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Distance to the Magellanic clouds
Kulich, Matúš ; Zasche, Petr (advisor) ; Korčáková, Daniela (referee)
Twelve eclipsing binary systems from the region of the Large Magellanic Cloud have been studied in this thesis in order to calculate the distance. The photometric data come from the OGLE survey carried out at the Las Campanas Observatory in Chile and the spectroscopic data come from other papers where they had already been partially ana- lyzed for other purposes. From these data, the light curves and the radial velocity curves of these systems have been constructed and analyzed using the PHOEBE soft- ware, in which the physical parameters and the absolute magnitudes of their individual components have been determined by the method of synthetic curves. By comparing them to the observed apparent magnitudes in I-band deduced from the light curves and taking into account the bolometric corrections and the V-I indices, the distance modu- lus of the Large Magellanic Cloud could be determined to be 18.59 ± 0.4 mag, which fairly corresponds to the quite familiar results determined by using this and other meth- ods in various research papers. However, in order to determine the distance modulus more accurately, it would be necessary to use accurate, much more complex models of stellar atmospheres and not simply rely on the general relations of the main-se- quence stellar parameters, which exhibit quite a large variance.
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Study of connection between period changes and spectral type in eclipsing binaries
Vyhnálková, Veronika ; Zasche, Petr (advisor) ; Wolf, Marek (referee)
Main aim was to study whether there is a correlation between the changes in the period of the eclipsing binary stars and the spectral type of their secondary components. In the course of this thesis the character of period changes based on O-C diagrams is studied. Obtaining necessary data, several diagrams were constructed, namely the dependence of the mass ratio of both components (or period) for the effective temperature of the secondary, and another for various star type and lenght of measurement. From these diagrams the absence of alterning period change of the binaries with hot secondary was not proved, but it is indicated the shift of temperature of secondaries for binaries with increase (decrease) period to higher (lower) values. Also it was showed that monotone period changes are approximately twice more frequent for β Lyrae and W UMa-type stars than for Algols.
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Pulsating components in binaries
Korda, David ; Zasche, Petr (advisor) ; Wolf, Marek (referee)
In the beginning there are introduced the binaries and pulsating stars. The main aim of the present work was the study of Delta Scuti stars within the eclipsing binaries. In particular, observing the stellar system V389 Cas at Ondrejov observatory, reduction of the CCD images with the program MuniWin, and analysis of the light curve with program Phoebe. From the residuals of the light curve there were studied the pulsations by the program Period04, resulting in its pulsational period. The relation between both periods - orbital and pulsational - was studied by means of the already known systems, including the theoretical relation and location of the star V389 Cas in the period-period diagram. 1
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