National Repository of Grey Literature 53 records found  1 - 10nextend  jump to record: Search took 0.00 seconds. 
Cataclysmic variable stars
Kára, Jan ; Wolf, Marek (advisor) ; Szkody, Paula (referee) ; Mennickent, Ronald (referee)
Cataclysmic variable stars are semi-detached binary systems consisting of a white dwarf primary star and a late-type secondary star. The secondary star in these systems is over- filling its Roche lobe, which enables a mass transfer to occur between the components. The transferred matter forms an accretion disc around the white dwarf when no strong magnetic field is present. This thesis presents a study of four different cataclysmic variables using light-curve modelling of eclipses and Doppler tomography as the main methods of analysis. The systems selected for the study belong to different subtypes of cataclysmic variables, but all of them exhibit mass-transfer rates which put them close to a border between systems with stable and unstable accretion disc. Although each of the systems studied represents a different type of cataclysmic variables, the presented study shows that they share some common characteristics and that the study of such systems is important for understanding the evolution of cataclysmic variables and the physical processes connected with them.
Cataclysmic variable stars
Kára, Jan ; Wolf, Marek (advisor)
Cataclysmic variable stars are semi-detached binary systems consisting of a white dwarf primary star and a late-type secondary star. The secondary star in these systems is over- filling its Roche lobe, which enables a mass transfer to occur between the components. The transferred matter forms an accretion disc around the white dwarf when no strong magnetic field is present. This thesis presents a study of four different cataclysmic variables using light-curve modelling of eclipses and Doppler tomography as the main methods of analysis. The systems selected for the study belong to different subtypes of cataclysmic variables, but all of them exhibit mass-transfer rates which put them close to a border between systems with stable and unstable accretion disc. Although each of the systems studied represents a different type of cataclysmic variables, the presented study shows that they share some common characteristics and that the study of such systems is important for understanding the evolution of cataclysmic variables and the physical processes connected with them.
Doubly-eclipsing systems
Šándorová, Ivana ; Zasche, Petr (advisor) ; Wolf, Marek (referee)
Title: Doubly-eclipsing systems Author: Bc. Ivana Šándorová Institute: Astronomical Institute of Charles University Supervisor: doc. RNDr. Petr Zasche, Ph.D., Astronomical Institute of Charles University Abstract: The study of doubly-eclipsing systems also brings new knowledge about quadru- ple stellar systems as such. And therefore the goal of our work was to create an algorithm for detecting candidates for doubly-eclipsing systems. We had photometric data avail- able from the OGLE project from the Small Magellanic Cloud. After evaluating all the data with our semi-automatic program we selected 74 objects which were further ana- lyzed in PHOEBE. We have obtained 11 new candidates for doubly-eclipsing systems for which we were able to derive both eclipse periods (other 15 candidates in SMC are already known). This gives us only 0.3 % of all binary stars in the SMC for candidates for doubly-eclipsing systems. Out of the 11 new candidates, we detected some variations indicating a common orbit for 6 of them based on the analysis of the O - C diagrams, namely: OGLE SMC-ECL-1086, OGLE SMC-ECL-2339, OGLE SMC-ECL-2515, OGLE SMC-ECL-3075, OGLE SMC-ECL-4756 and OGLE SMC-ECL-6093. Their mutual or- bital period was obtained in the range of 4 to 15 years. This means that these candidates are probably bound 2+2 systems....
Spectroscopic study of eccentric eclipsing binaries
Lipták, Jozef ; Wolf, Marek (advisor) ; Zasche, Petr (referee)
Close eccentric eclipsing binary star systems are important to our understanding of stellar formation and evolution. We analyze three such systems - V335 Ser, BW Boo and DR Vul - with emphasis on a possible third body in the systems needed for the system's existence according to the current theoretical models. Using spectra from the Ondřejov Observatory, we attempted to disentangle the spectra of the components and determine the radial velocity solutions for the systems. For V335 Ser we obtain new radial velocity measurements, spectra, and upper limits on the mass of a possible third body. For BW Boo we obtain the spectrum of the third body possibly dynamically connected with the system. Using measured radial velocities and our fit to TESS photometry, we compute best to date parameters for the components and the orbit of the binary system. In the system DR Vul we confirmed the third body and also its nature by obtaining its spectra. We present the first orbital solution available for the central binary. The triple system does not seem to follow the theoretically predicted common inclination of the orbits. 1
Multi-frequency research of symbiotic binaries
Merc, Jaroslav ; Wolf, Marek (advisor) ; Hambálek, Ľubomír (referee) ; Mikulášek, Zdeněk (referee)
Symbiotic stars are among the widest interacting binaries. They consist of a late-type, cool giant and a hot component, which is typ- ically a white dwarf or in a few cases a neutron star. The presented thesis summarizes all the relevant information on the symbiotic bi- naries, including both components of systems, their activity, and other manifestations of variability. Symbiotic systems are presented as unique astrophysical laboratories in the study of stellar evolution, mass transfer and its accretion, stellar winds, jets, and other physical processes. A part of the thesis presents the New Online Database of Sym- biotic Variables, a modern, complex, and most up-to-date catalog of these binaries that currently contains more than 1 000 objects in the Milky Way and another 16 galaxies. At the same time, the Database constitutes the most comprehensive collection of orbital, stellar, and observational parameters of all known symbiotic binaries. These data are studied in detail in order to better understand the symbiotic pop- ulation. From the Database, poorly characterized symbiotic candidates have been selected and studied on the basis of new and archival ob- servational data and information from the literature. A substantial sample of 47 symbiotic candidates from the literature and 3 newly...
The evolution of astronomical photometry
Baláž, Jáchym ; Šolc, Martin (advisor) ; Wolf, Marek (referee)
This bachelor's thesis focuses on the evolution of photometry in astronomy. It begins with the first astronomers of the classical era, follows the improvement of star atlases, before and after the discov- ery of the telescope. The thesis documents the dicovery of optical photometers, photography and photoelectric cells and the influence of these on photometry. Throughout the advancement in technology, the thesis follows the changes in astronomical photometry, from the definition of the magnitude to the introduction of colour indices. The historical excurse ends in the present time - with the use of CCD sensors and key space missions of the modern era. The thesis also focuses on the history of variable star photometry. It also lists the observatories in Czech Republic, or more precisely their instruments, with photometric research. 1
Photometric study of dwarf nova EX Dra
Pilarčík, Lukáš ; Wolf, Marek (advisor) ; Mayer, Pavel (referee)
Photometry of eclipsing dwarf-nova EX Draconis was performed at the observatory of Astronomical Institute of the Academy of Sciences of the Czech Republic in Ondřejov and at the Astronomical Observatory on Kolonické sedlo during 63 nights. I calculated times of minimum light by two methods - the mirror method and the derivative method. The mirror method is more precise for these measurements with longer exposure time and smaller coverage of the light curve of eclipse. 53 new times of minima calculated by the mirror method and times of minima obtained from the older articles about EX Dra were included in the O-C diagram and fitted by the sine function and theoretical curve of LITE caused by an unseen third body. Period of cyclic changes for the sine function is 25 years, instead of 4 or 5 years period given in older papers.Period of the third body orbit is aproximately 17 years and its minimum mass is 53.5 Jupiter's mass. The sum of squared deviations is 5 times smaller for the LITE, which means that the LITE ilustrates the O-C diagram better. I determined the average outburst period for three observational seasons and I drew the phase curve of outburst. Finally, I calculated the short period of the light changes outside eclipse.

National Repository of Grey Literature : 53 records found   1 - 10nextend  jump to record:
See also: similar author names
3 Wolf, Martin
2 Wolf, Michal
Interested in being notified about new results for this query?
Subscribe to the RSS feed.