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Particle motion in the vicinity of compact stellar objects
Čechura, Jan ; Hadrava, Petr (advisor) ; Šubr, Ladislav (referee)
In this thesis we discuss the properties of a radiation-driven stellar wind in an X-ray binary system. Using the parameters appropriate for the high mass Xray binary system Cygnus X-1, the effects of the compact companion on the stellar wind are examined. We have developed a full 3D hydrodynamic model of circumstellar mass based on a modified version of the Castor, Abbott & Klein line-driven mechanism. The effects of the compact companion - gravity and continuum radiation pressure - as well as the centrifugal and Coriolis force due to orbital motion are included. These forces subvert the spherical symmetry of the wind and lead to significantly different results then previous strictly radial hydrodynamic simulations.
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Physics of X-ray binaries
Čechura, Jan
Title: Physics of X-ray binaries Author: Jan Čechura Department: Astronomical Institute of the Academy of Sciences of the Czech Republic Supervisor: doc. RNDr. Petr Hadrava, DrSc. Abstract: We present a novel observation interpreting method for the high-mass X-ray binaries (HMXBs) based on a combination of spectroscopic data and numerical results of a radiation hydrodynamic model of stellar wind in HMXBs. By using an indirect imaging method of Doppler tomography, we calculate synthetic tomograms of a predicted emission in Low/Hard and High/Soft X-ray states and compare them with tomograms produced using phase-resolved optical spectra of Cygnus X-1, a prototype of HMXBs. The emis- sions of HMXBs are determined by the local conditions within the circumstellar medium - namely by local density, temperature, and ionization parameter. These quantities are computed by the radiation hydrodynamic code and strongly depend on the X-ray state of such systems. By increasing intensity of an X-ray emission produced by the compact companion in the HMXB-model, we achieved a complete redistribution of the circumstel- lar medium in the vicinity of the modelled system. These changes (which simulate the transitions between two major spectral states) are also apparent in the synthetic Doppler tomograms which are in a good...
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Physics of X-ray binaries
Čechura, Jan ; Hadrava, Petr (advisor) ; Heyrovský, David (referee) ; Krtička, Jiří (referee)
Title: Physics of X-ray binaries Author: Jan Čechura Department: Astronomical Institute of the Academy of Sciences of the Czech Republic Supervisor: doc. RNDr. Petr Hadrava, DrSc. Abstract: We present a novel observation interpreting method for the high-mass X-ray binaries (HMXBs) based on a combination of spectroscopic data and numerical results of a radiation hydrodynamic model of stellar wind in HMXBs. By using an indirect imaging method of Doppler tomography, we calculate synthetic tomograms of a predicted emission in Low/Hard and High/Soft X-ray states and compare them with tomograms produced using phase-resolved optical spectra of Cygnus X-1, a prototype of HMXBs. The emis- sions of HMXBs are determined by the local conditions within the circumstellar medium - namely by local density, temperature, and ionization parameter. These quantities are computed by the radiation hydrodynamic code and strongly depend on the X-ray state of such systems. By increasing intensity of an X-ray emission produced by the compact companion in the HMXB-model, we achieved a complete redistribution of the circumstel- lar medium in the vicinity of the modelled system. These changes (which simulate the transitions between two major spectral states) are also apparent in the synthetic Doppler tomograms which are in a good...
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Physics of X-ray binaries
Čechura, Jan
Title: Physics of X-ray binaries Author: Jan Čechura Department: Astronomical Institute of the Academy of Sciences of the Czech Republic Supervisor: doc. RNDr. Petr Hadrava, DrSc. Abstract: We present a novel observation interpreting method for the high-mass X-ray binaries (HMXBs) based on a combination of spectroscopic data and numerical results of a radiation hydrodynamic model of stellar wind in HMXBs. By using an indirect imaging method of Doppler tomography, we calculate synthetic tomograms of a predicted emission in Low/Hard and High/Soft X-ray states and compare them with tomograms produced using phase-resolved optical spectra of Cygnus X-1, a prototype of HMXBs. The emis- sions of HMXBs are determined by the local conditions within the circumstellar medium - namely by local density, temperature, and ionization parameter. These quantities are computed by the radiation hydrodynamic code and strongly depend on the X-ray state of such systems. By increasing intensity of an X-ray emission produced by the compact companion in the HMXB-model, we achieved a complete redistribution of the circumstel- lar medium in the vicinity of the modelled system. These changes (which simulate the transitions between two major spectral states) are also apparent in the synthetic Doppler tomograms which are in a good...
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Particle motion in the vicinity of compact stellar objects
Čechura, Jan ; Šubr, Ladislav (referee) ; Hadrava, Petr (advisor)
In this thesis we discuss the properties of a radiation-driven stellar wind in an X-ray binary system. Using the parameters appropriate for the high mass Xray binary system Cygnus X-1, the effects of the compact companion on the stellar wind are examined. We have developed a full 3D hydrodynamic model of circumstellar mass based on a modified version of the Castor, Abbott & Klein line-driven mechanism. The effects of the compact companion - gravity and continuum radiation pressure - as well as the centrifugal and Coriolis force due to orbital motion are included. These forces subvert the spherical symmetry of the wind and lead to significantly different results then previous strictly radial hydrodynamic simulations.
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Analysis of Positiong of Brand Flora
Křížová, Lenka ; Lhotáková, Markéta (advisor) ; Čechura, Jan (referee)
The main aim of this thesis is to analyze the positioning of Flora brand on the czech market. For my analysis I will use the chosen marketing tools such as the competitor analysis, SWOT analysis so as the analysis of marketing mix. The key source of information will be the qualitative research. On the basis of that I will compare the ideal positioning with the real one and come with the appropriate suggestions which could help to improve the positioning strategy of Flora brand in the Czech republic.
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