Seminars

29.4.2021, 13:30 – online MSTeams
P. Gajdoš: Stability of the orbits in exoplanetary systems with more components.
Abstract:The main topics of this seminar are planetary dynamics and resonances among planets in extrasolar systems. We studied six extrasolar systems with transiting exoplanets in more detail. We observed significant variations in the transit times of the exoplanet Kepler-410 Ab. We determined the most probable generator of the observed variations – an additional planet with a mass of 1.8 M_Mars located near the 3:2 orbital resonance. We did not detect any serious transit timing variations for the hot Jupiters WASP-92 b, WASP-93 b and WASP-118 b. Therefore, we focused on searching for stable orbits in these systems where other, yet undiscovered exoplanets could exist. We also studied the dynamics of triple-planetary systems Kepler-18 and Kepler-23 which look to be very similar but their dynamics is completely different. We observed periodic changes of times of transits and the libration of the resonant angle which belongs to the mean-motion resonance 2:1 between a pair of planets Kepler-18 c and d. However, the Kepler-23 system started to be chaotic very early in our simulations. The source of instability is the couple of planets Kepler-23 c and d which are in the orbital resonance 7:5.

15.4.2021, 13:30 – online MSTeams
M. Čokina: Light Curves Modeling of Eclipsing Binary Stars
Abstract:In the work we present a couple of methods intended for the triangulation of stellar surfaces in the problem of light curves modeling of binary star systems. The main goal was to describe the stellar surface and stellar spots by a triangle mesh. We implemented a three-dimensional Delaunay triangulation as one of the methods to triangulate point cloud, which is obtained as a Roche model solution. The thesis also presents new methods of triangulation of smooth concave objects, represented by over-contact binaries. In the first case, we used two-dimensional Delaunay triangulation in the local state of three-dimensional space. The second elaborated method is based on transforming a concave object to a convex object and triangulated by standard Delaunay three-dimensional triangulation. An enhanced triangulation method was implemented in brand new binary stars light curves modeling and analyses software ELISa. The basic physic used in ELISa is based on enhanced, commonly used approaches that are based on Wilson legacy (Wilson, 1979). ELISa attempts to be a competitor to the well-known software PHOEBE2. The development was focused on balance in runtime speed and precision. These demands were measured with a positive result. Built-in functionality is an analytic module with the capability of fitting curves of radial velocities as well as light curves. Two different methods were implemented for such purpose, first based on the non-linear least-squares method and second based on nowadays popular Markov chain Monte Carlo method. These methods and examples of their results are presented as well.

28.3.2019, 13:30 – room SJ1S24
M. Fedurco: Modelling of eclipsing binaries with pulsating components
Abstract:In recent years, data from photometric surveys and space based telescopes provided us with data of unprecedented quality that are extremely valuable in research on low amplitude pulsations. Recent research shows that a large number of the pulsators are members of eclipsing binaries. Presence of eclipsing binary features in the light curve such as eclipses, reflection effect and ellipsoidal variation usually overwhelms the light curve variations caused by pulsations. Therefore, there is a need for comprehensive model of eclipsing binaries with pulsating components that will be able to help to disentangle the binary and pulsator contribution to the overall light curve and also it will enable to model a behavior of pulsation modes during partial eclipses of the pulsator. We decided to develop and implement such model in interpreted, high-level, general-purpose programming language Python in order to achieve easy usability and modularity.

28.3.2019, 13:30 – room SJ1S24
P. Gajdoš: Variations of transit times of exoplanet Kepler-410 Ab.
Abstract: This presentation is focused on the study of the resonance perturbation between exoplanets in the multi-planetary systems. The main used tools were numerical simulations and solving the n-bodies problem. I detailly studied the Kepler-410 system where the significant transit-timing variations were observed. Using the radial-velocity measurements from Slovak and Czech observatories, I rejected the hypothesis that these variations are caused by the presence of another stellar body in the system. Working with different numerical simulations, I found out the most probable generator of the observed variations. It is an additional planet with a mass of 1.5 mass of Mars orbiting near the resonance 2:3 with the known transiting planet Kepler-410 Ab. The confirmation of this planet is hardly possible at the present time.