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 25 for “"accretion flow"”.
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Relativistic Radiative Hydrodynamics Calculation of Accretion Flow into Supermassive Black Hole
… for explanation, and structure of innermost accretion flow not yet well constrained, the understanding of accretion into Sgr A* demands advances in both theories and computational calculation. To increase the understanding of Sgr A* in particular, and low-luminosity active galactic nuclei in …
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Type I X-ray bursts as probes of the neutron star accretion flow
… also includes the emission of the neutron star accretion flow. X-ray bursts irradiate it, leading to structural and emission changes. Therefore, understanding the evolution of the accretion flow emission not only allows us to constrain neutron star properties but also to probe its accretion …
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Local Numerical Models of Turbulent Accretion Flows
… for driving angular momentum transport in accretion disks. This work provides a comprehensive study of MHD turbulent accretion flow using shearing box simulations.
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Accretion flows and neutron star heating in low-mass X-ray binaries
… excellent test beds for studies of high-energy accretion flows and the properties of compact objects. Neutron star (NS) low-mass X-ray binaries (LMXBs) vary in brightness by almost 8 orders of magnitude and are hosts to diverse accretion flows, transporting varying amounts of energy and mass …
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On electromagnetic observables from supermassive black hole accretion flows
… start with a review of astrophysical black hole accretion systems and the radiative physics that governs the generation of electromagnetic signals from hot leptons near the hole. I then describe the numerical tools I use to simulate the accretion and generate synthetic images and spectra, paying …
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The evolution of the first stellar systems
… focus on the small scale physics during the the accretion phase. We first provide an analytic understanding of the thermodynamics and the fragmentation condition of the primordial accretion flow. Unsurprisingly, fragmentation is more likely to take place at r >~ 10 au due to a lower optical depth …
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Black Hole Accretion Systems
"Accretion onto a black hole is the most efficient known process to convert gravitational energy into radiation. Some gamma-ray bursts (GRBs), some X-ray binaries, and all active galactic nuclei (AGN) are likely powered by accretion onto a rotating black hole. I model the global, timedependent …
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The motion of stars and the accretion of matter in the fermion ball and black hole scenarios of the galactic centre
… It should be noted that Advection Dominated Accretion Flow models (not investigated here) are able to predict the observed spectrum for the black hole scenario.
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Constraining the Initial Conditions and Final Outcomes of Accretion Processes around Young Stars and Supermassive Black Holes
… to planet formation. My work revealed episodic accretion onto the more massive component of the pre-main sequence binary system UY Aur. I also showed changes in the accretion onto the less massive component, revealing contradictory indications of the change in accretion rate when considering …
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Reverberation Mapping of Supermassive Black Holes using Machine Learning
… (AGN), offer a unique window into the physics of accretion and feedback that shape galactic evolution. Yet, the small spatial scales of these regions remain inaccessible to direct imaging. Reverberation mapping circumvents this limitation by using time delays between correlated emission at …
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Radiative signatures of the jet launching region in astronomical objects
… the radiative properties of the inner accretion flow and jet launching region in a range of low-luminosity accreting black hole systems. We treat the plasma dynamics using sophisticated general-relativistic magnetohydrodynamic simulations, and calculate the resulting spectral and …
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Time-dependent Accretion Flows onto Black Holes
Accretion onto compact objects plays a fundamental role in a number of astrophysical systems like active galactic nuclei (AGN) and black hole X-ray binaries (BHXB). The standard thin disk model fails to reproduce the spectra of these systems. They exhibit a blackbody-like component, generally …
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Magneto-centrifugal Wind with Applications to Astrophysical Accretion Disks
… gravity, and to drive a magneto-centrifugal outflow. Taking into account cosmic ray ionization, streaming, injection from massive stars and energy losses, we calculate the transition from a hydrostatic disk to an outflowing wind. The solutions are constrained by the slow-magnetosonic critical …
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Disk-magnetosphere interaction in X-ray binaries
… through the line of sight. In many systems, accretion proceeds via a Keplerian accretion disk. The differential rotation of the disk and star creates magnetic stresses that disrupt the Keplerian flow, and bring the plasma into corotation with the neutron star well above the stellar surface. …
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Merging black hole binaries in gaseous environments: simulations in general-relativistic magnetohydrodynamics
… radiation, as the stirring, shock heating and accretion of the gas may produce variability and enhancements in the electromagnetic flux. This can provide a wealth of opportunities to study gravitational physics, accretion physics, and cosmology. We investigate this scenario by performing fully …
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The magnetospheres of accreting neutron stars
Accretion onto compact objects may power some compact X-ray sources. In the present study, we develop further the theory of accretion onto magnetic neutron stars in the particular case when the accretion flow is radial and the neutron star is slowly rotating. We examine in detail the formation and …
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Studying Accretion Disc Winds with X-ray Spectroscopy
… results of my PhD research into the physics of accretion (infall) and ejection (outflow) of matter in compact objects. Accretion disc winds are formed of hot and ionised material launched by magnetic forces, radiation pressure or thermally from the discs of accretors. They have been discovered …
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Unveiling fundamental physics with high-resolution X-ray spectroscopy of Active Galactic Nuclei.
… account of the knowledge of the physics of the accretion 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 …
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Broad-band spectral analysis of a complete sample of type 1 AGN detected by INTEGRAL
… a jet but rather a different geometry and/or accretion flow efficiency in the accretion disk. The analysis of the complete sample of type 1 AGN also allows a general picture of the average properties of this class of sources to be obtained. The mean power law slope is found to be ?=1.86±0.01, …
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