National Repository of Grey Literature 12 records found  1 - 10next  jump to record: Search took 0.00 seconds. 
The light curves of eclipsing binaries
Korda, David ; Zasche, Petr (advisor)
New CCD photometric observations of ten short-period LMB (Low Mass Binaries) were carried out. Data were obtained using 65 cm telescope in Ondrejov in the filters I, R and V from 2014 to 2016. Light curves were analysed using the program PHOEBE. The obtained masses and radii of the stars were compared with the theoretical mass-radii relation. There arises that the short-period binaries have the radii of about 4 % larger than the theoretical prediction from the stellar evolution models. 1
Photometric analysis of CzeV371
Sedláčková, Eva ; Zasche, Petr (advisor) ; Korčáková, Daniela (referee)
The thesis focuses on the analysis of the light curve of eclipsing binary called CzeV 371 Aur by program PHOEBE. The data were collected during five years, each season is analysed separately. This binary is a detached system consisting of two main sequence stars of the spectral type K with the period of 0,90696 days. Other parameters of this system are the inclination i = 85, 19◦ or the tem- perature of the secondary component T2 = 4060 K assuming the temperature of the primary component T1 = 4200 K. This system is interesting for asym- metries on the light curve, which are changing during the years. These can be interpreted as a spot on the primary compoment. According to the character and the rate of its changes, we can say that it is probably not the same spot in all seasons, but it is rather a group of smaller short-lived spots. 1
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.
CCD photometry of variable objects in nearby galaxies
Kára, Jan ; Wolf, Marek (advisor) ; Zasche, Petr (referee)
The work concerns the study of variable stars in the Small Magellanic Cloud with use of time series of photometric images of star field NGC 330, which were obtained by the 1,54-m Danish telescope at the observatory La Silla in Chile during years 2012 - 2016. The aim of this work is to produce light curves of variable stars a to determine their period of variability assuming the variations are periodical. For some stars data from earlier published papers were used, which led to the coverage of longer period of time and therefore to the improvement of the accuracy of the period determination. The work lists summary of some of the types of variable stars and of mechanisms causing their variability. The work focus mainly on cepheids, which can be used to determine distances in the Universe thanks to the relation between their absolute magnitude and period of pulsation.
Study of inclination change for the eclipsing binaries
Juryšek, Jakub ; Zasche, Petr (advisor) ; Brož, Miroslav (referee)
This thesis deals with the study of the eclipsing binaries with inclination changes, caused by orbital precession due to third body in the system. Methods of semiauthomatic detection of the inclination changing eclipsing binaries among huge lightcurves databases have been developed. These methods have been applied to the ASAS-3 and OGLE III LMC databases. As a result, 39 new systems suspected of orbital precession have been found and 33 of them are situated in the Large Magellanic Cloud, with only one previously studied system. Increasing the number of known multiple systems especially those located outside Milky Way allows to study inter-galactic differences in star formation. In this work, we bring detailed study of ten new systems and restrictions on the third body parameters are presented. Powered by TCPDF (www.tcpdf.org)
The light curves of eclipsing binaries
Korda, David ; Zasche, Petr (advisor) ; Wolf, Marek (referee)
New CCD photometric observations of ten short-period LMB (Low Mass Binaries) were carried out. Data were obtained using 65 cm telescope in Ondřejov in the filters I, R and V from 2014 to 2016. Light curves were analysed using the program PHOEBE. The obtained masses and radii of the stars were compared with the theoretical mass-radii relation. There arises that the short-period binaries have the radii of about 4 % larger than the theoretical prediction from the stellar evolution models. Powered by TCPDF (www.tcpdf.org)
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
The light-curve solution of an eclipsing binary
Procházka, Ondřej ; Zasche, Petr (advisor) ; Wolf, Marek (referee)
The main aim of this work was the first detailed analysis of an eclipsing binary system V641 Aur. The complete light curve of this binary was obtained in three photometric filters, which were analyzed with the program PHOEBE. It is a double star with the orbital period of about 0.50487 day, whose both components are rather similar. Their individual spectral types are probably F6 and F8 (according to the temperatures), or F6 and F6 (as derived from masses). Both are orbiting on a circular orbit and despite their short period the system is a detached one and both components are still located on the main sequence. Moreover, thanks to the asymmetry of the light curve there was discovered a spot on the surface of the primary component, and the third light was not detected. For more detailed analysis higher accuracy of photometry and spectroscopy data are required.
The evolution of stars with various masses
Cibulková, Helena ; Brož, Miroslav (advisor) ; Zasche, Petr (referee)
In the present work we study changes of the structure of a star that occur during stellar evolution and the dependence of these changes on the initial mass of the star. Internal changes affect also characteristics of the star which are observable from the outside like the effective tempe- rature or luminosity. At first we briefly derive basic equations of the stellar structure which describe the most important processes inside the star. We assume the star is nonrotating and spherically symmetric. For a detailed description of the stellar evolution, we plot individual quantities for different initial masses (from 0,1 to 100 M⊙). We use the program EZ2 for numerical calculations which enables to model the stellar evolution as long as the condition of the hydrostatistic equilib- rium is satisfied. Finally, we use the theory of the stellar evolution to determine the ages of two open clusters NGC 188 and M 45 using the method of isochrones. Keywords: stellar evolution, Hertzsprung-Russell diagram, equations of stellar structure, pro- gram EZ2 1

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