class of events, the properties of their host galaxies, which show that they take place in young star-forming galaxies. Additionally, I show that it is difficult to reconcile all differences between normal long GRBs and LLA GRBs only by considering instrumental or environmental effects, different ejecta content or a different geometry for the burst. Thus, I conclude that LLA GRBs and normal long GRBs should have different properties. In a very rudimentary discussion, I indicate that a binary system is favored in the case of LLA GRB. The argument is based on the initial mass function of massive stars, on the larger rate density of LLA GRBs compared to the rate of normal long GRBs and on the type of accompanying SNe.

No description available.

Nous présentons une nouvelle approche pour déterminer, d'une façon plus précise, l'indice spectral et sa variation spatiale dans les restes de supernova (RSN). Sachant que les RSNs sont des sources de rayonnement non-thermique (rayonnement synchrotron), nous éliminons la contribution du rayonnement thermique à l'aide de la corrélation entre le continu radio à 1420 MHz (CGPS) et le continu infrarouge à 60 pm (IRAS). De plus, nous étudions la contribution de l'émission de la poussière associée au gaz neutre HI. Cette contribution permet, à l'aide d'une simple soustraction, d'isoler l'émission associée au gaz ionisé (HII) seulement. La méthode a été appliquée à l'étude de l'indice spectral de cinq RSNs, soit G78.2+2.1, VRO 42.05.01, CTA1, Boucle du Cygne et HB 3. Dans certains cas, les indices spectraux obtenus sont significativement plus élevés que les valeurs obtenues précédemment.

This study focusses on modelling important aspects of the evolution of pulsar wind nebulae using two different approaches. The first uses a hydrodynamic model to simulate the morphological evolution of a spherically-symmetric composite supernova remnant that is expanding into a homogeneous interstellar medium. In order to extend this model, a magnetic field is included in a kinematic fashion, implying that the reaction of the fluid on the magnetic field is taken into account, while neglecting any counter-reaction of the field on the fluid. This approach is valid provided that the ratio of electromagnetic to particle energy in the nebula is small, or equivalently, for a large plasma β environment. This model therefore allows one to not only calculate the evolution of the convection velocity but also, for example, the evolution of the average magnetic field. The second part of this study focusses on calculating the evolution of the energy spectra of the particles in the nebula using a number of particle evolution models. The first of these is a spatially independent temporal evolution model, similar to the models that can be found in the literature. While spatially independent models are useful, a large part of this study is devoted to developing spatially dependent models based on the Fokker-Planck transport equation. Two such models are developed, the first being a spherically-symmetric model that includes the processes of convection, diffusion, adiabatic losses, as well as the non-thermal energy loss processes of synchrotron radiation and inverse Compton scattering. As the magnetic field geometry can lead to the additional transport process of drift, the previous model is extended to an axisymmetric geometry, thereby allowing one to also include this process. / PhD (Space Physics), North-West University, Potchefstroom Campus, 2014

Diese Arbeit berichtet über die Suche nach gepulster und ungepulster hochenergetischer (VHE) Gammastrahlung mit dem High Energy Stereoscopic System (H.E.S.S.) im Energiebereich von 100 GeV bis 100 TeV von drei Pulsaren. Gepulste VHE Gammastrahlung wurde bisher nur fuer den jungen Krebspulsar gefunden. Eine besondere Gruppe von Pulsarwindnebeln (PWN) sind die zusammengesetzten Supernovaüberreste (SNR), bei denen sich ein PWN im Zentrum einer expandierenden SNR Schale befindet. Die Resultate der Suche nach gepulster und ungepulster VHE Gammastrahlung von zwei Millisekundenpulsaren, PSR J0437-4715 und PSR J1824-2452, werden im ersten Teil dieser Arbeit vorgestellt. Teile der Beobachtungen wurden in einer speziellen Triggerkonfiguration (dem Topologischen Trigger mit konvergenter Ausrichtung) durchgeführt, um die Energieschwelle des Instruments zu senken. Kein Hinweis auf gepulste oder ungepulste Emission wurde gefunden und obere Grenzen auf den gepulsten und ungepulsten Fluss wurden bestimmt. Die oberen Grenzen auf den gepulsten Fluss werden mit bestehenden Modellvorhersagen verglichen und erlauben für PSR J1824-2452 den Bereich möglicher Geometrien in einigen Modellen einzuschränken. Die Resultate der Suche nach gepulster und ungepulster VHE Gammastrahlung aus der Richtung des zusammengesetzten SNR Kes 75 werden im zweiten Teil dieser Arbeit präsentiert. Der PWN im Zentrum von Kes 75 wird von einem sehr jungen und energiereichen Pulsar, PSR J1846-0258, angetrieben, der ein aussergewöhnlich starkes Magnetfeld besitzt. Während kein Hinweis auf gepulste Strahlung gefunden wurde, konnte ungepulste Emission von VHE Gammastrahlung von einer Punktquelle mit einer statistischen Signifikanz von 10 sigma nachgewiesen werden. Die VHE Gammastrahlung ist räumlich koinzident mit dem PWN und mit der SNR Schale. Beide werden als mögliche Quelle für die beobachtete Emission diskutiert. Der Pulsar von Kes 75 wäre der jüngste bisher bekannte Pulsar, der einen Pulsarwindnebel antreibt. / This work reports on the search for pulsed and steady very-high energy (VHE) gamma-ray emission in the energy range extending from 100 GeV up to 100 TeV from the direction of three pulsars with the High Energy Stereoscopic System (H.E.S.S.). Pulsed gamma-ray radiation from pulsars with energies beyond 100 GeV was found thus far only for the young and energetic Crab pulsar. A special class of pulsar wind nebulae (PWNe) is associated with composite supernova remnants (SNRs) where the PWN is centered in an expanding SNR shell. In the first part of this thesis, the results on the search for pulsed and steady VHE gamma-ray emission from the two millisecond pulsars, PSR J0437-4715 and PSR J1824-2452, are presented. Parts of the observations were conducted in a special trigger setup (the topological trigger with convergent pointing) to reduce the energy threshold of the instrument. No signal of pulsed or steady emission is found and upper limits on the pulsed and steady gamma-ray flux are derived. The upper limits on the pulsed gamma-ray flux are compared to existing model predictions and, in the case of PSR J1824-2452, allow the range of possible viewing geometries in some models to be constrained. In the second part of this work, results on the search for pulsed and steady VHE gamma-ray emission from the direction of the composite SNR Kes 75 are presented. The PWN in the center of Kes 75 is powered by a very young and powerful pulsar, PSR J1846-0258, that has an exceptionally high magnetic field. While no hint for pulsed emission is found, steady VHE gamma-ray emission is detected with a statistical significance of 10 sigma from a point-like source. The VHE gamma-ray emission is spatially coincident with the PWN and the SNR shell. Both are discussed as a possible origin for the observed emission. The pulsar of Kes 75 would be the youngest pulsar known to date to power a VHE PWN.