Pravidelné semináře pořádáme jednou měsíčně (říjen–červen, zpravidla první pondělí v měsíci) od 13 hod v seminární místnosti pracoviště Ondřejov.
05. 11. 2012
Omicron Puppis: another Be + sdO binary?
Abstract: The spectrum of the Be star o Pup is shown to vary periodically with a period of 28.9 days. A
radial-velocity variable He I 6678 A emission component suggests that the star is the same type as
phi Per, 59 Cyg and FY CMa, i.e. binaries consisting of a Be star and a hot companion that
illuminates the Be star disk (also called phi Per-type binaries or Be+sdO binaries). The range of
radial-velocity variations of the stronger emission component in the helium line observed in o Pup
is about 270 km/s, a value which is in good agreement with the range derived for phi Per-type
binaries. The radial velocity curves defined by the prominent emission peak in He I 6678 A line and
H alpha + Paschen emission move in anti-phase. We suggest that o Pup is generically similar to phi
Per-type systems and may represent the fourth case of a Be star with a hot subdwarf companion.
Dále pořádáme menší semináře jednotlivých oddělení:
Semináře slunečního oddělení
Každé úterý v 13:00 (září–červen, s výjimkou úterků po celoústavním semináři) v zasedací místnosti slunečního oddělení pracoviště Ondřejov.
15/01/, 13:00On the physical meaning of the n-distributions in solar flares and soft X-ray line spectraAbstract: By analyzing X-ray spectra we detected n-distributions of electron energies in the impulsive phases of solar flares. We found that the n-distribution and moving Maxwellian one are nearly the same at their high-energy parts. Based on their mutual fitting at these parts we derived a simple relation between parameters of these distributions as: v0/vT~(3/4 n)1/2, where v0 is the drift velocity and vT is the thermal one. However, we found that observed values of the parameter n of the n-distribution correspond to very high values of the parameter v0/vT, for which the moving Maxwellian distribution is unstable. Thus to generate the distribution similar to the n-distribution, some stabilization process is necessary. Therefore, we investigated processes in the electron beam-return current system in the impulsive phase of solar flares using a 3-D electromagnetic particle-in-cell model. We found that in such a system the strong double layer (DL) can be formed and in its electric field the electrons are strongly accelerated. The high-energy part of their distribution resembles to that of the n-distribution and remains stable.Thus, a detection of the n-distributions indicates a presence of double layers in solar flares. A similarity of processes in solar flares and those in the terrestrial aurora, where the double layers were observed by FAST satellite, support this idea.
Zářivě-(magneto)hydrodynamické semináře
Zpravidla 1x za 14 dní ve čtvrtek od 11 hod (říjen–červen) v zasedací místnosti slunečního oddělení pracoviště Ondřejov.
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Semináře oddělení GPS
Zpravidla v knihovně pracoviště Praha–Spořilov v různé dny.
28. 01. 2013, 14:00Astronomical Institute, Academy of Sciences, OndrejovNews from ALMAAbstract: The Atacama Large Millimeter/submillimeter Array (ALMA) is a major new facility for world astronomy. When completed in 2013, ALMA will consist of a giant array of 12-m antennas, with baselines up to 16 km, and an additional compact array of 7-m and 12-m antennas to greatly enhance ALMA's ability to image extended targets. Construction of ALMA started in 2003. The ALMA project is an international collaboration between Europe, East Asia and North America in cooperation with the Republic of Chile.
ALMA Early Science Cycle 1 observations will start in January 2013 and span 10 months. It is anticipated that approximately 800 hours of array time will be available for Cycle 1 projects.
I will present the Czech ALMA Node activity during the previous year.(Takes place at: Sporilov library)