Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 28 for “"X-ray observations"”.
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Stellar Energy Feedback in Superbubbles
"In the first study of this thesis, optical and X-ray observations have been used to probe the nature of the ultraluminous supernova remnant (SNR) MF16 in NGC6946 and explore a single star's interaction with the ISM. The second study presents observations of diffuse X-ray emission from the …
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Long-term properties of X-ray binaries in the magellanic clouds
Long-term variability in all types of X-ray binaries is a well established characteristic, but due to observation limitations and lack of long-term monitoring capability these variations have not been studied before in a systematic way. In this thesis, we exploit the ~ 16 yr optical light curves …
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Electron acceleration in a flare plasma via coronal circuits
… of the Sun's secrets by using high resolution observations and describing the Sun by means of models. As an active star the Sun's activity, as expressed in its magnetic cycle, is closely related to the sunspot numbers. Flares play a special role, because they release large energies on very …
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Properties of gas and dark matter in X-ray galaxy clusters with Sunyaev Zel'dovich measurements
… entropy profiles obtained in a sample of 24 X-ray objects at high redshift retrieved from the Chandra archive. I have discussed the scaling properties of the entropy S, the correlation between metallicity Z and S, the profiles of the temperature of the gas, Tgas, and performed a comparison …
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Weak lensing flexion as a probe of galaxy cluster substructure
… of optical imaging, spectroscopy, and X-ray observations I determine that the cluster RCS043938-2904.7, while apparently anomalous initially due to its high optical richness and low X-ray surface brightness, is in fact an association of structures along the line of sight. Accounting for …
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Radiative signatures of the jet launching region in astronomical objects
… hole systems, from stellar-mass black holes in X-ray binaries (XRBs), to supermassive black holes in active galactic nuclei (AGN). However, despite decades of observational and theoretical research, the mechanism by which relativistic jets are launched in nature remains one of the most important …
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Gravitational waves: understanding black holes
This thesis concerns the use of observations of gravitational waves as tools for astronomy and fundamental physics. Gravitational waves are small ripples in spacetime produced by rapidly accelerating masses; their existence has been predicted for almost 100 years, but the first direct evidence of …
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X-ray spectroscopic and timing studies of galactic black hole binaries
In rare cases, optical observations of Galactic binary star systems which are bright in the X-ray portion of the electromagnetic spectrum dynamically constrain the mass of one component to be well above theoretical limits for a neutron star. These systems - and systems with similar X-ray properties …
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X-ray Studies of the Innermost Regions of Black Hole Accretion
… I present the results of my research on the X-ray spectra of accreting black holes. The content of this thesis can be broadly separated into two parts: Chapter 2-3 for stellar-mass black holes in X-ray binaries (XRBs) and Chapter 4-6 for supermassive black holes in active galactic nuclei (AGN). …
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Mass profiles of clusters of galaxies : a comparison of X-ray and weak lensing observations
… a detailed comparison of mass estimates from X-rays and weak gravitational lensing for a sample of 32 intermediate low redshift clusters, and study the dependence of the mass profiles derived from these techniques on the dynamical state of the clusters. We analyze Chandra X-ray observations and …
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HETE, the High Energy Transient Explorer : unlocking the mysteries of gamma ray bursts
… in October 2000 with the goal of studying Gamma Ray Bursts (GRBs) at X-ray and gamma-ray energies. A suite of instruments aboard HETE provide broadband sensitivity to GRBs: the French Gamma Telescope (FREGATE; 6 keV to > 400 keV ) instrument provides sensitive detections at gamma-ray energies, …
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X-ray spectroscopy of neutron star low-mass X-ray binaries
… of topics relating to neutron star lowmass X-ray binaries (LMXBs) and utilize spectral information from X-ray observations to further our understanding of these sources. First, I give an overview of important X- ray astrophysics relevant to the work I present in subsequent chapters, as well as …
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Machine learning from hard x-ray surveys: applications to magnetic cataclysmic variable studies
… the production of unbiased future soft gamma-ray source catalogues. The feature extraction process on an initial candidate list is described together with feature merging. Three trainng and testing sets are created in order to deal with the diverse time-scales encountered when dealing with the …
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Mass transfer and accretion in the eccentric neutron-star binary Circinus X-1
… series of observational studies with the Rossi X-ray Timing Explorer satellite and through theoretical computer models I developed to explore mass transfer and evolution in an eccentric binary. We also organized two multi-frequency campaigns to study correlated variability in different frequency …
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Monte-Carlo simulations of globular cluster dynamics
… available from the latest optical, radio, and X-ray observations of globular clusters by various satellites and ground-based observatories, and in part by recent advances in computer hardware. New parallel supercomputers, combined with improved computational methods, now allow us to perform …
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Multiwavelength Studies of Rotating Radio Transients
… those other neutron star populations like the X-ray bright magnetars. However, some of the RRATs have spin-down properties very similar to those of normal pulsars, making it difficult to determine the cause of their unusual emission and possible evolutionary relationships between them and other …
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Simulating the dynamical evolution of galaxies in group and cluster environments
… environments. The presence of long-lived, hot X-ray emitting coronae observed in a large fraction of group and cluster galaxies is not well-understood. These coronae are not fully stripped by ram pressure and tidal forces that are efficient in these environments. Theoretically, this is a …
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Unveiling fundamental physics with high-resolution X-ray spectroscopy of Active Galactic Nuclei.
… flow onto SMBHs in AGNs as revealed by X-ray observations of AGNs. This is followed with a discussion on the use of X-ray reflection spectroscopy as a probe of the spin of moderately accreting SMBHs, and the use of spin diagnostics to probe the growth of SMBHs over cosmic timescales. …
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Understanding X-ray reflection as a probe of accreting black holes
The reflection of the X-rays emitted from a corona of energetic particles surrounding an accreting black hole from the accretion disc is investigated in the context of probing the structure of the central regions as well as the physical processes that power some of the brightest objects seen in the …
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The binary system containing the pulsar PSR 1913+16 and ultra-violet and x-radiation from accreting magnetic white dwarfs
… actually emitted at low harmonics is theref0re a Raylejgh-Jeans spectrum with a brightness temperature equal to that of the electrons. At an energy E ranging from a few eV to a few. tens of eV, the cyclotron spectrum becomes optically thin and falls rap:idly with increasing energy. In order to …
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