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Richardson, K. M. "Gamma rays, cosmic rays and local molecular clouds." Thesis, Durham University, 1988. http://etheses.dur.ac.uk/942/.
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Gabici, Stefano. "Gamma ray astronomy and the origin of galactic cosmic rays." Habilitation à diriger des recherches, Université Paris-Diderot - Paris VII, 2011. http://tel.archives-ouvertes.fr/tel-00719791.
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Diffusive shock acceleration operating at expanding supernova remnant shells is by far the most popular model for the origin of galactic cosmic rays. Despite the general consensus received by the model, an unambiguous and conclusive proof of the supernova remnant hypothesis is still missing. In this context, the recent developments in gamma ray astronomy provide us with precious insights into the problem of the origin of galactic cosmic rays, since production of gamma rays is expected both during the acceleration of cosmic rays at supernova remnant shocks and during their subsequent propagation in the interstellar medium. In particular, the recent detection of a number of supernova remnants at TeV energies nicely fits with the model, but it still does not constitute a conclusive proof of it, mainly due to the difficulty of disentangling the hadronic and leptonic contributions to the observed gamma ray emission. The main goal of my research is to search for an unambiguous and conclusive observational test for proving (or disproving) the idea that supernova remnants are the sources of galactic cosmic rays with energies up to (at least) the cosmic ray knee. Our present comprehension of the mechanisms of particle acceleration at shocks and of the propagation of cosmic rays in turbulent magnetic fields encourages beliefs that such a conclusive test might come from future observations of supernova remnants and of the Galaxy in the almost unexplored domain of multi-TeV gamma rays.
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Pinzke, Anders. "Gamma-Ray Emission from Galaxy Clusters : DARK MATTER AND COSMIC-RAYS." Doctoral thesis, Stockholms universitet, Fysikum, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-42453.
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The quest for the first detection of a galaxy cluster in the high energy gamma-ray regime is ongoing, and even though clusters are observed in several other wave-bands, there is still no firm detection in gamma-rays. To complement the observational efforts we estimate the gamma-ray contributions from both annihilating dark matter and cosmic-ray (CR) proton as well as CR electron induced emission. Using high-resolution simulations of galaxy clusters, we find a universal concave shaped CR proton spectrum independent of the simulated galaxy cluster. Specifically, the gamma-ray spectra from decaying neutral pions, which are produced by CR protons, dominate the cluster emission. Furthermore, based on our derived flux and luminosity functions, we identify the galaxy clusters with the brightest galaxy clusters in gamma-rays. While this emission is challenging to detect using the Fermi satellite, major observations with Cherenkov telescopes in the near future may put important constraints on the CR physics in clusters. To extend these predictions, we use a dark matter model that fits the recent electron and positron data from Fermi, PAMELA, and H.E.S.S. with remarkable precision, and make predictions about the expected gamma-ray flux from nearby clusters. In order to remain consistent with the EGRET upper limit on the gamma-ray emission from Virgo, we constrain the minimum mass of substructures for cold dark matter halos. In addition, we find comparable levels of gamma-ray emission from CR interactions and dark matter annihilations without Sommerfeld enhancement.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Accepted.
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Rengifo, Gonzáles Javier. "Disentangling atmospheric cascades started by gamma rays from cosmic rays with CORSIKA." Master's thesis, Pontificia Universidad Católica del Perú, 2017. http://tesis.pucp.edu.pe/repositorio/handle/123456789/8716.
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En este trabajo buscamos un método para diferenciar entre lluvias de partículas producidas por rayos cósmicos y por rayos gamma a energías de TeV, utilizando simulaciones CORSIKA. Este método intenta resolver el problema que existe en la búsqueda de señales de rayos gamma medidos por diversos experimentos frente a un fondo de flujo dominante de hadrones. Los resultados de este trabajo pueden aplicarse al estudio de Explosiones de Rayos Gamma (GRBs). Los GRBs emiten fotones muy energéticos, que al interactuar con la atmósfera terrestre, producen una gran cascada electromagnética de partículas secundarias, las cuales son detectables.
El procedimiento sería simular eventos producidos por fotones, la señal, y protones, el fondo, que son las partículas más abundantes de los rayos cósmicos. Extraemos varios parámetros de los perfiles longitudinales de las lluvias de partículas, caracterizando las lluvias simuladas. Algunos de los parámetros de ajuste más importantes son el m_aximo de lluvia (Xmax), el ancho de la lluvia FWHM, el parámetro de asimetría, el número máximo de partículas Nmax y el comienzo de lluvia XStart. Existen diferentes experimentos utilizando tanques Cherenkov de agua y detectores de fluorescencia que pueden medir estos parámetros de las lluvias.
Hemos probado dos métodos. El primero se basa en cortes simples, mientras que el segundo se basa en un análisis multivariado utilizando el paquete TMVA, que mejora los cortes individuales. El primer método se aplicó a las energías simuladas separadas de 102, 103, 104 y 105 GeV para encontrar cortes adecuados.
Encontramos que Xmax, FWHM, Xstart y Nmax dependen de la energía.
Posteriormente aplicamos estos cortes dependientes de la energía y otros cortes
fijos a una muestra realista, que consiste en 104 eventos de señales (fotones) y 106 eventos de fondo (protones) que cubren un rango de energía de 102 a 105 GeV con diferentes espectros. Además, se introdujo un error en la energía simulada para simular la eficiencia de reconstrucción de energía de un detector. El resultado obtenido deja 54% eventos de señal y 12% eventos de fondo. Aplicando el análisis multivariado TMVA, encontramos que el método Boosted Decision Trees (BDT) era el mejor para distinguir la señal del fondo. El resultado para una eficiencia de señal similar fue 0:7% de eventos de fondo.
Por último, utilizando cortes más estrictos en la BDT para mejorar la significancia, el resultado fue 1 evento de fotón por cada 1000 eventos de protón. Dada la proporción de flujo inicial, significa una capacidad de rechazo de fondo de 103.
Por lo tanto, la viabilidad de la separación gamma/hadrón requiere una mejora adicional.In this work we search for a method to differentiate between particle showers produced by cosmic rays and by gamma rays at TeV energies, using CORSIKA simulations. This method tries to solve the dominant hadron flux background problem when looking for gamma-ray signals measured by different experiments. The results of this work can be applied to the study of Gamma-Ray Bursts (GRBs). GRBs emit very energetic photons, which after interacting in the Earth's atmosphere, produce a large detectable electromagnetic cascade of secondary particles. The procedure will be to simulate events produced by photons, the signal, and protons, the most abundant cosmic-ray background. We extract several parameters from fitting particle air-shower longitudinal profiles, characterizing the simulated showers. Some of the most important _t parameters are the shower maximum (Xmax), the width of the shower FWHM, the asymmetry parameter, the maximum number of particles Nmax and the shower start Xstart. There are different experiments using water Cherenkov tanks and fluorescence detectors which can measure these shower parameters. We tested two methods. The first relies on simple cuts, while the second is based on a multivariate analysis using the TMVA package, which improves individual cuts. The first method was applied to single simulated energies of 102, 103, 104 and 105 GeV to find adequate cuts. We found that Xmax, FWHM, Xstart and Nmax depend on the energy. Later we applied these energy-dependent cuts and other fixed cuts to a realistic sample, which consists of 104 signal events (photons) and 106 background events (protons) covering an energy range from 102 to 105 GeV with different spectra. Moreover, we introduced an energy smearing to simulate a detector energy reconstruction efficiency. The obtained result leaves 54% signal events and 12% background events. Applying the multivariate analysis TMVA, we found that the Boosted Decision Trees (BDT) method was the best for distinguishing signal from background. The result for a similar signal efficiency was 0:7% of background events. Finally using tighter cuts on the BDT to improve the significance results in 1 photon event for every 1000 protons. Given the initial ux proportion, it means a 103 background rejection capability. Thus the feasibility of gamma/hadron separation requires further improvement.
Trabajo de investigación
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Lacki, Brian Cameron. "Cosmic Rays in Star-Forming Galaxies." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1313437011.
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吳文謙 and Man-him Ng. "Searching for gamma-ray signals form pulsars and periodic signals fromthe galactic gamma-ray sources." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31213509.
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Ng, Man-him. "Searching for gamma-ray signals form pulsars and periodic signals from the galactic gamma-ray sources /." Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19667942.
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Chadwick, Mary Paula. "Very high energy cosmic gamma rays from radio and X-ray pulsars." Thesis, Durham University, 1987. http://etheses.dur.ac.uk/6720/.
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This thesis is concerned with the detection of very high energy cosmic gamma-rays from isolated pulsars and X-ray binary sources using the atmospheric Cerenkov technique. A general introduction to gamma ray detection techniques is followed by adscription of the properties of atmospheric Cerenkov radiation and a discussion of the principles of the atmospheric Cerenkov technique. The Mark I and Mark II gamma-ray telescopes operated in Dugway, Utah by the University of Durham between 1981 and 1984 are briefly described. There follows a discussion of the results from observations at many different wavelengths of Cygnus X-3. This object was observed by the Durham group between 1981 and 1983 in Dugway Utah and also in Durham during autumn 1985. The detection in the Dugway data of the 4.8 hr X-ray period and the possible detection of a19.2 day intensity variation are considered. The discovery of a 12.59 ms pulsar in data taken on Cygnus X-3 in 1983 is described. Evidence is presented which suggests this periodicity is also present at a weaker level in earlier data and also in the data taken in Durham in 1985.Results from observations of PSR1937+21 , PSR1953+29and six radio pulsars , are presented. The design and construction of the Mark III telescope, now operating in Narrabri , N.S.W. , is described in detail. Preliminary results from observations with the Mark III telescope of three objects, LMC X-4, the Vela pulsar and CentaurusX-3, are presented, with particular reference to periodicities inherent in the sources. An observation of the supernova in the Large Magellanic Cloud is discussed. A brief discussion of the mechanisms by which V.H.E. gamma-rays may be produced in isolated pulsars and X-ray binary pulsars is given, followed by a description of the future prospects for the Mark III and Mark IV telescopes.
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James, Kory T. "High energry gamma-ray source search with SPASE-2." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 65 p, 2007. http://proquest.umi.com/pqdweb?did=1397914891&sid=16&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Giller, Graham L. "The construction and analysis of a whole-sky map using underground muons." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.386589.
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Seglar-Arroyo, Monica. "Studying the origin of cosmic-rays : Multi-messenger studies with very-high-energy gamma-ray instruments." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS260.
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Les phénomènes explosifs qui se produisent dans l'Univers à haute énergie sont capables d'accélérer les particules jusqu'aux énergies les plus élevées. Ces processus produisent des particules secondaires de nature différente, c'est-à-dire des photons et des neutrinos. Dans des cas particuliers, ces événements induisent des perturbations sur l'espace-temps, c'est-à-dire des ondes gravitationnelles détectables par des interféromètres sur Terre. La combinaison des informations complémentaires fournies par ces messagers cosmiques peuvent permettre de répondre à des questions ouvertes en astrophysique. Parmi les événements les plus violents qui produisent de tels signaux figurent la fusion des deux objets les plus denses, comme les étoiles à neutrons et les trous noirs ou l'activité accréatrice dans les galaxies sur un trou noir supermassif. Dans ce travail, nous nous concentrons sur les photons à très haute énergie que produisent ces événements extrêmes, et sur la connexion avec les autres contreparties, afin de fournir une image globale multi-messagers qui permet l'étude des mécanismes physiques en place. Les défis inhérents à l'astronomie multi-messager dans le domaine temporel, ce qui implique un effort mondial coordonné et simultané entre les installations et les disciplines astronomiques, sont discutés et abordés. Une nouvelle stratégie d'observation optimisée du suivi de l'eau souterraine pour les petits et moyens instruments de FoV comme le H.E.S.S. et le futur CTA, capable d'apporter une réponse rapide aux alertes, qui prend en compte les risques caractéristiques de l'événement GW et maximise les chances de détecter la contrepartie électromagnétique, sera présentée. Cette stratégie s'est avérée fructueuse lors d'observations de suivi avec les télescopes H.E.S.S., et en particulier dans le cas de la première detection de la fusion d'une binaire d'étoiles à neutrons, GW170817. Dans le cadre du réseau AMON, une analyse multi-messagers qui combine des événements d'ondes gravitationnelles avec des données HAWC a été développée dans le but d'identifier les coïncidences astrophysiques à partir d'événements indépendants. De plus, la découverte par H.E.S.S. en très hautes énergies du noyau galactique actif OT 081, lors d'un état de flux élevé en juillet 2016, sera présentéeThe explosive phenomena occurring in the high-energy Universe are able to accelerate particles up to the highest energies. These processes produce secondary particles of different nature, i.e. photons and neutrinos. In special cases, these events induce perturbations on the space-time, i.e. gravitational waves detectable by interferometers on Earth. The combination and the complementary information provided by these cosmic messengers may allow to answer open questions in astrophysics, as the origin of cosmic rays. Amongst the most violent events producing such signals are the merge of the two densest objects, as neutron stars and black holes or the accretion activity in galaxies onto a supermassive black hole. In this work, we focus on the very-high energy photons that these extreme events produce, and the connection with the other counterparts, in order to provide a broad multi-messenger picture which enables the study of the physical mechanisms in place. The challenges inherent to time-domain multi-messenger astronomy are discussed and tackled, which involves simultaneous coordinated worldwide effort across facilities and astronomical disciplines. A novel, optimized GW follow-up observation strategy for small/mid- FoV instruments as H.E.S.S. and the future CTA, able to perform a rapid response to alerts, which considers the characteristics of the GW event and maximizes the chances to detect the electromagnetic counterpart will be presented. This strategy was proven successful in follow-up observations with the H.E.S.S. telescopes and in particular in the case of the first ever detected binary neutron star merger, GW170817. In the context of the AMON network, a multi-messenger analysis that combines gravitational wave events with HAWC data, with the aim to identify astrophysical coincidences out of independent events, has been developed. In addition, the discovery by H.E.S.S. in very-high energies of the active galactic nucleus OT 081, during a flaring episode in July 2016, will be presented
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Venter, Christo. "Millisecond pulsars and pulsar wind nebulae as sources of gamma rays and cosmic rays / C. Venter." Thesis, North-West University, 2008. http://hdl.handle.net/10394/2067.
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Smith, Nigel James Telfer. "A search for ultra high energy gamma ray sources from the South Pole." Thesis, University of Leeds, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.291023.
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曾熙旻 and Hei-man Tsang. "Simulations and software developments for cosmic-ray and particle physics experiments in underground laboratories." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2007. http://hub.hku.hk/bib/B39557030.
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Guberman, Daniel Alberto. "MAGIC observations with bright Moon and their application to measuring the VHE gamma-ray spectral cut-off of the PeVatron candidate Cassiopeia A." Doctoral thesis, Universitat Autònoma de Barcelona, 2018. http://hdl.handle.net/10803/664122.
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Los rayos cósmicos son núcleos atómicos que constantemente bombardean la Tierra. Está largamente aceptado que estos núcleos con energías de hasta ~3 PeV son de origen Galáctico. Pero aún no se sabe dónde en la Galaxia ni cómo son acelerados. Durante muchos años la hipótesis más popular ha sido que son acelerados en remanentes de supernova. En esta tesis presento los detalles de una serie de observaciones de la joven remanente de supernova Cassiopeia A, uno de los candidatos más prometedores a ser un Pevatrón, un sistema capaz de acelerar rayos cósmicos hasta energías de PeV. Las observaciones fueron realizadas con los telescopios MAGIC, que observan rayos gamma de muy alta energía (VHE, E > 50 GeV), entre Diciembre de 2014 y Octubre de 2016, adquiriendo 191 horas de datos buena calidad. Acumular una gran cantidad de horas de observación era indispensable para obtener una medida precisa del espectro y fue posible gracias a la posibilidad de extender el tiempo activo de MAGIC operando los telescopios bajo una luminosidad lunar intensa. Trabajé en la optimización de las observaciones con Luna en MAGIC, tanto en el momento de operar los telescopios como en la etapa del análisis de los datos. Abordo los detalles de este desarrollo y evaluó su rendimiento. Con más del 70 % de las horas obtenidas con la Luna presente en el cielo, he podido obtener el espectro más preciso hasta ahora de Cassiopeia A en VHE. Por primera vez se encuentra evidencia de un corte a E = 3,5 (+1,6\—1,0) stat (+0,8\−0,9) sys TeV en el espectro. El
modelado de dicho espectro sugiere que la mayoría de los rayos gamma emitidos
pueden ser atribuidos a una población de protones de muy alta energía con un
índice espectral de ~2.2 y un corte a ~10 TeV. Esto implica que, asumiendo que no hay una difusión significativa d elos rayos cósmicos en el entorno de la supernova, Cassiopeia A no puede ser un PeVatrón en este momento.Cosmic rays are atomic nuclei that are constantly bombarding the Earth. It is widely accepted that these nuclei with energies up to ~3 PeV are of Galactic origin. But the question about where in the Galaxy and how they are accelerated still remains unanswered. For several years the most popular hypothesis has been that they are accelerated in supernova remnants. In this thesis I present the details of a deep observation campaign on the young supernova remnant Cassiopeia A, one of the most promising candidates to be a PeVatron, a system capable of accelerating cosmic rays up to PeV energies. The observations were performed with the MAGIC telescopes, that observe very high energy (VHE, E > 50 GeV) gamma rays, between December 2014 and October 2016, acquiring 191 hours of good-quality data. Accumulating a large amount of observation hours was indispensable to obtain a precise measurement of the spectrum and it was possible thanks to the possibility of extending the MAGIC duty cycle by operating the telescopes under bright moonlight. I worked in the optimization of moonlight observations with MAGIC, both during the operation of the telescopes and at the data analysis stage. I discuss the details of these developments and the resulting performance. With more than 70% of the data obtained under moonlight, I was able to obtain the most precise spectrum of Cassiopeia A to date at VHE. The obtained spectrum shows for the rst time 4:9 evidence of a cut-o at E = 3,5 (+1,6\—1,0) stat (+0,8\−0,9) sys TeV. The modelling of the spectrum suggests that the bulk of the gamma-rays emitted can be attributed to a population of high-energy protons with spectral index ~2.2 and energy cuto at ~10 TeV. This implies that, assuming there is no signicant cosmic-ray diusion, Cassiopeia A cannot be a PeVatron at its present age.
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Siemens, Xavier. "Gravitational waves and cosmic strings /." Thesis, Connect to Dissertations & Theses @ Tufts University, 2002.
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Thesis (Ph.D.)--Tufts University, 2002.Adviser: Alexander Vilenkin. Submitted to the Dept. of Physics. Includes bibliographical references (leaves 95-98). Access restricted to members of the Tufts University community. Also available via the World Wide Web;
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Federici, Simone. "Gamma-ray studies of the young shell-type SNR RX J1713.7-3946." Phd thesis, Universität Potsdam, 2014. http://opus.kobv.de/ubp/volltexte/2014/7173/.
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One of the most significant current discussions in Astrophysics relates to the origin of high-energy cosmic rays. According to our current knowledge, the abundance distribution of the elements in cosmic rays at their point of origin indicates, within plausible error limits, that they were initially formed by nuclear processes in the interiors of stars. It is also believed that their energy distribution up to 1018 eV has Galactic origins. But even though the knowledge about potential sources of cosmic rays is quite poor above „ 1015 eV, that is the “knee” of the cosmic-ray spectrum, up to the knee there seems to be a wide consensus that supernova remnants are the most likely candidates. Evidence of this comes from observations of non-thermal X-ray radiation, requiring synchrotron electrons with energies up to 1014 eV, exactly in the remnant of supernovae. To date, however, there is not conclusive evidence that they produce nuclei, the dominant component of cosmic rays, in addition to electrons.
In light of this dearth of evidence, γ-ray observations from supernova remnants can offer the most promising direct way to confirm whether or not these astrophysical objects are indeed the main source of cosmic-ray nuclei below the knee. Recent observations with space- and ground-based observatories have established shell-type supernova remnants as GeV-to- TeV γ-ray sources. The interpretation of these observations is however complicated by the different radiation processes, leptonic and hadronic, that can produce similar fluxes in this energy band rendering ambiguous the nature of the emission itself.
The aim of this work is to develop a deeper understanding of these radiation processes from a particular shell-type supernova remnant, namely RX J1713.7–3946, using observations of the LAT instrument onboard the Fermi Gamma-Ray Space Telescope. Furthermore, to obtain accurate spectra and morphology maps of the emission associated with this supernova remnant, an improved model of the diffuse Galactic γ-ray emission background is developed. The analyses of RX J1713.7–3946 carried out with this improved background show that the hard Fermi-LAT spectrum cannot be ascribed to the hadronic emission, leading thus to the conclusion that the leptonic scenario is instead the most natural picture for the high-energy γ-ray emission of RX J1713.7–3946. The leptonic scenario however does not rule out the possibility that cosmic-ray nuclei are accelerated in this supernova remnant, but it suggests that the ambient density may not be high enough to produce a significant hadronic γ-ray emission.
Further investigations involving other supernova remnants using the improved back- ground developed in this work could allow compelling population studies, and hence prove or disprove the origin of Galactic cosmic-ray nuclei in these astrophysical objects. A break- through regarding the identification of the radiation mechanisms could be lastly achieved with a new generation of instruments such as CTA.Eine der gegenwärtigen bedeutendsten geführten Diskussionen in der Astrophysik bezieht sich auf den Ursprung der hochenergetischen Kosmischen Strahlung. Nach unserem heutigen Verständnis weist die am Ort des Ursprungs elementare Zusam- mensetzung der Kosmischen Strahlung darauf hin, dass diese zu Beginn mittels nuklearer Prozesse im Inneren von Sternen gebildet wurde. Weiterhin wird ange- nommen, dass die Kosmische Strahlung bis 1018 eV galaktischen Ursprungs ist. Auch wenn das Verständnis über die potentiellen Quellen der Kosmischen Strahlung ober- halb von 1015 eV, dem sogenannten „Knie“ des Spektrums der Kosmischen Strah- lung, lückenhaft ist, so liegt doch der Konsens vor, dass Supernovaüberreste (SNR) die wahrscheinlichsten Quellen für Energien bis 1015 eV sind. Unterstützt wird die- ser Sachverhalt durch Beobachtungen von nichtthermischer Röntgenstrahlung von SNR, deren Emission Elektronen mit Energien bis zu 1014 eV erfordern. Jedoch gibt es bis heute keinen überzeugenden Beweis, dass SNR zusätzlich zu den Elektronen auch Atomkerne, die den dominierenden Anteil in der Kosmischen Strahlung bilden, beschleunigen. Trotz fehlender überzeugender Beweise ermöglichen nun Beobachtungen von SNR im γ-Strahlungsbereich einen vielversprechenden Weg zur Aufklärung der Fra- ge, ob diese astrophysikalischen Objekte in der Tat die Hauptquelle der Kosmischen Strahlung unterhalb des Knies sind. Kürzlich durchgeführte Beobachtungen im Welt- raum und auf der Erdoberfläche haben zu der Erkenntnis geführt, dass schalenartige SNR γ-Strahlung im GeV- und TeV-Bereich emittieren. Die Interpretation dieser Beobachtungen ist jedoch schwierig, da sowohl Atomkerne als auch Elektronen im betrachteten Energiebereich zu ähnlichen γ-Emissionen führen. Dadurch wird die eindeutige Identifizierung der Emission als das Resultat hadronischer oder leptoni- scher Emissionsprozesse erschwert. Das Ziel dieser Arbeit ist es, am Beispiel des schalenartigen SNR RX J1713.7- 3946 ein tieferes Verständnis über die Strahlungsprozesse zu erhalten, indem vom γ-Weltraumteleskop Fermi durchgeführte Beobachtungen analysiert werden. Um ge- naue Spektren und die Ausdehnung der Region der Emission zu erhalten, wird ein verbessertes Modell für die diffuse galaktische γ-Hintergrundstrahlung entwickelt. Die mit diesem verbesserten Hintergrund durchgeführte Analyse von RX J1713.7- 3946 zeigt, dass das vom Fermi-Satelliten beobachtete Spektrum nicht dem hadro- nischen Szenario zugeschrieben werden kann, sodass das leptonische Szenario für die γ-Emissionen von diesem SNR verantwortlich ist. Das leptonische Szenario schließt jedoch nicht die Möglichkeit aus, dass auch Atomkerne in diesem SNR beschleu- nigt werden. Aber es deutet darauf hin, dass die umgebende Teilchendichte nicht ausreichend hoch genug ist, um zu einer signifikanten hadronischen γ-Emission zu führen. Weitere Untersuchungen, die andere SNR in Kombination mit dem hier ent- wickelten verbesserten Modell der Hintergrundstrahlung beinhalten, können Popu- lationsstudien erlauben. Dies könnte klären, ob die SNR tatsächlich die Quellen der galaktischen Kosmischen Strahlung sind. Ein Durchbruch bezüglich der Identi- fikation des Strahlungsmechanismus könnte auch durch eine neue Generation von Beobachtungsinstrumenten, wie das Cherenkov Telescope Array, erreicht werden.
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Tummey, Steven Peter. "A search for diffuse and point source emission of UHE gamma rays using muon content selected EAS." Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336196.
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Prosser, David Clarke. "A search for gamma-ray emission at energies greater than 10'1'4eV from Cygnus X-3 and eight other candidate sources." Thesis, University of Leeds, 1991. http://etheses.whiterose.ac.uk/21077/.
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The discovery of cosmic rays with energies greater than 1014e V has posed a question that has not, as yet, been answered: where are particles accelerated to such high energies? A possible answer to this question came in 1983 with the claim made by Samorski and Stamm of an excess number of cosmic rays from the direction of Cygnus X-3. This result was then confirmed by Lloyd-Evans et al. (1983). The excess was taken to be gamma-rays as the galactic magnetic fields result in charged particles being greatly deflected. These claims led to the birth of Pe V gamma-ray astronomy and the building of numerous instruments designed to search for point sources of Pe V gamma-ray emission. One such instrument was the GREX extensive air shower array built at Haverah Park which began collecting data in March 1986. This thesis describes the GREX array and the methods of analysis used to reconstruct the size and arrival direction of the incident cosmic rays from the detected air showers. The methods used to search for potential point sources are then described. These methods have been applied to data recorded by the GREX array between 6 March 1986 and 18 December 1990. Particular attention has been paid to Cygnus X-3 and 8 other candidate sources. No evidence for steady, periodic or sporadic emission has been found for any of the 9 potential sources. In addition, an all-sky survey has failed to discover any unknown point sources of emission in the Northern sky. Observations made by other groups of Cygnus X-3 and the 8 other candidate sources at 10 12 and 10 15 eV are discussed. Cassiday et al. (1989) claimed to have observed an excess of cosmic rays from Cygnus X-3 with energies greater than Sx10 17 eV. A claimed confirmation of this result was made by the Akeno group (Teshima et al. 1990). A search for emission of 5x10 17 eV cosmic rays from Cygnus X-3 has been made using data from the Haverah Park 12km 2 array and is described in this thesis. The upper limit to the flux from Cygnus X-3 in this search is significantly lower than the claimed flux, even during periods of contemporaneous observations.
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Zimmer, Stephan. "Searching for Gamma Rays from Galaxy Clusters with the Fermi Large Area Telescope : Cosmic Rays and Dark Matter." Licentiate thesis, Stockholms universitet, Fysikum, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-96231.
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In this licentiate thesis, I report a search for GeV γ rays towards the location of Galaxy clusters. I mainly discuss the results of a search for cosmic-ray (CR) induced γ-ray emission but also briefly elaborate on a related study, searching for Dark Matter (DM)-induced γ-ray emission from Galaxy clusters. In addition, I provide a detailed discussion on the analysis tools that were used and discuss some additional tests that are not included in the papers this licentiate thesis is based on. In a comprehensive search almost covering the entire sky, we find no statistically significant evidence for either DM or CR induced γ rays from galaxy clusters. Thus we report upper limits on CR quantities that exclude emission scenarios in which the maximum hadronic injection efficiency is larger than 21% and associated limits on the maximum CR-to-thermal pressure ratio, <XCR>. In addition, we update previous flux upper limits given a new set of modeling and taking the source extension into account. For a DM masses below 100 GeV, we exclude annihilation cross sections above ∼ 10−24 cm3 s−1 into bb. For decaying DM, we exclude decay times lower than 1027 s over the mass range of 20 GeV– 2 TeV.
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Buckman, Benjamin Jerome. "Cosmic-Ray Emission as a Window into Extragalactic Environments: Starburst Galaxies & Blazars." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595554171852752.
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Edwards, Peter J. "A study of the muon content of EAS initiated by the UHE gamma-ray emission from Cygnus X-3." Thesis, University of Nottingham, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.238238.
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Peron, Giada [Verfasser], and Felix [Akademischer Betreuer] Aharonian. "Probing the Spatial and Spectral Distribution of Galactic Cosmic Rays with High-Energy Gamma-Rays / Giada Peron ; Betreuer: Felix Aharonian." Heidelberg : Universitätsbibliothek Heidelberg, 2021. http://d-nb.info/1225938627/34.
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Zimmer, Stephan. "Observations of nearby Galaxy Clusters with the Fermi Large Area Telescope : Towards the first Gamma Rays from Clusters." Doctoral thesis, Stockholms universitet, Fysikum, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-121592.
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Galaxy clusters are the most massive bound systems known in the Universe and are believed to have formed through large scale structure formation. They host relativistic cosmic-ray (CR) populations and are gravitationally bound by large amounts of Dark Matter (DM), both providing conditions in which high-energy gamma rays may be produced either via CR interactions with the intracluster medium or through the annihilation or decay of DM particles. Prior to the launch of the Fermi satellite, predictions were optimistic that these sources would be established as γ-ray-bright objects by observations through its prime instrument, the Large Area Telescope (LAT). Yet, despite numerous efforts, even a single firm cluster detection is still pending. This thesis presents a number of studies based on data taken by the LAT over its now seven year mission aiming to discover these γ rays. Using a joint likelihood technique, we study the γ-ray spectra of a sample of nearby clusters searching for a CR-induced signal due to hadronic interactions in the intracluster medium. While we find excesses in some individual targets, we attribute none to the cluster. Hence, we constrain the maximum injection efficiency of hadrons being accelerated in structure formation shocks and the fraction of CR-to-thermal pressure. We also perform a refined search targeting the Coma cluster specifically due to its large variety of existing observations in other wavebands. In the latter case we find weak indications of an excess which however falls below the detection threshold. Because the cluster emission we consider is inherently extended, we need to take into account the imperfect modeling of the foreground emission, which may be particularly difficult such as is the case with the Virgo cluster. Here, we assess the systematics associated with the foreground uncertainties and derive limits based on an improved background model of the region. For the first time we derive limits on the γ-ray flux from CR and DM-interactions in which we take into account the dynamical state of the system. For DM we also include the contribution from substructure. The DM domain is further explored by searching for line-like features as they arise from the annihilation of DM into two photons in a large sample of clusters, including Virgo and Coma. Finding no evidence for γ-ray lines, we derive limits on the DM annihilation cross section that are roughly a factor 10 (100) above that derived from observations of the galactic center assuming an optimistic (conservative) scenario regarding the boost due to DM substructure.At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: Submitted.
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Giesen, Gaelle. "Dark Matter Indirect Detection with charged cosmic rays." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112160/document.
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Les preuves pour l'existence de la matière noire (MN), sous forme d'une particule inconnue qui rempli les halos galactiques, sont issues d'observations astrophysiques et cosmologiques: son effet gravitationnel est visible dans les rotations des galaxies, des amas de galaxies et dans la formation des grandes structures de l'univers. Une manifestation non-gravitationnelle de sa présence n'a pas encore été découverte. L'une des techniques les plus prometteuse est la détection indirecte de la MN, consistant à identifier des excès dans les flux de rayons cosmiques pouvant provenir de l'annihilation ou la désintégration de la MN dans le halo de la Voie Lactée. Les efforts expérimentaux actuels se focalisent principalement sur une gamme d'énergie de l'ordre du GeV au TeV, où un signal de WIMP (Weakly Interacting Massive Particles) est attendu. L'analyse des mesures récentes et inédites des rayons cosmiques chargés (antiprotons, électrons et positrons) et leurs émissions secondaires et les améliorations des modèles astrophysiques sont présentées.Les données de PAMELA sur les antiprotons contraignent l'annihilation et la désintégration de la MN de manière similaire (et même légèrement meilleurs) que les contraintes les plus fortes venant des rayons gamma, même dans le cas où les énergies cinétiques inférieures à 10 GeV sont écartées. En choisissant des paramètres astrophysiques différents (modèles de propagation et profils de MN), les contraintes peuvent changer d'un à deux ordres de grandeur. Pour exploiter la totalité de la capacité des antiprotons à contraindre la MN, des effets précédemment négligés sont incorporés et se révèlent être importants dans l'analyse des données inédites de AMS-02 : ajouter les pertes d'énergie, la diffusion dans l'espace des moments et la modulation solaire peut modifier les contraintes, même à de hautes masses. Une mauvaise interprétation des données peut survenir si ces effets ne sont pas pris en compte. Avec les flux de protons et d'hélium exposé par AMS-02, le fond astrophysique et ces incertitudes du ratio antiprotons sur protons sont réévalués et comparés aux données inédites de AMS-02. Aucune indication pour un excès n'est trouvé. Une préférence pour un halo confinant plus large et une dépendance en énergie du coefficient de diffusion plus plate apparaissent. De nouvelles contraintes sur l'annihilation et la désintégration de la MN sont ainsi dérivés.Les émissions secondaires des électrons et des positrons peuvent aussi contraindre l'annihilation et la désintégration de la MN dans le halo galactique : le signal radio dû à la radiation synchrotron des électrons et positrons dans le champs magnétique galactique, les rayons gamma des processus de bremsstrahlung avec le gas galactique et de Compton Inverse avec le champs radiatif interstellaire sont considérés. Différentes configurations de champs magnétique galactique et de modèles de propagation et des cartes de gas et de champs radiatif interstellaire améliorés sont utilisées pour obtenir des outils permettant le calculs des émissions synchrotrons et bremsstrahlung venant de MN de type WIMP. Tous les résultats numériques sont incorporés dans la dernière version du Poor Particle Physicist Coookbook for DM Indirect Detection (PPPC4DMID).Une interprétation d'un possible excès dans les données de rayons gamma de Fermi-LAT au centre galactique comme étant dû à l'annihilation de MN en canaux hadronique et leptonique est analysée. Dans une approche de messagers multiples, le calcul des émissions secondaires est amélioré et se révèle être important pour la détermination du spectre pour le canal leptonique. Ensuite, les limites provenant des antiprotons sur l'annihilation en canal hadronique contraignent sévèrement l'interprétation de cet excès comme étant dû à la MN, dans le cas de paramètres de propagation et de modulation solaire standards. Avec un choix plus conservatif de ces paramètres elles s'assouplissent considérablementOverwhelming evidence for the existence of Dark Matter (DM), in the form of an unknownparticle filling the galactic halos, originates from many observations in astrophysics and cosmology: its gravitational effects are apparent on galactic rotations, in galaxy clusters and in shaping the large scale structure of the Universe. On the other hand, a non-gravitational manifestation of its presence is yet to be unveiled. One of the most promising techniques is the one of indirect detection, aimed at identifying excesses in cosmic ray fluxes which could possibly be produced by DM annihilations or decays in the Milky Way halo. The current experimental efforts mainly focus in the GeV to TeV energy range, which is also where signals from WIMPs (Weakly Interacting Massive Particles) are expected. Focussing on charged cosmic rays, in particular antiprotons, electrons and positrons, as well as their secondary emissions, an analysis of current and forseen cosmic ray measurements and improvements on astrophysical models are presented. Antiproton data from PAMELA imposes contraints on annihilating and decaying DM which are similar to (or even slightly stronger than) the most stringent bounds from gamma ray experiments, even when kinetic energies below 10 GeV are discarded. However, choosing different sets of astrophysical parameters, in the form of propagation models and halo profiles, allows the contraints to span over one or two orders of magnitude. In order to exploit fully the power of antiprotons to constrain or discover DM, effects which were previously perceived as subleading turn out to be relevant especially for the analysis of the newly released AMS-02 data. In fact, including energy losses, diffusive reaccelleration and solar modulation can somewhat modify the current bounds, even at large DM masses. A wrong interpretation of the data may arise if they are not taken into account. Finally, using the updated proton and helium fluxes just released by the AMS-02 experiment, the astrophysical antiproton to proton ratio and its uncertainties are reevaluated and compared to the preliminarly reported AMS-02 measurements. No unambiguous evidence for a significant excess with respect to expectations is found. Yet, some preference for thicker halos and a flatter energy dependence of the diffusion coefficient starts to emerge. New stringed constraints on DM annihilation and decay are derived. Secondary emissions from electrons and positrons can also be used to constrain DM annihilation or decay in the galactic halo. The radio signal due to synchrotron radiation of electrons and positrons on the galactic magnetic field, gamma rays from bremsstrahlung processes on the galactic gas densities and from Inverse Compton scattering processes on the interstellar radiation field are considered. With several magnetic field configurations, propagation scenarios and improved gas density maps and interstellar radiation field, state-of-art tools allowing the computaion of synchrotron and bremssttrahlung radiation for any WIMP DM model are provided. All numerical results for DM are incorporated in the release of the Poor Particle Physicist Coookbook for DM Indirect Detection (PPPC4DMID). Finally, the possible GeV gamma-ray excess identified in the Fermi-LAT data from the Galactic Center in terms of DM annihilation, either in hadronic or leptonic channels is studied. In order to test this tantalizing interprestation, a multi-messenger approach is used: first, the computation of secondary emisison from DM with respect to previous works confirms it to be relevant for determining the DM spectrum in leptonic channels. Second, limits from antiprotons severely constrain the DM interpretation of the excess in the hadronic channel, for standard assumptions on the Galactic propagation parameters and solar modulation. However, they considerably relax if more conservative choices are adopted
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MacRae, John Hamish Kenneth. "The detection of very high energy cosmic gamma rays using the atmospheric Cerenkov technique." Thesis, Durham University, 1985. http://etheses.dur.ac.uk/7854/.
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This thesis is concerned with the detection of very high energy cosmic gamma rays using the atmospheric Cerenkov technique. A general introduction to gamma ray detection techniques is followed by a detailed discussion of the principles of the atmospheric Cerenkov technique and the history of its use prior to this work. The design and operation of the University of Durham facility in Dugway, Utah is described in depth. Monte Carlo computer simulations have been developed to assist in both the understanding of the equipment and the analysis of the results for the Durham facility. The variation of the response of the array with zenith angle and detector threshold has been investigated and the aperture function of a single telescope calculated. The latter has been found to be a complicated function of both zenith angle and detector threshold. Computer simulations have also been developed to aid in the design of a camera to record two-dimensional Cerenkov light images from small extensive air showers, and to provide a means of testing analysis routines; these are discussed. The camera is located at the F.L. Whipple Observatory in Arizona. The techniques employed in the analysis of data recorded by the Dugway facility are discussed, and a computer package developed to aid in the routine aspects of the analysis is described. Results of observations from two sources, Cygnus X-3 and PSR0531, are presented, with particular reference to periodicities inherent in the sources and to bursts of gamma ray emission. The discussion of the results includes a review of the various models which have been proposed for Cygnus X-3.
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Samuelsson, Filip. "Multi-messenger emission from gamma-ray bursts." Licentiate thesis, KTH, Partikel- och astropartikelfysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-273383.
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Multi-messenger astronomy is a very hot topic in the astrophysical community. A messenger is something that carries information. Different astrophysical messenger types are photons, cosmic rays, neutrinos, and gravitational waves. They all carry unique and complementary information to one another. The idea with multi-messenger astronomy is that the more different types of messengers one can obtain from the same event, the more complete the physical picture becomes. In this thesis I study the multi-messenger emission from gamma-ray bursts (GRBs), the most luminous events known in the Universe. Specifically, I study the connection of GRBs to extremely energetic particles called ultra-high-energy cosmic rays (UHECRs). UHECRs have unknown origin despite extensive research. GRBs have long been one of the best candidates for the acceleration of these particles but a firm connection is yet to be made. In Paper I and Paper II, we study the possible GRB-UHECR connection by looking at the electromagnetic radiation from electrons that would also be accelerated together with the UHECR. My conclusion is that the signal from these electrons does not match current GRB observation, disfavoring that a majority of UHECRs comes from GRBs.”Multi-messenger astronomy” (mångbudbärarastronomi, fri översättning) är ett väldigt aktuellt område inom astrofysiken just nu. En meddelare är någonting som bär på information. Olika meddelartyper inom astrofysiken är fotoner, kosmisk strålning, neutriner och gravitations vågor. Dessa har alla unik och olika typ av information som kompletterar varandra. Idén bakom multi-meddelare-astronomi är att ju fler olika meddelartyper vi kan upptäcka från samma event, desto mer komplett blir vår fysikaliska tolkning. I denna avhandling studerar jag multi-meddelare emission från gammablixtar (GRBs), de mest ljusstarka företeelser vi känner till i Universum. Mer specifikt, så studerar jag kopplingen mellan GRBs och ultraenergetisk kosmisk strålning (UHECRs). Ursprunget till UHECRs är fortfarande okänt trots långt pågående forskning. GRBs har länge varit en av de mest lovande accelerationskandidaterna men än så länge finns inga fasta bevis. I Paper I och Paper II studerar vi den möjliga GRB-UHECR kopplingen genom att studera den elektromagnetiska strålningen från elektronerna som även de skulle bli accelererade tillsammans med UHECRs. Min slutsats är att strålningen från elektronerna inte matchar observationer från GRBs, vilket talar emot att en majoritet av UHECRs kommer från GRBs.
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Galindo, Fernández Daniel. "Study of the extreme gamma-ray emission from Supernova Remnants and the Crab Pulsar." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/663414.
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In our Galaxy, supernova remnants and pulsars are the two most numerous populations of non-thermal objects. The goal of this thesis is to study the extreme gamma-ray emission from these two astrophysical objects with Fermi -LAT and MAGIC. In particular, supernova remnants Cassiopeia A and SNR G24.7+0.6 and the Crab pulsar.
Cassiopeia A, one of the historical supernova remnants and the prime candidate of its class to be a PeVatron accelerator, has been discarded as so since we provided the first measurement of a turn-off in the gamma-ray spectrum at 3 TeV, implying the emission observed is produced by the decay of neutral pions, produced in proton- proton interactions of a parent population of accelerated protons with an energy cut-off at about 10TeV. Such a maximum energy of accelerated cosmic rays in Cassiopeia A falls short to explain the high energy end ( PeV) of the Galactic cosmic ray spectrum. Considering that Cassiopeia A was the main PeVatron candidate, the results obtained in this work challenge the existence of supernova remnants as galactic Pevatrons and therefore the popular conviction that supernova remnants are the main source of Galactic cosmic ray up to the knee.
In the case of SNR G24.7+0.6, the remnant is evolving in a dense medium and might be interacting with the CO-rich surrounding. The observations performed allowed us to detect for the first time the counterpart of the radio emission, MAGIC J1835–069, from 60MeV up to 5TeV. This very high energy emission results from proton-proton interactions between the runaway protons from the supernova remnant and a nearby molecular cloud. These observations of the field of view of SNR G24.7+0.6, also resulted in the detection of another new source, MAGIC J1837–073, that is likely to be associated with a stellar cluster as suggested by its localization in a region rich in molecular content and crowded of sources. The total energy obtained in accelerated protons can be explained assuming a quasi-continuous injection of cosmic rays during the cluster lifetime.
The second part of this thesis is focused on the study and understanding of the Crab pulsar, the young and most energetic pulsar in our galaxy. Observations carried out with MAGIC resulted in the first ever detection of very energetic pulsed emission from a pulsar, reaching up to about 1.5 TeV. Moreover, the light curve of the Crab above 400 GeV shows two peaks synchronized with those measured at lower energies. Such extremely energetic pulsed emission has to be produced by electrons with very high Lorentz factor scattering low energy photons in the vicinity of the light cylinder, either inside or outside of it. Currently, none of the postulated models is yet capable of reproducing at the same time the light curve and the spectral shape for both peaks above 400 GeV.Esta tesis tiene como objetivo el estudio de la emisión extrema de rayos gamma proveniente de remanentes de supernova y el pulsar del Cangrejo. Dos remanentes de supernova han sido observados tanto con Fermi, como con MAGIC; Cassiopeia A y SNR G24.7+0.6. Cassiopeia A, el principal candidato de su clase a revelarse como PeVatrón, ha sido descartado como tal, al haberse detectado un corte en el espectro de rayos gamma en torno a 3 TeV, lo cual implica que, la emisión observada es producida por el de- caimiento de piones neutros, originados en colisiones protón-protón por una población de protones que presenta un corte exponencial en su espectro en torno a una energía de 10 TeV. Esta energía máxima a la que son acelerados estos rayos cósmicos pone en serias dudas la existencia de remanentes de supernova que se comporten como PeVa- trones, y por tanto, la teoría de que éstos son la fuente principal de rayos cósmicos galácticos. En el caso de SNR G24.7+0.6, con las observaciones llevadas a cabo, hemos conseguido detectar por primera vez la contrapartida de la emisión radio a energías desde 60 MeV hasta 5 TeV, MAGIC J1835–069, producida por protones que escapan del remanente de supernova y que interaccionan con una nube molecular cercana. En estas mismas observaciones, hemos podido detectar otra fuente nueva, MAGIC J1837–073, la cual está asociada, muy probablemente, con un cumulo estelar tal y como sugiere su lo- calización. Su emisión puede ser explicada asumiendo una inyección casi continua de rayos cósmicos durante la totalidad de la vida estimada del cumulo estelar. Por otra parte, el estudio del púlsar del Cangrejo, llevado a cabo con MAGIC ha re- sultado en el descubrimiento de emisión pulsada hasta 1.5 TeV, refutando cualquiera de los modelos presentados hasta el momento. Además, la curva de luz que carac- teriza la emisión proveniente del púlsar por encima de 400 GeV, presenta dos picos sincronizados en fase con los picos hallados a energías más bajas. Esta emisión, ex- tremadamente energética, únicamente puede ser producida por electrones acelerados hasta factores de Lorentz muy altos en regiones cercanas al cilindro de luz, ya sea en su interior o en su exterior, y que posteriormente colisionan y transfieren su energía a fotones térmicos.
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Zeng, Houdun, Yuliang Xin, Siming Liu, J. R. Jokipii, Li Zhang, and Shuinai Zhang. "EVOLUTION OF HIGH-ENERGY PARTICLE DISTRIBUTION IN MATURE SHELL-TYPE SUPERNOVA REMNANTS." IOP PUBLISHING LTD, 2017. http://hdl.handle.net/10150/623101.
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Multi-wavelength observations of mature supernova remnants (SNRs), especially with recent advances in gamma-ray astronomy, make it possible to constrain energy distribution of energetic particles within these remnants. In consideration of the SNR origin of Galactic cosmic rays and physics related to particle acceleration and radiative processes, we use a simple one-zone model to fit the nonthermal emission spectra of three shell-type SNRs located within 2 degrees on the sky: RX J1713.7-3946, CTB 37B, and CTB 37A. Although radio images of these three sources all show a shell (or half-shell) structure, their radio, X-ray, and gamma-ray spectra are quite different, offering an ideal case to explore evolution of energetic particle distribution in SNRs. Our spectral fitting shows that (1) the particle distribution becomes harder with aging of these SNRs, implying a continuous acceleration process, and the particle distributions of CTB 37A and CTB 37B in the GeV range are harder than the hardest distribution that can be produced at a shock via the linear diffusive shock particle acceleration process, so spatial transport may play a role; (2) the energy loss timescale of electrons at the high-energy cutoff due to synchrotron radiation appears to be always a bit (within a factor of a few) shorter than the age of the corresponding remnant, which also requires continuous particle acceleration; (3) double power-law distributions are needed to fit the spectra of CTB 37B and CTB 37A, which may be attributed to shock interaction with molecular clouds.
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Fleischhack, Henrike. "Measurement of the iron spectrum in cosmic rays with the VERITAS experiment." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2017. http://dx.doi.org/10.18452/17691.
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Das Energiespektrum der kosmischen Strahlung bietet wichtige Hinweise auf ihren Ursprung und ihre Ausbreitung. Verschiedene Messtechniken müssen kombiniert werden, um den ganzen Energiebereich abdecken zu können: Direkte Messungen mit Teilchendetektoren bei niedrigen Energien sowie indirekte Messungen von Luftschauern bei hohen Energien. Dazu kommt die Messung von Photonen, hauptsächlich im GeV- und TeV-Bereich, die bei der Wechselwirkung von kosmischer Strahlung mit Materie oder elektromagnetischen Feldern entstehen. Im Folgenden werde ich zwei Studien dazu vorstellen, die beide auf Daten des abbildenden Tscherenkow-Teleskopes VERITAS beruhen. Erstens stelle ich eine Messung das Energiespektrums von Eisenkernen in der kosmischen Strahlung vor. Für die Bestimmung der Energie und Ankunftsrichtung der Primärteilchen benutze ich eine neuartige Template-Likelihood-Methode, die hier erstmals auf Eisenschauer angewendet wird. Zur Identifizierung der Eisenschauer benutze ich unter anderem das sogenannte direkte Tscherenkow-Licht, welches von geladenen Teilchen vor der ersten Wechselwirkung ausgestrahlt wird. Dazu kommt eine multivariate Klassifizierungsmethode, um den Verbleibenden Untergrund zu charakterisieren. Das so gemessene Energiespektrum von Eisen wird im Bereich von 20 TeV bis 500 TeV gut durch ein Potenzgesetz beschrieben. Zweitens beschreibe ich eine Suche nach Gammastrahlung oberhalb von 100 GeV von den drei Galaxien Arp 220, IRAS 17208-0014 und IC 342. Diese drei Galaxien haben hohe Sternentstehungsraten und daher viele Supernova-Überreste, welche kosmische Strahlung erzeugen. Diese wechselwirkt erwartungshalber mit den dichten Staubwolken in den Sternentstehungsgebieten und erzeugt Gammastrahlung. VERITAS konnte keine solche Gammastrahlung messen. Die daraus abgeleitete Höchstgrenze für die Luminosität schränkt theoretische Modelle der Erzeugung und Propagation von kosmischer Strahlung in der Galaxie Arp 220 ein.The energy spectrum of cosmic rays can provide important clues as to their origin and propagation. Different experimental techniques have to be combined to cover the full energy range: Direct detection experiments at lower energies and indirect detection via air showers at higher energies. In addition to detecting cosmic rays at Earth, we can also study them via the electromagnetic radiation, in particular gamma rays, that they emit in interactions with gas, dust, and electromagnetic fields near the acceleration regions or in interstellar space. In the following I will present two studies, both using data taken by the imaging air Cherenkov telescope (IACT) VERITAS. First, I present a measurement of the cosmic ray iron energy spectrum. I use a novel template likelihood method to reconstruct the primary energy and arrival direction, which is for the first time adapted for the use with iron-induced showers. I further use the presence of direct Cherenkov light emitted by charged primary particles before the first interaction to identify iron-induced showers, and a multi-variate classifier to measure the remaining background contribution. The energy spectrum of iron nuclei is well described by a power law in the energy range of 20 to 500 TeV. Second, I present a search for gamma-ray emission above 100 GeV from the three star-forming galaxies Arp 220, IRAS 17208-0014, and IC342. Galaxies with high star formation rates contain many young and middle-aged supernova remnants, which accelerate cosmic rays. These cosmic rays are expected to interact with the dense interstellar medium in the star-forming regions to emit gamma-ray photons up to very high energies. No gamma-ray emission is detected from the studied objects and the resulting limits begin to constrain theoretical models of the cosmic ray acceleration and propagation in Arp 220.
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Tsang, Hei-man. "Simulations and software developments for cosmic-ray and particle physics experiments in underground laboratories." Click to view the E-thesis via HKUTO, 2007. http://sunzi.lib.hku.hk/HKUTO/record/B39557030.
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Karlsson, Niklas. "Parametric Model for Astrophysical Proton-Proton Interactions and Applications." Doctoral thesis, Stockholm : Fysik, Kungliga Tekniska högskolan, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4524.
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Ng, Chun Yu. "Seeking the Light in the Dark: Quests for Identifying Dark Matter." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471363029.
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Reichardt, Candel Ignasi. "Search for gamma-ray emission from supernova remnants with the Fermi/LAT and MAGIC telescopes." Doctoral thesis, Universitat Autònoma de Barcelona, 2012. http://hdl.handle.net/10803/98414.
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Tibaldo, Luigi. "Diffuse γ-ray emission observed by the Fermi Large Telescope : massive stars, cosmic rays and the census of the interstellar medium in the Galaxy." Paris 7, 2011. http://www.theses.fr/2011PA077040.
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L'émission gamma diffuse Galactique provient des interactions des rayons cosmiques avec le gaz et le champ de rayonnement de l’énergie dans l'espace interstellaire. Elle représente la composante la plus brillante du ciel gamma de haute énergie, lequel est observé depuis 2008 avec une sensibilité et une résolution angulaire sans précédent par le Large Area Télescope (LAT) à bord du télescope spatial Fermi. L'émission diffuse Galactique ne constitue pas seulement un fond intense et structuré qui doit être modélisé pour étudier les sources individuelles ou les composantes diffuses plus faibles, mais elle peut être utilisée pour sonder l'environnement interstellaire de la Voie Lactée. Des études détaillées des observations gamma du LAT dans des régions spécifiques de la Galaxie locale et externe sont présentées. Les données LAT sont comparées à des traceurs multi longueurs d'onde du milieu interstellaire, dont les raies radio et millimétriques du gaz et l’émission et l'extinction des poussières. Les contraintes apportées par l'émission gamma sur le recensement du gaz interstellaire sont discutées. Le rapport X(CO)=N(H2)/'W/(CO) est déterminé dans plusieurs nuages. L'émission gamma révèle la présence un peu partout d'une phase sombre du gaz interstellaire qui ne brille pas à d'autres longueurs d'onde. D'autre part, l'émissivité trouvée par atome d'hydrogène sert à suivre la distribution des rayons cosmiques dans des endroits éloignés, non accessibles par des mesures directes. Les données LAT révèlent une bulle étendue d'émission gamma dure dans les 100 pc centraux de la région active de formation d'étoiles du CygneGalactic diffuse gamma-ray emission is produced by interactions of cosmic rays with interstellar gas and low-energy radiation fields is the brightest component of the high-energy gamma-ray sky, surveyed since 2008 with unprecedented sensitivity and angular resolution by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. Galactic diffuse emission constitutes not on bright and structured background which needs to be modeled in order to study individual sources and fainter diffuse components, but it can be used also as a probe of the interstellar environment of the Milky Way. We present in-depth studies of LAT \g-ray observations of selected regions in the local and outer Galaxy. LAT data are compared v multiwavelength tracers of the interstellar medium, including radio/mm-wave lines of gas and infrared emission/extinction from dust On one hand, we discuss the constraints provided by the gamma-ray data on the census of the interstellar gas. We determine the ratio X(CO)=N(H2)/W(CO) for several clouds and we also find evidence for an ubiquitous dark phase of interstellar gas which does not shine; at other wavelengths. On the other hand, we use the emissivity per hydrogen atom to infer the distribution of cosmic rays in distant locations not accessible by direct measurements. A remarkably hard and extended excess of gamma-rays is detected in the innermost 100 pc of the massive-star forming region in Cygnus
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Nakamura, Toshio, Kentarou Nagaya, Fusa Miyake, Kimiaki Masuda, 俊夫 中村, 健太朗 永冶, 芙沙 三宅, and 公明 増田. "炭素14と宇宙線変動 : 奈良時代の異変." 名古屋大学年代測定資料研究センター, 2013. http://hdl.handle.net/2237/20130.
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Anjos, Rita de Cássia dos. "Propagação de raios cósmicos extragaláticos." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-18082014-142550/.
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Recentemente, o Observatório Pierre Auger tem medido espectro de energia de Raios Cósmicos Ultra Energéticos (Ultra High Energy Cosmic Rays - UHECR) (E > 1019 eV) com grande acurácia. No entanto, o estudo de raios cósmicos ultra energéticos na Terra tem uma forte dependência do estudo de sua propagação no Universo. Neste trabalho, abordamos o estudo da propagação de raios cósmicos em diferentes aspectos. Núcleos em alta energia interagem com os campos de radiação no caminho da fonte à Terra. A interação mais importante é a fotodesintegração. Na primeira parte, implementamos de maneira analítica e numérica a solução da razão de fotodesintegração e fizemos uso da solução numérica em um programa de Monte Carlo. Mostramos soluções baseadas na parametrização das seções de choque por uma função Gaussiana e por uma função Lorenztiana. Comparamos nossos resultados com trabalhos prévios da literatura. O seguinte estudo mostrou que sob a hipótese de propagação quase-linear e utilizando várias distribuições de fontes no céu, a latitude do observatório: tem influência no fluxo total medido por um observatório; impõe um limite na capacidade de medida de anisotropia e tem um efeito negligenciável na medida do XMax. No terceiro estudo, um limite superior na integral do fluxo de raios gama em GeV-TeV é usado para obter um limite superior na luminosidade total de UHECR de fontes individuais. A correlação entre o limite superior na integral do fluxo de raios gama e o limite superior na luminosidade total de UHECR é estabelecida através do processo de cascatas de partículas geradas durante a propagação de raios cósmicos nos campos de radiação.Recently, the Pierre Auger Observatory has measured the energy spectrum of Ultra High Energy Cosmic Rays (UHECR) (E > 1019 eV) with an unprecedented accuracy. However, the study of ultra-high energy cosmic rays at Earth depends on the models used to describe the propagation of the particle in the Universe. In this work, we present a study of propagation of cosmic rays on different aspects. Nucleus at this high energy interacts with the radiation fields on the way from the source to Earth. The most important interaction is the photodisintegration. In the first part, we implemented analytical, numerical and Monte Carlo simulation solutions for the photodisintegration rate. We show solutions based on parameterizations of the cross-section using Gaussian and Lorenztian functions. We compare our results with previous works. The following study shows that under the assumption of quasi-linear propagation and using several sources distributions of sky, the latitude of the observatory: has influence on the total flux measured by an observatory; imposes a limitation on the capability of measuring an anisotropic sky and has a negligible efect on the Xmax measurement. In the thirdy study, an upper limit on the integral flux of GeV-TeV gamma-rays is used to extract the upper limit on the total UHECR luminosity of individual sources. The correlation between upper limit on the integral GeV-TeV gamma-rays flux and upper limit on the UHECR luminosity is established through the cascading process that takes place during propagation of the cosmic-rays in the background radiation fields.
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Bustamante, Ramírez Mauricio [Verfasser], Walter [Gutachter] Winter, Karl [Gutachter] Mannheim, and Raimund [Gutachter] Ströhmer. "Ultra-high-energy neutrinos and cosmic rays from gamma-ray bursts: exploring and updating the connection / Mauricio Bustamante. Gutachter: Walter Winter ; Karl Mannheim ; Raimund Ströhmer." Würzburg : Universität Würzburg, 2015. http://d-nb.info/111188692X/34.
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El, Aisati Chaimae. "Gamma-ray and Neutrino Lines from Dark Matter: multi-messenger and dedicated smoking-gun searches." Doctoral thesis, Universite Libre de Bruxelles, 2018. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/266180.
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Identifying what makes up the Dark Matter is a long-standing problem to which the abundance of gravitational and cosmological evidence fails to answer. Indirect detection techniques have the aim to unveil the nature of Dark Matter by catching and identifying the products of potential decays and/or annihilations. The work exposed in this thesis is in line with this strategy and has for common thread the quest for line(-like) features in the extraterrestrial fluxes of gamma-rays and neutrinos. The motivation behind this specific interest is that, due to the absence of astrophysical counterparts beyond the GeV scale, these features constitute the ultimate probes (also called “smoking guns”) of the existence of Dark Matter.The thesis is organized in three Parts, the first of which is an introduction to the different facets of the Dark Matter conundrum and why it is not a trivial issue. The works involving gamma-ray line considerations are gathered in Part II, and those exclusively focusing on neutrino lines in Part III.Part II focuses on the effective field theory of Dark Matter decay, first in the context of millicharged particles decaying to gamma-ray lines, and then in the context of (neutral and millicharged) Dark Matter decays involving the simultaneous emission of gamma-ray and neutrino lines. In both cases, the simultaneous emission of cosmic rays is unavoidable and the decays are constrained in a multi-messenger fashion. The complementarity of the results obtained is used to derive model-independent constraints on the Dark Matter lifetime, and shows the possibility to exclude or distinguishsome specific scenarios on the basis of an explicit experimental conjecture.After an introduction to the neutrino detection principles and to the operation of the IceCube detector, Part III focuses on two careful searches for spectral features in the neutrino spectrum. The main goal behind these analyses, conducted in two different regions of the energy spectrum but using the same likelihood ratio procedure, is to popularize dedicated energy distribution studies by showing their ability to reach sensitivity levels comparable to—sometimes even going beyond—those obtained with angular distribution studies or even in the context of gamma-ray line searches.Option Physique du Doctorat en Sciences
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Díaz, Trigo María. "Collecting heat during the day, observing the sky at night the use of a heliostat field near Almería to search for cosmic gamma rays /." [S.l. : s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964426986.
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Heinze, Jonas. "Ultra-high-energy cosmic-ray nuclei and neutrinos in models of gamma-ray bursts and extragalactic propagation." Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/21386.
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Utrahochenergetische kosmische Strahlung (ultra-high-energy cosmic rays -- UHECR) besteht aus ionisierten Atomkernen mit den höchsten Teilchenergien, die je gemessen wurden.
Zwar wurden die Quellen von UHECRs noch nicht eindeutig identifiziert, doch gibt es deutliche Anzeichen, dass sie extragalaktisch sind.
Um die Beobachtungen zu interpretieren, wird ein Modell der Wechselwirkungen mit Photofeldern sowohl in der Quelle als auch während der extragalaktischen Propagation benötigt.
Bei diesen Wechselwirkungen werden sekundäre Neutrinos erzeugt.
Diese Dissertation behandelt Modelle der Quellen von UHECRs und die damit verbundene Produktion von Neutrinos sowohl in den Quellen als auch während der Propagation.
Dafür wurde ein neuer Code, PriNCe, für die Propagation von UHECRs entwickelt. Dieser Code wird in einem umfangreichen Parameterscan für ein generisches Quellenmodell angewendet, welches mit dem Spektralindex, der maximalen Rigidität, der kosmologischen Quellenverteilung und der chemischen Komposition als freie Parameter definiert ist. Dabei wird der Einfluss von verschiedenen Photodisintegrations- und Luftschauermodellen auf die erwarteten Eigenschaften der Quellen demonstriert.
Der Fluss kosmogenischer Neutrinos, der sich daraus robust vorhersagen lässt, liegt außerhalb der Reichweite aller derzeit geplanten Neutrinodetektoren.
GRBs als mögliche Quellen von UHECRs werden im Multi-Collision Internal-Shock Modell simuliert, welches die Abhängigkeit der Strahlungsprozesse von den verschiedenen Dissipationsradien im Plasmajet berücksichtigt.
Für dieses Modell wird der Effekt demonstriert, den verschiedene Annahmen über die anfängliche Verteilung des Plasmajets und das hydrodynamische Modell auf die resultierende UHECR- und Neutrinosstrahlung haben.
Für den Gammastrahlenblitz GRB170817A, welcher zusammen mit einem Gravitationswellensignal beobachtet wurde, werden Vorhersagen für den Neutrinofluss und ihre Abhängigkeit vom Beobachtungswinkel gemacht.Ultra-high-energy cosmic rays (UHECRs) are the most energetic particles observed in the Universe. While the astrophysical sources of UHECRs have not yet been uniquely identified, there are strong indications for an extragalactic origin. The interpretation of the observations requires both simulations of UHECR acceleration and energy losses inside the source environment as well as interactions during extragalactic propagation. Due to their extreme energies, UHECR will interact with photons in these environments, producing a flux of secondary neutrinos. This dissertation deals with models of UHECR sources and the accompanying neutrino production in the source environment and during extragalactic propagation. We have developed a new, computationally efficient code, PriNCe, for the extragalactic propagation of UHECR nuclei. The PriNCe code is applied for an extensive parameter scan of a generic source model that is described by the spectral index, the maximal rigidity, the cosmological source evolution and the injected mass composition. In this scan, we demonstrate the impact of different disintegration and air-shower models on the inferred source properties. A prediction for the expected flux of cosmogenic neutrinos is also derived. GRBs are discussed as specific UHECR source candidates in the multi-collision internal-shock model. This model takes the radiation from different radii in the GRB outflow into account. We demonstrate how different assumptions about the initial setup of the jet and the hydrodynamic collision model impact the production of UHECRs and neutrinos. Motivated by the multi-messenger observation of GRB170817A, we discuss the expected neutrino production from this GRB and its dependence on the observation angle. We show that the neutrino flux for this event is at least four orders of magnitude below the detection limit for different geometries of the plasma jet.
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Raab, Christoph. "Searches for Neutrino Emission from Blazar Flares with IceCube." Doctoral thesis, Universite Libre de Bruxelles, 2021. https://dipot.ulb.ac.be/dspace/bitstream/2013/325215/3/toc.pdf.
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Cosmic rays reach Earth from beyond the Milky Way and with energies up to 10^20 eV.The responsible accelerators have to date not been discovered. However, multi-messenger astronomy can shed light on the question, based on the principle that protons and nuclei accelerated in dense and energetic environments would also produce gamma rays and neutrinos. Such environments may be found in "blazars", which are therefore cosmic ray accelerator candidates. Their gamma-ray emission has been observed to increase, sometimes by orders of magnitude, during "flares" as observed in light curves taken by the Large Angle Telescope on the Fermi satellite. When the latter was launched in 2008, the IceCube Neutrino Observatory had also started taking data, detecting the Cherenkov light from high-energy neutrino interactions in the glacier ice under the geographic South Pole. These two experiments have enabled multi-messenger searches for neutrinos in time correlation with the gamma-ray emission from blazars. This work builds on this principle and extends it by "stacking" the signal from multiple blazar flares. Thus, their individually undetectable neutrino emission could still be discoverable. One first analysis focused on the blazar TXS 0506+056, whose flare in 2017 coincided with arrival of the neutrino IceCube-170922A. Extending into a lower energy range than the alert, the search found no additional excess neutrinos associated with the flare. A second analysis used 179 bright and variable blazars. They were divided in two specific blazar classes and weighted relatively to each other, with two weighting schemes motivated physically using the observed gamma-ray luminosity and a third, generic weighting to cover unconsidered scenarios. No significant neutrino excess was found in the unblinded likelihood fits for any of the source catalogues and weighting schemes. Their combined trial-corrected p-value was p=(79.1 +/- 0.3)%. The limits derived from this analysis are also discussed and its relation with other searches considered. Since that was the first "blazar flare stacking", this work also proposes further improvements to the analysis which will help advance the search for cosmic ray accelerators.Les rayons cosmiques proviennent d'au-delà de la Voie lactée et atteignent la Terre avec des énergies pouvant aller jusqu'à 10^20 eV. Les objets qui accélèrent ces rayons cosmiques n'ont toujours pas été découverts. Toutefois, l'astronomie multimessager peut apporter un élément de réponse à cette question, en supposant que les protons et les noyaux accélérés dans des environnements denses et énergétiques pourraient également produire des rayons gamma et des neutrinos. Les "blazars" sont de possibles candidats pour les accélérateurs de rayons cosmiques. Une augmentation de leurs émissions de rayons gamma, parfois de plusieurs ordres de grandeur, a été observée lors de phénomènes qu'on appelle "éruption", comme le montrent les courbes de lumière prises par le télescope spatial Fermi-LAT. Lorsque ce dernier a été lancé en 2008, l'observatoire de neutrinos IceCube avait également commencé à prendre des données, détectant la lumière Tcherenkov provenant d'interactions de neutrinos à haute énergie dans la glace qui se trouve sous le Pôle Sud géographique. Ces deux expériences ont permis de mener à bien des recherches multi-messagers de neutrinos en corrélation temporelle avec l'émission de rayons gamma des blazars. Ce principe est le point de départ de cette thèse, qui va plus loin en employant la méthode du "stacking", qui consiste à combiner les signaux provenant de plusieurs éruptions de blazars. Ainsi, leurs émissions individuelles de neutrinos, habituellement indétectables, pourraient être découvertes après combinaison. Une première analyse s'est concentrée sur le blazar TXS 0506+056, dont l'éruption en 2017 a coïncidée avec l'arrivée de l'évènement IceCube-170922A. En considérant une gamme d'énergie inférieure à celle de l'alerte 170922-A, pas d’autres neutrino excédentaire n’a été associé à l'éruption. Une deuxième analyse est basée sur 179 blazars lumineux et variables. Ces blazars ont été répartis en deux classes spécifiques, et chacun d'entre eux a reçu un poids relatif. Trois schémas de pondération ont été considérés :les deux premiers étant motivés par des observations, le troisième étant plus générique. Aucun excès significatif de neutrinos n'a été observé après avoir effectué des ajustements par maximum de vraisemblance sur les données non masquées, pour les différents catalogues de sources et schémas de pondération. Leur valeur-p combinée est de p=(79.1 +/- 0.3)%. Les limites dérivées de cette analyse sont discutées ainsi que leur rapport avec les résultats d'autres recherches. Puisqu'il s'agit du premier stacking d'éruptions de blazars, nous suggérons également des améliorations à apporter à l'analyse afin de permettre la poursuivre de la recherche d'accélérateurs de rayons cosmiques.
Kosmische straling afkomstig van buiten de Melkweg bereikt de Aarde met energieën tot wel 10^20 eV. De astrofysische bronnen waarin deze deeltjes worden versneld zijn tot op heden nog niet ontdekt. De multi-boodschapperastronomie kan een nieuw licht werpen op de oorsprong van kosmische straling, aangezien protonen en atoomkernen die worden versneld in een dichte en energetische omgeving ook gammastralen en neutrino’s produceren. „Blazars” zijn mogelijke kandidaat-versnellers. Observaties van blazars, gemaakt met de ruimtetelescoop Fermi-LAT ,tonen aan dat hun gammastraling tijdens zogenaamde „flakkers” toeneemt. Rond de tijd dat deze werd gelanceerd, begon het IceCube Neutrino Observatorium ook gegevens te verzamelen. Deze laatste detecteert hoog-energetische neutrino’s aan de hand van het Cherenkovlicht dat geproduceerd wordt tijdens hun interacties met de ijskap bij de geografische zuidpool. Deze twee experimenten hebben het mogelijk gemaakt om een multibooschapperzoektocht te verrichten naar neutrino’s van blazars die een tijdscorrelatie hebben met diens flakkers van gammastraling. Dit is het uitgangspunt van dit proefschrift, waarbij er ook een zogenaamde „stapelmethode” wordt toegepast. Op deze manier kan de neutrino-emissie van indivuele blazarflakkers, die afzonderlijk te zwak is om te detecteren, gecombineerd worden en mogelijks toch worden ontdekt. Een eerste analyse legt de focus op de blazar TXS 0506+056, waarvan een flakker in 2017 samenviel met de aankomst van het neutrino IceCube 170922-A. In een relatief lager energiebereik wordt er geen surplus aan neutrino’s gevonden gecorreleerd met de flakker. In een tweede analyse maken we gebruik van de stapelmethode om neutrino’s te zoeken afkomstig van 179 heldere en variabale blazars. Deze worden onderverdeeld in twee specifieke klassen en krijgen elks een zeker gewicht in de stapelanalyse. Hiervoor worden twee wegingsschema’s gebruikt die gemotiveerd zijn door de geobserveerde gammastraling, alsook een derde generieke weging. Ook hierwordt er geen significant neutrinosignaal geobserveerd. De gecombineerde p waarde is p=(79.1 +/- 0.3)%. Hieruit worden limieten afgeleid, en worden de verbanden met andere zoekacties besproken. Aangezien dit werk de eerste analyse omvat naar neutrino’s afkomstig van blazarflakkers gebruik makende van een stapelmethode, worden er in dit werk ook verdere verbeteringen van de analyse voorgesteld. Deze zullen als een startpunt dienen voor toekomstige zoektochten naar de nog onbekende bronnen van kosmische straling.
Doctorat en Sciences
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Krayzel, Fabien. "Etude de phénomènes non-thermiques dans les amas d'étoiles jeunes : modélisation et analyse des données de H.E.S.S." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENY079.
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Voilà plus d'un siècle que Victor Hess a montré l'origine cosmique de ce mystérieux rayonnement ionisant, et pourtant ce dernier n'a pas fini de livrer tous ces secrets. En deçà d'une énergie de l'ordre du PeV, les vestiges de supernovae sont les candidats les plus sérieux pour rendre compte de l'accélération de ces particules cosmiques. Si toutefois cette hypothèse demeure toujours d'actualité, alors qu'auparavant on le considérait comme un événement isolé dans la Galaxie, on constate plutôt aujourd'hui que ces explosions d'étoiles massives surviennent majoritairement au sein de grandes structures galactiques nommées superbulles. Ces objets sont formés par la combinaison des forts vents stellaires issus des étoiles massives ainsi que de plusieurs supernovae, tout ceci regroupé dans un espace de quelques dizaines ou centaines de parsecs.On peut dès lors se poser la question suivante : est-il possible que des amas d'étoiles jeunes, n'ayant pas encore connu d'épisode de supernova, puissent être des accélérateurs cosmiques.Pour ce type d'investigation, l'astronomie gamma est aux premières loges puisque contrairement au rayonnement cosmique chargé, ce type de messager céleste n'est pas dévié dans son voyage depuis la source jusqu'à nous.L'objet de ce travail est ainsi d'évaluer la possibilité pour ces amas d'étoiles jeunes, de recycler une partie de l'énergie mécanique transférée au milieu interstellaire dans l'accélération de particules et partant, dans l'émission d'un rayonnement non-thermique. Cette étude propose, à partir d'un spectre d'injection pour des particules chargées (proton et/ou électrons), de modéliser l'émission non-thermique attendue considérant les pertes que celles-ci subissent. Un catalogue d'amas potentiellement prometteurs est dressé ainsi qu'un classement de ceux-ci au regard du flux de gamma attendu. Une analyse des données des télescopes H.E.S.S. est conduite pour un certain nombre d'amas sélectionnés. Ce réseau de télescopes Cherenkov situé en Namibie est le plus performant dans sa catégorie. Il est dédié à l'observation des rayons gamma de très haute énergie.Une analyse des données du Fermi-LAT ont également été effectuées. Il s'agit cette fois d'un satellite dédié à la partie des hautes énergies du rayonnement gamma.Enfin, on contraint les paramètres de notre modèle grâce aux résultats issus de ces analyses.L'expérience H.E.S.S., qui a fonctionné à 4 télescopes dès 2003, est depuis 2012 au tout début de sa deuxième phase consistant en l'ajout d'un cinquième télescope de plus grand diamètre. On montre ici, grâce à des simulations de gerbes, la nécessité pour ce télescope de disposer d'un système de focus permettant l'ajustement de la distance caméra-miroirs conduisant à de meilleures performances (taux de déclenchement, résolution angulaire)More than one century ago, Victor Hess discovered the cosmical origin of the mysterious ionizing radiation. Yet, nowadays it still has a lot of secrets for us. Roughly below the PeV energy, the best candidates already proposed in 1934 were the supernovae remnants (SNR). These candidates still remain ; in the past we considered isolated SNRs, while today we rather think about SNRs inside big structures as superbubbles. These objects are formed by powerful stellar winds from massive stars combined with several SNRs gathered in a space of some decades or hundreds of parsecs. Observations show that the majority of the SNRs occurs in such regions. The point for us is to know if star clusters or associations of massive stars, not hosting any SNR, could also accelerate particles to very high energies and consequently emit gamma-rays.The gamma-ray astronomy is relevant in order to solve this type of riddle because the Very High Energy photons do not suffer of any deviation due to the Galactic magnetic field. It means that we can get informations from the source itself by detecting the gamma-ray radiation.In our study we assume that a part of the mechanical energy transferred to the interstellar medium can be used to accelerate charged particles, which will emit non-thermal radiations.First we assume a given injection spectrum (for electrons and/or protons), then we model the non-thermal emission expected considering particles losses.We deliver a catalogue of promising clusters and we rank them according to the expected strength of the gamma-ray flux.We conducted the analysis of H.E.S.S. data collected toward some selected clusters. The H.E.S.S. experiment is situated in Namibia and is the most efficient array of Cherenkov telescopes. We also used the Fermi-LAT public data. Fermi is a space-based telescope for High Energy gamma ray.Then we constrain our model with the obtained analysis results.The H.E.S.S. experiment had initially 4 telescopes in operation since 2003. In 2012, the second phase of the experiment started when a fifth larger one was added. We show here that it is relevant for this telescope to use a focus system in order to move the camera and change the distance camera-mirrors. The simulations show that the focus system leads to better performances (trigger rate, angular resolution)
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Bonnivard, Vincent. "Détection indirecte de matière noire : des galaxies naines sphéroïdes en photons gamma à la recherche d'anti-hélium avec l'expérience AMS-02." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAY022/document.
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De nombreuses observations astrophysiques indiquent l'existence de grandes quantités de masse manquante dans l'Univers, et ce de l'échelle galactique à l'échelle cosmologique. Découvrir la nature de cette masse invisible constitue le problème de la matière noire, qui apparaît comme l'un des enjeux majeurs de la physique moderne. Cette thèse s'inscrit dans le contexte de la détection indirecte de matière noire. Cette dernière serait composée de nouvelles particules élémentaires, dont les produits d'annihilation pourraient être observés dans le rayonnement cosmique. Nous étudions dans ce travail deux des canaux de recherche les plus prometteurs : les photons gamma et les anti-noyaux.Les objets astrophysiques permettant de placer les meilleures contraintes actuelles en rayons gamma sont les galaxies naines sphéroïdes (dSphs) de la Voie Lactée. La première partie de notre travail a été consacrée à contraindre les facteurs J d'annihilation de ces objets, qui quantifient l'amplitude des flux gamma attendus. Nous avons pour cela mis au point une configuration optimisée d'analyse de Jeans, pour reconstruire les profils de densité de matière noire et leurs incertitudes à l'aide des données cinématiques stellaires. Notre configuration a été obtenue à l'aide de tests systématiques sur de très nombreuses dSphs simulées, et nous l'avons appliquée à vingt-trois dSphs de la Voie Lactée. La seconde partie de notre travail a consisté à mener une recherche de noyaux d'anti-hélium dans les données collectées par l'expérience AMS-02 sur la Station Spatiale Internationale. Nous avons pour cela mis au point une classification par arbres de décision boostés, et notre analyse préliminaire a permis d'obtenir les meilleures contraintes actuelles sur les rapports anti-hélium sur héliumMany astrophysical observations suggest the existence of large amounts of missing mass in the Universe, from the galactic to the cosmological scale. Discovering the nature of this invisible mass forms the dark matter problem, which appears as one of the major challenges of modern physics. This thesis is established in the context of indirect detection of dark matter. The latter could consist of new elementary particles, whose annihilation products may be observed in cosmic rays. We study in this work two of the most promising research channels!: gamma-rays and anti-nuclei.The best constraints on dark matter properties from gamma-ray observations come from the dwarf spheroidal galaxies (dSphs) of the Milky Way. The first part of our work was devoted to computing the annihilation J-factors of these objects, which quantify the magnitude of the expected gamma-ray flux. We have developed an optimized Jeans analysis setup in order to reconstruct the dark matter density profiles of these objects and their associated uncertainties, using stellar kinematic data. Our optimized setup was obtained using systematic tests on numerous simulated dSphs, and we applied it to twenty-three dSphs of the Milky Way. The second part of our work was dedicated to the search for anti-helium nuclei in the cosmic ray data collected by the AMS-02 experiment on the International Space Station. We have developed a classification method using boosted decision trees, and our preliminary analysis has led to the best constraints to date on the anti-helium to helium ratio
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Trichard, Cyril. "Etude du rayonnement gamma de vestiges de supernova en interaction avec des nuages moléculaires et optimisation de l'analyse des données de H.E.S.S." Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAY070/document.
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L'expérience H.E.S.S. est un réseau de télescope Tcherenkov, situé en Namibie, qui observe le rayonnement de sources astrophysiques de rayons gamma de très haute énergie. Depuis sa mise en service il y a plus de dix ans, H.E.S.S. a permis d'améliorer considérablement notre vision de l'univers à ces énergies. Depuis 2012, le démarrage de la deuxième phase de l'expérience avec la mise en service d'un cinquième télescope permet de baisser le seuil en énergie de l'expérience.L'optimisation d'une analyse multivariée au sein de l'expérience H.E.S.S. est présentée dans cette thèse. L'analyse Xeff a été amélioré en prenant en compte les conditions d'observations, et en introduisant de nouvelles variables dans l'estimateur. Un gain de sensibilité de l'analyse par rapport aux analyses standards est observé. Cette méthode a été ensuite utilisée pour diverses analyses de sources de rayons gamma.La prise en compte des effets de la focalisation de l'analyse de données de H.E.S.S. II est détaillée. L'ajustement de la distance entre la caméra et les miroir du cinquième télescope permet d'améliorer l'image dans le plan focal. L'amélioration de la reconstruction et le gain en sensibilité qui en découle est présenté.L'étude du rayonnement gamma de quatre candidats d'associations de vestiges de supernova et de nuages moléculaires est présentée : G349.7+0.2, W51, la nébuleuse de la Tornade, et HESS J1745-303. Une interprétation de ce rayonnement utilisant également les données de Fermi-LAT permet d'estimer l'origine dominante des mécanismes d'émission et d'appréhender l'efficacité d'accélération de particules par ces systèmes.Les travaux présentés dans cette thèse ont fait l'objet de deux notes internes à la collaboration H.E.S.S., de multiples présentations dans des conférences internationales et de publications scientifiquesThe H.E.S.S. experiment is an array of Cherenkov telescopes, located in Namibia, observing the very high energy gamma rays from astrophysical sources. H.E.S.S. greatly increased our understanding of the very high energy non thermal universe. Since 2012, a fifth telescope was installed at the center of the array. This improvement increase the energy range and the sensitivity of the detector.The optimization of a multivariate analysis method, within the H.E.S.S. framework, is presented in this thesis. The Xeff analysis is improved by taking into account the observation conditions and by increasing the number of discriminating variables. The sensitivity of this analysis compared to standard analyses is demonstrated. Xeff is then used to analyze several sources of gamma rays.The effects of the focus impacting the H.E.S.S. II data are described. They are taken into account in the analysis and an optimization of the distance between the mirrors and the camera is presented.The study of the gamma emission from four candidates of molecular clouds and supernova remnant associations is presented. The H.E.S.S. data from G349.7+0.2, W51, the Tornado nebula and HESS J1745-303 is performed. The interpretation of their emission, using also Fermi-LAT data, leads to the estimation of the particles acceleration efficiency in these objects.The work described in this thesis led to the production of two internal notes in the H.E.S.S. collaboration, to several presentations in international conferences, and scientific publications
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Porelli, Andrea. "TAIGA-HiSCORE: a new wide-angle air Cherenkov detector for multi-TeV gamma-astronomy and cosmic ray physics." Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/21610.
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Der TAIGA Detektor (“Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy”) testet eine neue Nachweismethode der erdgebundenen Cherenkov Gamma Astronomie fuer 10TeV bis einige PeV, und fuer kosmische Strahlung oberhalb 100TeV: die Kombination abbildender und nicht-abbildender Cherenkov Detektoren in einem hybriden System.
Im Fokus der Arbeit steht TAIGA-HiSCORE - ein Cherenkov Detektorfeld mit grosser Apertur zur Messung der Zeitstruktur der Cherenkovlichtfront in atmosphaerischen Luftschauern (EAS). Die Praezisonsvermessung der Schauerrichtung basiert auf
(1) sub-nsec Zeitsynchronisation aller Detektoren, und
(2) einer neuentwickelten Zeitkalibrationsmethode.
Die Genauigkeit wird bestimmt mit experimentellen und simulierten EAS-Daten, spezieller LED-Kalibration und dem LIDAR Laserstrahl aus der International Space Station (ISS).
Mit den HiSCORE9 Daten (2013-2014) wird die sub-nsec Zeitsynchronisation durch das White Rabbit Zeitsystem unter realen Bedingungen nachgewiesen. Eine neue, auch fuer grosse Cherenkov-Detektorfelder praktikable Zeitoffset-Kalibration aller Detektoren wurde entwickelt, und fuer HiSCORE28 (2015-2018) angewandt. Diese hybride Kalibration basiert auf EAS-Ereignissen und direkter LED-Kalibration fuer lediglich eine begrenzte Zahl von Detektoren.
Die Genauigkeit der Luftschauer-Richtungsrekonstruktion wird ueber die “Schachbrett-Methode” MC-unabhaengig bestimmt zu 0.4° an der Energieschwelle (50TeV) und <= 0.2° fuer > 100TeV.
Eine wichtige Zufallsentdeckung war mit HiSCORE28 moeglich: der Laser des ISS-CATS-Lidars wurde in richtungsrekonstruierten Daten von HiSCORE28 nachgewiesen. Mit den “ISS Ereignissen” gelang es, sowohl die Rekonstruktionsgenauigkeit von HiSCORE, als auch das “absolute pointing” zu messen (<=0.1°) - besonders wichtig, da eine starke Gamma-Quelle im Datensatz bisher nicht nachgewiesen wurde. Im Schlussteil der Arbeit wird ein Methode zur Punktquellensuche im gesamten Gesichtsfeld von TAIGA-HiSCORE vorgestellt.The TAIGA (Tunka Advanced Instrument for cosmic ray physics and Gamma Astronomy) detector is a new ground-based Cherenkov detection technology for gamma-astronomy from 10TeV up to several PeV, and cosmic rays (CR) above 100TeV. The main topic of this work is TAIGA-HiSCORE, the wide-aperture air Cherenkov timing array. The focus is on precision extensive air shower (EAS) arrival direction reconstruction, achieved by (1) sub-nsec time-synchronization between the array stations, and (2) a newly developed array time calibration procedure. The performance is verified using simulated and experimental data from EAS, dedicated LED calibration, and a LIDAR laser beam from the International Space Station (ISS). The analysis of the HiSCORE 9 data (2013-14), collected with a data acquisition system (DAQ) based on the White Rabbit (WR) timing system, allows to verify the sub-nsec time synchronization between the array stations. The analysis of HiSCORE 28 data (2015-2018) addresses the problem of achieving an easy-to-perform time calibration for large area ground-based Cherenkov array. A new "hybrid" calibration method is developed, which makes use of EAS data, and requires direct LED calibration of only a few array stations. The "chessboard" method is applied on the reconstructed data to obtain a MC-independent estimation of the detector angular resolution, found to be 0.4° at threshold (~50TeV) and <= 0.2° above 100TeV. A serendipitous discovery was made in this work: a signal from the CATS-LIDAR on-board the ISS was found in the HiSCORE 28 data. These "ISS-events" are used to verify the detector performance, in particular the absolute angular pointing (<= 0.1°), particularly important since a strong gamma point source has not yet been detected by the TAIGA-HiSCORE. The final part of the work presents a first preliminary approach to a wide aperture point source analysis, developed for the TAIGA-HiSCORE in stand-alone operation.
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Biehl, Daniel. "Nuclear Cascades and Neutrino Production in the Sources of Ultra-High Energy Cosmic Ray Nuclei." Doctoral thesis, Humboldt-Universität zu Berlin, 2019. http://dx.doi.org/10.18452/20448.
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Der Ursprung ultra-hochenergetischer kosmischer Strahlung (UHECRs) ist eine der wichtigsten offenen Fragen der Astrophysik. Gammastrahlenblitze (GRBs) galten als potentielle Quellen, da sie zu den energetischsten Ereignissen im Universum zählen. Konventionelle Szenarien sind jedoch durch Neutrinodaten stark eingeschränkt. Außerdem weisen Messungen der chemischen Zusammensetzung kosmischer Strahlen auf schwere Kerne hin, welche in zu dichten Strahlungsfeldern disintegrieren würden. Um dieses Dilemma zu umgehen deuten neue Studien auf versteckte Beschleuniger hin, welche schwer zu detektieren sind. In dieser Dissertation präsentieren wir neue Ansätze um nukleare Prozesse in astrophysikalischen Quellen effizient und selbstkonsistent zu berechnen. Wir quantifizieren diese Wechselwirkungen anhand der nuklearen Kaskade, welche die Disintegration schwerer Kerne in leichtere Fragmente beschreibt. Auch in umfassenden Modellen, wie sie in dieser Arbeit entwickelt werden, sind GRBs durch Neutrinodaten unter Druck. Dennoch zeigen wir, dass eine Population von GRBs niedriger Luminosität konsistent mit derzeitigen Messungen ist und zugleich auch das Spektrum und die Zusammensetzung kosmischer Strahlung über den Knöchel hinweg sowie Neutrinodaten beschreiben kann. Aus unserer Prozedur können wir zusätzlich weitere Quelleneigenschaften wie die baryonische Ladung oder die Ereignisrate bestimmen. Wir zeigen weiter, dass auch von schwarzen Löchern zerrissene Sterne mögliche Kandidaten eines gemeinsamen Ursprungs der gemessenen kosmischen Strahlung und PeV-Neutrinos sind. Sie können jedoch durch kosmogenische Neutrinos von LLGRBs abgegrenzt werden. Schließlich wenden wir unser Modell auf das Gravitationswellenereignis GW170817 an. Wir zeigen für verschiedene Jet-Szenarien, dass der erwartete Neutrinofluss weit unter der Sensitivität derzeitiger Instrumente liegt. Dennoch könnten verschmelzende Neutronensterne die kosmische Strahlung unterhalb des Knöchels erklären.The origin of Ultra-High Energy Cosmic Rays (UHECRs) is still one of the most important open questions in astrophysics. Gamma-Ray Bursts (GRBs) were considered as potential sources as they are among the most energetic events known in the Universe. However, conventional GRB scenarios are strongly constrained by astrophysical neutrino data. In addition, cosmic ray composition measurements indicate the presence of heavy nuclei, which would disintegrate if the radiation fields in the source were too dense. In order to circumvent this dilemma, recent studies point towards hidden accelerators, which are intrinsically hard to detect. In this dissertation, we present novel approaches to efficiently and self-consistently calculate the nuclear processes in astrophysical sources. We quantify these interactions by means of the nuclear cascade, which describes the subsequent disintegration of heavy nuclei into lighter fragments. Even in sophisticated source-propagation models, as the ones developed in this thesis, conventional GRBs are in tension with neutrino data. However, we demonstrate that a population of low-luminosity GRBs is not only consistent with current constraints, but can even describe the UHECR spectrum and composition across the ankle as well as neutrino data simultaneously. From our fitting procedure we can further constrain certain source properties, such as the baryonic loading and the event rate. Furthermore, we show that stars disrupted by black holes are viable candidates for a simultaneous description of cosmic ray and PeV neutrino data too. However, they can be discriminated from LLGRBs by cosmogenic neutrinos. Finally, we apply our model to GW170817. We show for different jet scenarios that the expected neutrino flux is orders of magnitude below the sensitivity of current instruments. Nevertheless, binary neutron star mergers could in principle support cosmic rays below the ankle.
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Joubaud, Théo. "Etude de la superbulle d'Orion-Eridanus : gaz, champs magnétiques et rayons cosmiques." Thesis, Université de Paris (2019-....), 2019. http://www.theses.fr/2019UNIP7077.
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La plupart des supernovae dans notre Galaxie explosent dans des amas d’étoiles massives. Avec les vents et les rayonnements intenses des étoiles les plus massives elles forment des bulles chaudes en expansion, d’une taille d’une centaine de parsecs, appelées superbulles. Ces régions de la Galaxie sont des laboratoires de choix pour étudier la rétroaction stellaire sur le milieu interstellaire. Le gaz et les champs magnétiques initialement présents sont balayés. Une cavité se forme, remplie d’un plasma turbulent et traversée par de nombreuses ondes de chocs. Ce type d’environnement peut fortement perturber la propagation des rayons cosmiques. La contribution des superbulles à la production des rayons cosmiques Galactiques reste cependant inconnue. En 2011, le Fermi Large Area Télescope (LAT) a identifié en rayonsγ un coco de jeunes rayons cosmiques, accélérés dans la superbulle de Cygnus X. Cette première découverte a motivé la recherche et l’analyse d’autres amas d’étoiles massives. La proximité de la superbulle d’Orion-Eridanus en fait un bon candidat. Nous avons étudié la partie de la superbulle la plus proche et visible loin du plan Galactique, dans la constellation de l’Éridan. Les observations à différentes longueurs d’ondes du spectre électromagnétique ont permis d’étudier la structure du gaz et des champs magnétiques de la superbulle. À partir des informations en vitesse des raies d’émission du H I et du CO, nous avons identifié différentes coquilles de gaz associées à la superbulle. Elles indiquent une vitesse d’expansion globale de 20 km s−1. Des cartes 3D du rougissement des poussières ont permis de confirmer cette séparation en coquilles et de contraindre leurs distances au Soleil entre 150 et 250 pc. L’absorption des rayons X a permis de les positionner par rapport au gaz chaud de la superbulle. Ce gaz chaud apparaît hétérogène, avec un mélange sur les lignes de visée de plasmas à 0.3-1.2 MK et 3-9 MK. La composante du champ magnétique dans le plan du ciel peut être tracée par l’émission polarisée des poussières observée par Planck. Les données montrent que le champ dans la coquille externe a été réorganisé et comprimé par l’expansion de la superbulle. En utilisant la méthode de Davis-Chandrasekhar-Fermi et en veillant à la cohérence avec la dynamique du gaz au travers du choc externe, nous avons obtenu des intensités du champ magnétique dans la coquille entre 3 et 15 µG. Nous avons mesuré le flux de rayons cosmiques dans les coquilles de la superbulle avec 10 ans de données du télescope Fermi-LAT entre 0.25 et 63 GeV. À ces énergies, le rayonnement γ trace principalement l’interaction des rayons cosmiques avec le gaz interstellaire. Nous avons modélisé les distributions spatiale et spectrale des rayons γ issus des différentes phases de gaz (atomique, moléculaire, sombre et ionisé). Des émissions γ non liées au gaz sont également prises en compte. Notre analyse révèle que les spectres d’émissivité γ dans les coquilles de la superbulle sont compatibles avec le spectre moyen de rayons cosmiques mesuré dans le milieu interstellaire local et dans le Système Solaire. Une telle homogénéité montre que la superbulle n’est pas active en termes de production et de réaccéléra de rayons cosmiques, et nous discutons plusieurs explications possibles. Un nuage diffus, situé en dehors de la bulle et à une altitude de 200-250 pc sous le plan Galactique, présente une émissivité γ 34% plus faible mais sans modification spectrale. Cette perte de rayons cosmiques est significative et nous avançons l’hypothèse qu’elle est liée à l’orientation des lignes de champ magnétique du nuage qui pointent vers le halo Galactique. Enfin, en compilant nos mesures d’émissivité avec celles d’analyses précédentes, nous avons étudié la variation locale du flux de rayons cosmiques selon l’altitude au-dessus du plan Galactique, et nous comparons ces mesures aux prédictions des modèlesMost of the supernovae in our Galaxy explode in massive stellar clusters. Together with the winds and intense radiations from the most massive stars, they create 100-pc-scale, hot expanding bubbles, called superbubbles. Such sites are prime targets to study stellar feedback on the interstellar medium. Theys sweep up gas and magnetic fields. They create cavities filled with turbulent plasmas and shock waves. This type of environment can impact cosmic-ray propagation. The superbubble contribution to the production of Galactic cosmic rays is still unknown. In 2011, the γ-ray Fermi Large Area Telescope (LAT) detected a cocoon of freshly accelerated cosmic rays in the Cygnus X superbubble. This discovery called for investigations of other massive stellar clusters. The proximity of the Orion-Eridanus superbubble makes it a good candidate. We have studied the closer, Eridanus, side of the superbubble, seen far from the Galactic plane. We have used information across the electromagnetic spectrum to study the superbubble gas and magnetic-field structures. From the velocity information of the H I and CO emission lines, we have identified several gas shells related to the superbubble and we have derived a global expansion velocity of 20 km s−1 . Using 3D dust reddening maps, we have confirmed our shell separation and found that their distances range from about 150 pc to 250 pc from the Sun. X-ray absorption constrained their location relative to the hot gas filling the superbubble interior. The latter appears to be heterogeneous, with a mix of 0.3-1.2 MK and 3-9 MK gas along the lines of sight. Lastly, we have studied the plane-of-sky component of the magnetic field with dust polarised emission observed by Planck. The magnetic field along the outer rim and in the approaching wall of the superbubble appears to be shaped and compressed by the ongoing expansion. Using the Davis-Chandrasekhar-Fermi method and requiring consistency with the gas dynamics through the outer shock, we have found plane-of-sky field strengths from 3 to 15 µG along the rim. We have studied the cosmic-ray content of the superbbuble using 10 years of Fermi-LAT data between 0.25 and 63 GeV. In this energy range, the γ radiation mainly traces cosmic-ray interactions with interstellar gas. We have thus modelled the spatial and spectral distributions of the γ rays borne in the different gas phases (atomic, molecular, dark, and ionised). The model includes other non-gaseous components to match the data. We have found that the γ-ray emissivity spectrum of the gas along the outer rim and further inside the bubble is consistent with the average cosmic-ray spectrum measured in the local interstellar medium and in the Solar System. This homogeneity shows that little cosmic-ray production and re-acceleration is taking place inside the superbubble. We discuss the implications for cosmic-ray transport conditions. We also find significant evidence that a diffuse atomic cloud lying outside the superbubble, at an altitude of 200-250 pc below the Galactic plane, is pervaded by a 34% lower cosmic-ray flux, but with the same particle energy distribution as the local one. We tentatively propose that the cosmic-ray loss relates to the orientation of the magnetic field lines threading the cirrus, which point towards the halo. Finally, we have gathered the present emissivity measurements with previous estimates obtained around the Sun to show how the local cosmic-ray flux decreases with Galactic altitude and to compare with model prediction
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Martraire, Diane. "Étude du pouvoir de discrimination des primaires initiant les grandes gerbes atmosphériques avec des réseaux de détecteurs au sol : analyse des rayons cosmiques de ultra haute énergie détectés à l’observatoire Pierre Auger, Estimation des performances pour la detection de gamma de très haute énergie du future observatoire LHAASO." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112276/document.
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Depuis plus d’un siècle, les rayons cosmiques d’ultra-haute énergie (RCUHE), ayant une énergie supérieure à 1018 eV, continuent d’entretenir le mystère : Quelle est leur composition ? D’où viennent-ils ? Comment atteignent-ils de telles énergies ? Ces particules chargées, suffisamment énergétiques pour atteindre la Terre, forment des gerbes de particules secondaires via leurs interactions avec l’atmosphère dont le développement est caractéristique de la nature de la particule primaire. L’observatoire Pierre Auger, avec sa structure hybride et son gigantesque réseau de détecteurs peuvent apporter des réponses. L’étude de la composition des RCUHEs a été étudiée avec le réseau de surface de l’observatoire Pierre Auger. Cette dernière est cruciale à la fois pour comprendre les interactions hadroniques, qui constituent le développement des gerbes, et pour identifier leurs sources. Cela peut également aider à comprendre l’origine de la coupure spectrale aux plus hautes énergies : s’agit-il de la coupure GZK ou à l’extinction des sources. Toutes ces raisons motivent la première partie de la thèse, à savoir la mise en place d’une méthode permettant d’extraire la composante muonique des gerbes atmosphériques et d’en déduire la composition. Les résultats de cette méthode montrent une dépendance de la composition avec la distance à l’axe de la gerbe, qui pourrait aider à améliorer les modèles hadroniques. Dans les conditions actuelles du réseau de surface, l’identification de la composante muonique présente des limites.La seconde partie est consacrée au nouvel observatoire en Chine, LHAASO. Ce projet s’intéresse à l’étude des gammas supérieurs à 30 TeV, qui signeraient l’accélération de proton dans la galaxie, donnant ainsi des informations indirectes sur les rayons cosmiques. D’autre part, l’observatoire vise à étudier les rayons cosmiques entre 10 TeV et 1 EeV, région où le spectre en énergie présente une rupture. Cette région nécessite de pouvoir discriminer les gammas des rayons cosmiques. A ce titre, l’un des détecteurs de LHAASO, le KM2A, a été simulé et son pouvoir de discrimination gamma/hadron évaluéDuring the past century, ultra-high-energy cosmic rays (UHECR), those with an energy larger than 1018 eV, remain as a mystery: What are cosmic rays? Where do they come from? How do they attain their huge energy? When these charged particles strike the earth's atmosphere, they dissipate their energy by generating a shower of secondary particles whose development is significantly different depending on the nature of the primaries. The Pierre Auger observatory, with its hybrid structure and huge size network of ground detectors, can shed some light into these questions.The study of the composition of UHECR was performed with the Pierre Auger apparatus. This is crucial both to understand the hadronic interactions, which govern the evolution of showers, and to identify their sources. It can help to understand the origin of the energy spectrum cut-off: is it the GZK cut-off or the exhaustion of sources? These reasons motivate the first part of this thesis: the development of a method to extract the muonic component of air showers and deduce the implications on the composition of UHECR at the Pierre Auger observatory. The results of this method show a dependence of the composition with the distance to the axis of the shower, which could help to improve the hadronic models. The determination of the muon component is limited by the surface detector setup.The second part is devoted to the new observatory in China, LHAASO. This project focuses on the study of gamma rays with an energy higher than 30 TeV, which probe the acceleration of protons in the galaxy, providing indirect information on cosmic rays. Moreover, the observatory studies cosmic rays between 10 TeV and 1 EeV, one of the regions where the energy spectrum presents a break. This region requires the ability to discriminate gamma rays and cosmic rays. For this reason, one of the detectors of LHAASO, the KM2A, was simulated and its power of discrimination gamma/hadron evaluated
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Norén, Magnus. "Measuring the vertical muon intensity with the ALTO prototype at Linnaeus University." Thesis, Linnéuniversitetet, Institutionen för fysik och elektroteknik (IFE), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-107133.
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ALTO is a project, currently in the research and development phase, with the goal of constructing a Very High Energy (VHE) gamma-ray observatory in the southern hemisphere. It will detect the particle content reaching the ground from the interactions of either VHE gamma rays or cosmic rays in the atmosphere known as extensive air showers. In this thesis, we use an ALTO prototype built at Linneaus University to estimate the vertical muon intensity in Växjö. The atmospheric muons we detect at ground level come from hadronic showers caused by a cosmic ray entering the atmosphere. Such showers are considered background noise in the context of VHE gamma-ray astronomy, and the presence of muons is an important indicator of the nature of the shower, and thus of the primary particle. The measurement is done by isolating events that produce signals in two small scintillation detectors that are part of the ALTO prototype, and are placed almost directly above each other. This gives us a data set that we assume represents muons travelling along a narrow set of trajectories, and by measuring the rate of such events, we estimate the muon intensity. We estimate the corresponding momentum threshold using two different methods; Monte Carlo simulation and calculation of the mean energy loss. The vertical muon intensity found through this method is about 21% higher than commonly accepted values. We discuss some possible explanations for this discrepancy, and conclude that the most likely explanation is that the isolated data set contains a significant number of “false positives”, i.e., events that do not represent a single muon following the desired trajectory.