Přednášky a semináře
Semináře pořádáme se zrhuba čtvrtletní periodou v půldenním bloku.
The Renchen meteorite fall – recovery of meteorites exactly according to our prediction
Instrumental observations of fireballs, especially those that can produce meteorites, are of great scientific interest and importance because meteorites provide us with a surviving physical record of the formation of our solar system and a direct link to their parent asteroids. Last such rare event occurred over the most western part of Germany around the middle Rhine near the borders of Germany and France on July 10, 2018 shortly before half past eleven local time (CEST). In spite of a quite bad weather over whole Central Europe this bolide was recorded by instruments of the Czech and German parts of the European Fireball Network, from sites where it was at least partly clear at the time of its passage. Thanks to these records, this bolide could be reliably and accurately described. Among others, we were able to predict that it ended with a multiple meteorite fall and determine the area where meteorites fell and how large they should be. The great success is that shortly after sending the information about the impact area to the German colleagues, the meteorites were recovered by a German searching team exactly in the predicted locations for given meteorite mass. This event therefore fall into the rare category of meteorites “with pedigree”, i.e. meteorites with known trajectory and pre-impact heliocentric orbit. The basic results based on the analysis of the available records will be presented. Recovery of meteorites and their analysis will be also mentioned.
Sparsity regularization and 3D NLTE inversion problem
In the last decade, we have witnessed a great progress in the mathematical theory of sparsity regularization. The breakthrough discoveries in this and related fields led to many important applications in science and technology (compressed sensing, matrix completion, computer tomography, geosciences, deep learning, ...). I will show how the concept of sparsity regularization can be used to solve, for the first time, the notoriously difficult 3D NLTE inversion problem.
Truncation of AGN jets by their interaction with stellar clusters
We study the effects of interaction of jets in Active Galactic Nuclei when they encounter various obstacles, namely, stars in Nuclear Star Cluster surrounding the nucleus and passing across the inner jet. The interaction provides a scenario to address non–thermal processes and jet mass loading. In jet–star interactions a double bow–shock structure is formed where particles get accelerated via diffusive mechanism. Individual encounters have a limited effect, however, dense clusters of massive stars can truncate the jet as the cluster crosses the jet line near the jet launching region. Much of the jet kinetic energy density is transferred to the shock and it becomes available to accelerate particles. We conclude that the interaction of jets with clusters of massive stars is a promising way to explain detectable levels of gamma rays from Fanaroff–Riley class I of edge–brightened radio galaxies.
A New Observing Instrument For Transient Phenomena in Ondřejov: The Small Binocular Telescope
There is a new observational device in Ondřejov - a double 20 cm wide field camera, designed primarily to search for transient astrophysical phenomena as supernovae, GRB afterglows, flare stars etc., and to permit local (i.e. within Ondřejov) triggering of other telescopes. I will show the motivation for this work and discuss various scientific cases.
Archiv minulých seminářů
Dále se konají menší tématické semináře jednotlivých oddělení:
Semináře slunečního oddělení
Vždy v úterý ve 13:00 (září–červen, s výjimkou úterků po celoústavním semináři) v zasedací místnosti slunečního oddělení pracoviště Ondřejov.
Semináře oddělení GPS
Obvykle v pondělí od 14 hod v přednáškové místnosti pracoviště Praha–Spořilov.
(informace nejsou k dispozici)