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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)
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A new study of the long-term and orbital variations of the Be star V923 Aql
Steiner, Michal ; Harmanec, Petr (advisor) ; Wolf, Marek (referee)
The first part of this thesis deal with the topic of Be stars, their variability on different time scales and some of the models explaining formation of the envelope. Next part deals with software, which is used for measurement. After introduction to these programs the data analysis follows. Overall, 46 spectra from Ondřejov Observatory and Hvar photometric observations that covered time RJD=52000- 58500 has been used. Each finding were compared with already known properties of V923Aql. Most behavior patterns that were seen in the past has been seen even in the available data, but a difference between RVHα and RVM measured on metallic lines were found. Also, the length of long-term cycle seems to differ from that in the past cycles. 1
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Flare stars
Kára, Jan ; Wolf, Marek (advisor) ; Švanda, Michal (referee)
The works deals with the study of the flare stars, which is a group of stars for which sudden brightening can be observed. The work focuses on a star GJ 3236, which is a low-mass eclipsing binary and on which numerous flares have been observed. For the analysis of this system spectroscopic and photometric data were used, which were obtained at various observatories. Parameters of the binary system have been determined by analysing spectroscopic and photometric data with the program PHOEBE. A total of 241 flares have been detected in the photometric data and for 190 flares, which light curves were not affected by eclipses, released energies were estimated. The set of flares was used for the study of stellar activity of the binary. The energy distribution of observed flares is similar to the flares observed on other flare stars and also on the Sun. This suggests, that the flare mechanism is the same for these stars.
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