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Quasar accretion disk mapping by gravitational microlensing
Ledvina, Lukáš ; Heyrovský, David (advisor) ; Horák, Jiří (referee)
Quasar microlensing is a relatively newly explored phenomenon, which is ideally suited for studying the spatial distribution of emission from the innermost accretion disc. By now we know many macrolensed quasars, in which we can observe multiple images formed by the deflection of light in the gravitational field of an intervening galaxy. In case one of these images passes directly through the stellar population of the galaxy, it can be additionally microlensed by individual stars. The gravitational field of these stars forms a caustic network for light passing by. When a quasar accretion disc crosses behind this network, induced changes can be observed in the light curve as well as in the spectrum. In the first part of this thesis we study the statistics of the time intervals between successive caustic crossings. In the second part we use a fully relativistic Kerr-metric thin-disc model for studying the light curve of a fold-caustic crossing and its dependence on the accretion- disc parameters. In the last part we simulate changes in the X-ray iron-line profile during a fold-caustic crossing. We find characteristic spectral features formed on the line, and derive their analytical description. Finally, we map the maximum strength of microlensing-generated peaks on the spectral line for different...
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Measuring accretion disk properties from quasar microlensing
Ledvina, Lukáš ; Heyrovský, David (advisor) ; Dovčiak, Michal (referee)
When we observe a~distant quasar through an intervening galaxy we may see a~number of observable images caused by hte deflecton of light in galaxy's gravitational field. If an image passes through the stellar population of the galaxyit can be additionally microlensed by individual stars. In this work we first compute microlensing magnification maps for a~point source. We than use these maps to determine light curves for extended source, namely for a~quasar accretion disc.In the second part we compare obtained light curves for different discs and we will study the influence of inclination, orientation and surface brightness distribution of an accretion disk on the light curve during an individual crossing of a~cusp and fold of microlensing custic network
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Quasar accretion disk mapping by gravitational microlensing
Ledvina, Lukáš ; Heyrovský, David (advisor)
Quasar microlensing is a relatively newly explored phenomenon, which is ideally suited for studying the spatial distribution of emission from the innermost accretion disc. By now we know many macrolensed quasars, in which we can observe multiple images formed by the deflection of light in the gravitational field of an intervening galaxy. In case one of these images passes directly through the stellar population of the galaxy, it can be additionally microlensed by individual stars. The gravitational field of these stars forms a caustic network for light passing by. When a quasar accretion disc crosses behind this network, induced changes can be observed in the light curve as well as in the spectrum. In the first part of this thesis we study the statistics of the time intervals between successive caustic crossings. In the second part we use a fully relativistic Kerr-metric thin-disc model for studying the light curve of a fold-caustic crossing and its dependence on the accretion- disc parameters. In the last part we simulate changes in the X-ray iron-line profile during a fold-caustic crossing. We find characteristic spectral features formed on the line, and derive their analytical description. Finally, we map the maximum strength of microlensing-generated peaks on the spectral line for different...
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Quasar accretion disk mapping by gravitational microlensing
Ledvina, Lukáš ; Heyrovský, David (advisor)
Quasar microlensing is a relatively newly explored phenomenon, which is ideally suited for studying the spatial distribution of emission from the innermost accretion disc. By now we know many macrolensed quasars, in which we can observe multiple images formed by the deflection of light in the gravitational field of an intervening galaxy. In case one of these images passes directly through the stellar population of the galaxy, it can be additionally microlensed by individual stars. The gravitational field of these stars forms a caustic network for light passing by. When a quasar accretion disc crosses behind this network, induced changes can be observed in the light curve as well as in the spectrum. In the first part of this thesis we study the statistics of the time intervals between successive caustic crossings. In the second part we use a fully relativistic Kerr-metric thin-disc model for studying the light curve of a fold-caustic crossing and its dependence on the accretion- disc parameters. In the last part we simulate changes in the X-ray iron-line profile during a fold-caustic crossing. We find characteristic spectral features formed on the line, and derive their analytical description. Finally, we map the maximum strength of microlensing-generated peaks on the spectral line for different...
|
|
|
Quasar accretion disk mapping by gravitational microlensing
Ledvina, Lukáš ; Heyrovský, David (advisor) ; Horák, Jiří (referee)
Quasar microlensing is a relatively newly explored phenomenon, which is ideally suited for studying the spatial distribution of emission from the innermost accretion disc. By now we know many macrolensed quasars, in which we can observe multiple images formed by the deflection of light in the gravitational field of an intervening galaxy. In case one of these images passes directly through the stellar population of the galaxy, it can be additionally microlensed by individual stars. The gravitational field of these stars forms a caustic network for light passing by. When a quasar accretion disc crosses behind this network, induced changes can be observed in the light curve as well as in the spectrum. In the first part of this thesis we study the statistics of the time intervals between successive caustic crossings. In the second part we use a fully relativistic Kerr-metric thin-disc model for studying the light curve of a fold-caustic crossing and its dependence on the accretion- disc parameters. In the last part we simulate changes in the X-ray iron-line profile during a fold-caustic crossing. We find characteristic spectral features formed on the line, and derive their analytical description. Finally, we map the maximum strength of microlensing-generated peaks on the spectral line for different...
|
|
|
Measuring accretion disk properties from quasar microlensing
Ledvina, Lukáš ; Heyrovský, David (advisor) ; Dovčiak, Michal (referee)
When we observe a~distant quasar through an intervening galaxy we may see a~number of observable images caused by hte deflecton of light in galaxy's gravitational field. If an image passes through the stellar population of the galaxyit can be additionally microlensed by individual stars. In this work we first compute microlensing magnification maps for a~point source. We than use these maps to determine light curves for extended source, namely for a~quasar accretion disc.In the second part we compare obtained light curves for different discs and we will study the influence of inclination, orientation and surface brightness distribution of an accretion disk on the light curve during an individual crossing of a~cusp and fold of microlensing custic network
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