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Auswahl der wissenschaftlichen Literatur zum Thema „Radioastronomie – Recherche“
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Dissertationen zum Thema "Radioastronomie – Recherche"
Octau, Franck. „Exploration d'un grand relevé à Nançay et diversité de la population de pulsars“. Thesis, Orléans, 2017. http://www.theses.fr/2017ORLE2042/document.
Der volle Inhalt der QuelleSince the discovery of the first pulsar in 1967, we know over 2500 pulsars today. Pulsars offer a broad range of studies: from the study of the properties of interstellar medium and of pulsar magnetospheres up to test of gravity in the strong-field regime and the characterisation of the cosmological Gravitation Waves background. This explains why we keep searching pulsars nowadays. After successful detections of new millisecond pulsars in Fermi Large Area Telescope unassociated sources at Nançay, a blind pulsar survey was initiated in 2012 by G. Desvignes. Conducted at 1.4 GHz with short sampling time and narrow frequency channels, the SPAN512 was designed to find fast and distant pulsars within the Galactic plane. We describe the methods to analyse data in order to find new pulsars, thanks to their spin stability or tto their single pulses. We will also describe the current status of the survey and the discoveries, more especially the pulsar discovered during this thesis, PSR J2055+3829, a 2.08 ms pulsar in a black widow system. It will be the opportunity to present the radio timing analysis of this pulsar and, in the same time, we will describe similar studies conducted on the pulsar J1618-3921, a pulsar in an eccentric orbit. Finally, we present some polarisation studies of pulsars in light of a new model, the Decentred Rotating Vector Model (DRVM). We will show that a highly decentred dipole may explain abrupt variations of polarisation profiles
Desvignes, Grégory. „L'observation des pulsars au Radiotélescope de Nançay : applications à la recherche de nouveaux objets, à l'étude des systèmes binaires relativistes et à la détection d'un fond d'ondes gravitationnelles“. Phd thesis, Université d'Orléans, 2009. http://tel.archives-ouvertes.fr/tel-00496806.
Der volle Inhalt der QuelleDespois, Didier. „Etude du gaz moléculaire tracé par le monoxyde de carbone ¹²CO et ¹³CO dans la galaxie et l'environnement d'étoiles OeBe à l'aide du mini-radiotélescope POMI : recherche de HCN dans les comètes“. Bordeaux 1, 1987. http://www.theses.fr/1987BOR10599.
Der volle Inhalt der QuelleZhang, Xiao. „Restoring dynamic spectra corrupted by radio frequency interference : Application to pulsar observation by SKA-pathfinder low-frequency NenuFAR“. Electronic Thesis or Diss., Orléans, 2024. http://www.theses.fr/2024ORLE1027.
Der volle Inhalt der QuellePulsars are rapidly rotating neutron stars that emit electromagnetic radiation signals received as periodic pulses, thereby acting as cosmic lighthouses. The excellent stability of these periodic signals makes them invaluable tools for assessing the theory of general relativity and for detecting low frequency gravitational waves. However, their observation by radio telescopes can be made difficult by radio frequency interference (RFI) of various origins. These interferences can alter the pulsar signals, which may significantly complicate the detection and precise extraction of their signatures. This thesis aims to propose deep learning techniques to mitigate the impact of RFI in pulsar observations. In particular, this thesis illustrates the interest of these methods in the case of observations carried out by NenuFAR, a pathfinder for the low-frequency segment of the upcoming Square Kilometre Array (SKA).The first part of this thesis begins presenting the astrophysical background of pulsars, emphasizing their importance and role in contemporary astronomy. It then introduces the NenuFAR radio telescope, detailing its technical specifications, observational capabilities, and unique advantages in low-frequency pulsar observations. Lastly, it reviews and summarizes RFI mitigation methods in radio astronomy, analyzing the limitations of existing technologies and identifying the key issues this thesis aims to address. In particular, current RFI mitigation methods often lead to the deletion of data identified as affected by RFI, which inevitably results in a loss of valuable information.In the second part of this thesis, we first present a simulation framework designed to generate RFI-corrupted pulsar observation data. The main goal of this framework is to build a dataset that allows the training of deep learning models, thus circumventing the recurring lack of properly labeled real data.After a thorough review of deep learning and convolutional neural networks, we highlight the shortcomings of existing RFI processing methods, which typically involve identifying and removing data suspected of being corrupted by RFI. To avoid this information loss and address this challenge, we propose a novel approach that consists in formulating the RFI attenuation problem as an image restoration task, aiming at reconstructing RFI-altered signals. Capitalizing on recent advances in deep learning, we show that this task can be efficiently achieved using a network, named RFI-DRUnet, whose architecture is inspired by a high-performance denoising network.In the following chapters, we illustrate the applicability and effectiveness of the proposed approach on simulated and real pulsar observation data, comparing it to current approaches based on deep convolutional neural networks that detect RFI. The results show that the proposed method can effectively restore RFI-corrupted observational signals under various conditions. Furthermore, we discuss the potential impact of this method for improving pulsar chronometry
Kahane, Claudine. „Observations millimétriques de molécules circumstellaires : de la recherche de nouvelles espèces, à la mesure d'abondances isotopiques“. Phd thesis, Grenoble 1, 1989. http://tel.archives-ouvertes.fr/tel-00724537.
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