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A study of dynamically bounded triple systems
Švrčková, Jana ; Harmanec, Petr (advisor) ; Korčáková, Daniela (referee)
Hierarchical triple stars consist of two stars orbiting each other on a close orbit and a third, more distant star. This is the only observed dynamically stable configuration of triple systems. The third star needs to be far enough from the close binary, otherwise the stars start moving chaotically which eventually results in ejecting one of the components out of the system. This condition is described by several criteria of dynamical stability. HD 152246 is a hierarchical triple star with an eccentricity seemingly too high to be dynamically stable. Using a recently observed set of spectra, I determined more precise and accurate orbital elements of this system. I showed that the eccentricity value is lower and the system does fulfill stability criteria. I also showed that the system is dynamically evolving - the short orbit inclination is changing in time. δ Cir is a triple system that consist of an eclipsing binary and a more distant third star. Moreover, there are some signs that the third star is also a binary. Using spectra of the system, I calculated a more precise mutual period of the eclipsing binary and the third star as well as its other orbital elements. I also combined spectroscopic and photometric data to determine more precise parameters of the eclipsing binary. 1
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Study of the eclipsing binary systems showing the inclination change
Ševčíková, Klára ; Zasche, Petr (advisor) ; Harmanec, Petr (referee)
The presented thesis is focused on the study of eclipsing binaries showing inclination changes of orbital plane. This orbital precession effect is probably caused by the presence of a third body in the system. Our method is using the study of changing eclipse depth, which allows to independently estimate parameters of the inner system and also to set some constraints on the parameters of third body. In the thesis there were analysed in detail 3 eclipsing binaries using photometric data taken from MACHO and OGLE I-IV catalgoues and from DK154 telescope observations. For the system OGLE-LMC-ECL- 10338 the nodal period was around 115 years, outer body orbits inner binary probably with period <100 days and its mass is <1,38 M⊙. For the system OGLE-LMC-ECL-10413 the nodal period was around 168 years, outer body orbits probably with period <90 days and its mass is <1,50 M⊙. For the system OGLE-LMC-ECL-14394 the nodal period was around 118 years, outer body orbits probably with period <450 days and its mass is <3,12 M⊙. 1
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A study of binary stars with accretion disks
Chadima, Pavel ; Harmanec, Petr (advisor) ; Krtička, Jiří (referee) ; Mourard, Denis (referee)
This thesis contains spectroscopic analyses of two unusual binaries with circum- stellar disks - β Lyr and ǫ Aur. Several hundred optical spectra were processed and analyzed for both binaries which led to several original findings. For β Lyr, it was a discovery of a weak shell spectrum originating in a disk pseudophotosphere and a hidden satellite spectrum, present only during eclipses, which arise from additional absorption of the primary light passing through the gaseous envelope around the secondary. For ǫ Aur, it led to the discovery of the apparent multiperiodic line vari- ability occuring during the current eclipse with a dominant and common period of 66d .21 and to an explanation of complex Hα line profiles during the eclipse which is again caused by an additional absorption of a primary light in an atmosphere of a dark disk around a secondary. Also rich series of radial velocity measurements and photometric observations were collected and used to determine a new precise orbital solution for ǫ Aur. Further, a hydrodynamical and a radiative modeling of a discontinuous mass transfer in a close binary system was carried out which resulted in a formation of an elongated disk with a slow prograde revolution, demonstrated itself by double emission Hα line profiles that exhibit V/R variations.
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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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Planets by Other Suns
Hrudková, Marie ; Harmanec, Petr (advisor) ; Budaj, Ján (referee) ; Torres, Guillermo (referee)
Exploring distant planetary systems can help us to understand our own. In this thesis, two methods are further investigated for this purpose. First, to detect Earth-mass planets highaccurate measurements of radial velocities and also accurate barycentric corrections are needed. The program for computing these corrections was developed. The accuracy achieved is few cm s1 and hundredths of s for radial velocity and time corrections, respectively. The program was used to compute barycentric corrections of the 51 Peg system, for which measurements with the 2-m Alfred-Jensch Telescope were taken and analysed. Second, the method of planetary transits was used for a transit timing study of two transiting exoplanetary systems, HD 189733 and TrES-1. The data were taken with the 4.2-m William Herschel Telescope and the 2.6-m Nordic Optical Telescope, La Palma. The program using the Markov-Chain Monte Carlo simulations was written for a purpose of a transit timing study to derive system parameters, mid-transit times and their uncertainties. An additional planet in a transiting system perturbs the motion of the transiting planet, and the interval between the mid-eclipses is not constant. Deviations from the predicted mid-transit times which can reveal the presence of other bodies in the system were analysed.
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A new study of orbital and long-term variations of the Be star phi Persei
Jonák, Juraj ; Harmanec, Petr (advisor) ; Krtička, Jiří (referee)
The well-known spectroscopic binary ϕ Per is a peculiar compact system, composed of a Be star with an O-type subdwarf companion. A set of nearly 400 spectra in the red and blue regions from Ondřejov and Potsdam Observatories as well as spectra published in the BeSS database were examined. From the radial velocities of Hα, Hβ, and Hγ emission lines and FUV observations from the IUE and HST, a new precise ephemeris was determined. The revised values of M sin3 (i) are 11.84 and 1.48 M (with uncertainties of 0.64 and 0.09 M ), re- spectively, for the primary and secondary. In addition, the system shows cyclic variations (with a time scale of about 5 years) in the profiles of Balmer lines, manifested in their radial velocities, central intensities and V/R ratios. Understanding complex stellar systems requires combining multiple types of ob- servations and creating models of sufficient complexity. In our case, a combination of interferometric visibilities from the CHARA/VEGA array, spectral energy dis- tribution as well as individual spectral lines were used. Radiative-transfer compu- tations were performed with the program PYSHELLSPEC, and physical parameters of the ϕ Per primary and the surrounding disc were derived. They correspond to an evolved system, in which most of mass was transferred from the secondary to...
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