Přednášky a semináře
Semináře pořádáme se zrhuba čtvrtletní periodou v půldenním bloku.
Constraint on AGN corona size with fully relativistic modelling of 3D corona
The “lamp-post” scenario was usually used to describe AGN corona, in which the corona is assumed to be an infinitesimal point source on the symmetry axis. In some AGNs, especially NLS1s, the broad iron line profile requires extremely compact corona. On the other hand, the corona must be large enough to intercept enough seed photons to be able to produce the observed X-ray continuum and reflection spectrum. One attempt to constrain AGN corona size was made by Dovciak & Done 2016, in which the corona size was estimated by conservation of photons during Comptonization process. They found out that for one NLS1 1H 0707-495, the size of the corona must be substantially larger than 1 GM/c2. In that work, the Comptonized spectrum was evaluated assuming lamp-post geometry and the corona size was estimated under the assumption that the emission of the corona is homogeneous. To calculate the spectrum of 3D corona (i.e., the corona is extended and with finite height) self-consistently, we perform a fully relativistic Monte Carlo calculation of energy and polarization spectrum of AGNs of disk-corona geometry, taking into account propagation of null geodesic in Kerr space-time and Compton scattering process.
Age estimation of asteroid pairs and clusters
We will briefly present a method for identification of young (age ≲ 2 Myr) genetically related asteroids and estimation of the time of their separation. Assuming a gentle break up event (e.g., by rotational fission), the studied paired or clustered asteroids had very low relative velocities at the time of separation, on an order of 1 m/s, and their distances in the space of mean orbital elements are still rather low at present. For selected candidates we performed backwards integrations of their geometric and Yarkovsky clones and we were searching for close and slow encounters between them. In the end we will overview several interesting results.
Solar Patrol Service of Ondřejov Observatory, Astronomical Institute CAS
There is a long tradition of the Solar Patrol Service at the Ondřejov Observatory for more than 40 years. This service daily produces solar astronomical data like sunspot drawings, white light and H-alpha images, depending just on weather and technical conditions. Since 1978, solar activity forecast is issued weekly and distributed to international solar databases and several public institutions within the Czech Republic. Recently also the daily forecasts were established, which are now broadcasted by the national radios and TVs. The huge data archive contains over 80 years of photospheric or chromospheric observations. Nowadays the older data are digitised to build a fully digital version of archive. The long term data-sets can be used for studies of solar variability.
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.
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