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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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Exoplanets
Kliner, Jiří ; Wolf, Marek (advisor) ; Šolc, Martin (referee)
In this diploma thesis is contained an overview of the current knowledge about extrasolar planets and especially the overview of the current techniques of their detection. It was observed one full transit of the star TrES-1 by a exoplanet on the 65cm telescope on Ondoejov. It was only the second observation the transit from the Czech Republic. It was estimated the parameters of the system and compared with as yet publicated values.
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Analysis of doubly eclipsing system
van Overloop, Samuel ; Zasche, Petr (advisor) ; Wolf, Marek (referee)
The thesis focuses on selection and analysis of a candidate for a doubly eclipsing system in the Small Magellanic Cloud and on proving its quadruple nature. The OGLE- SMC-ECL-1758 system with periods P1 = 0.92917 d and P2 = 3.73518 d was chosen. The PHOEBE program allowed us to analyse light curves of both eclipsing binaries and determine their parameters such as inclination, surface potencials or the ratio of luminosities. Using these light curves we derived times of eclipses on data from catalogues OGLE II-IV searched for their ETV variations. Thanks to O-C analysis we found proof of relative motion of the two eclipsing binaries around a common centre of mass. Therefore, the OGLE-SMC-ECL-1758 system most probably is a quadruple doubly eclipsing system with a lower limit for its period P = 6021 d. 1
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Distance to nearby galaxies
Šándorová, Ivana ; Zasche, Petr (advisor) ; Wolf, Marek (referee)
Title: Distance to nearby galaxies Author: Ivana Šándorová Institute: Astronomical Institute of the Charles University Supervisor: doc. RNDr. Petr Zasche, Ph.D., Astronomical Institute of the Charles University Abstract: The present work is focused on the study of the variable stars, particularly the lumi- nosity of cepheids in The Large Magellanic Cloud. The data were obtained from photometric observations of starfield (image centre coordinates: RA: 5◦13 36 , DE: −69h 22m 42s) using the 1,54 m Danish telescope at the observatory La Silla in Chile. The aim of this work was to find the distance of Large Magellanic Cloud, which was determined by the "period - lu- minosity relation" method for cepheids. We studied 13 cepheids, which were compared with one non-variable star. We computed the average value of distance modulus as (18,42 ± 0,40) mag. The distance modulus from the latest publication (Pietrzi'nski, G. and others, 2019) is (18,477 ± 0,004 (statistic) ± 0,026 (systematic)) mag. SIPS (Scientific Image Processing System) is software for measuring and processing of images of star field and was used in this work for processing of photometric images of star field. Own program was used for creating and editing the light curves. Keywords: galaxy, variable stars, cepheids, distance modulus 1
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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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