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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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The link of education and popularization of astronomy with the choice of a future focus of study
Kříček, Radek ; Wolf, Marek (advisor) ; Kireš, Marián (referee) ; Štefl, Vladimír (referee)
This thesis provides an overview of Czech astronomy education both inside and outside of school environment and develops methods to explore its possible influence on science career decision. A mixed approach was chosen for the research. Based on the first qualitative part, hypotheses and specified research questions were formulated. Consequently, the hypotheses were examined using questionnaires distributed to students of several Czech universities. However, the data analysis showed a variable stronger than involvement in astronomy education - the breadth of science interest. Possible practical outcomes and recommendations for future research are discussed.
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Basic historical milestones for defining the constellations
Pechman, Matouš ; Šolc, Martin (advisor) ; Wolf, Marek (referee)
- Basic historical milestones for defining constellations People have always been fascinated by the starry sky. At first stars were only small distant lights, though people had no idea how far these lights actually were. It was a long way to the form of constellations as know them now. It started from only the brightest stars, which were supposed to be placed on spherical surface and their placement was associated with different types of characters of ancient nations, animals and things from their daily life or old legends and led to a distribution of the heavenly sphere to 88 areas with exactly defined borders. All of that took thousands of years of work and observations of generations of astronomers, improvement of instruments to measurement and writing down the positions of the celestial bodies. Research of constellations has never been a mere description of reality, but it has always been reflected in the thoughts and views of the world of a given culture or civilization.
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Astronomical grounds of calendars in different historical periods and cultures
Hrůšová, Lucie ; Šolc, Martin (advisor) ; Wolf, Marek (referee)
The main goal of this work is to describe calendars of various countries, and that both calendars, which are used until these days, and calendars of perished civilizations or calendars, which were abandoned by their users because during ages they had preferred another calendar. This work is for everyone, who would like to be informed, how our calendar was originated, why he contains some things which are illogical from our point of view such as the irregularity of the length of months. It also tries to show the way how the calendars were created, how they were refinement, but also that the calendar we use most, the Gregorian calendar, is not still perfect. First chapter wants to explain to reader, what is the lunar, solar and lunisolar calendar. In second chapter are described calendars of the eldest known Mediterranean civilizations in the context of antique literary creation. Third chapter is dedicated to the world's most widespread Gregorian calendar, the circumstances of his rise by correcting the Julian calendar, about his acceptance in world and about the lunar point in this otherwise solar calendar, namely the calculation of Easter. The fourth chapter is dealing with the newer calendars, which was tried to enter into force by revolutionary minded persons. And the last, the fifth, chapter is...
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A new spectroscopic study of the eclipsing binary V1143 Cyg
Jonák, Juraj ; Harmanec, Petr (advisor) ; Wolf, Marek (referee)
Using multiple red spectra of the eclipsing binary V1143 Cyg obtained between the years 2015 and 2017 at the Observatory of Ondřejov and in 2008 and 2009 at the Lick observatory in USA, we calculated a more recent orbital solution using the method of Fourier spectra disentangling. These new data, in addition to previous spectroscopic and photometric measurements, span an observation period of almost a hundred years. Since this binary star is remarkable due to its high orbital excentricity, along with classical, a significant relativistic apsidal motion is present. Using the software PHOEBE and available data we calculated the value of the total apsidal motion as 9,8(3).10−5 deg.d−1 , which is in good agreement with previous works. 1
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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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