Models of stellar atmospheres are based on assumption of their plane-parallel or spherical symmetry. Violation of this assumption by tides and rotation in close binaries leads to incompatibility of hydrostatic and radiative equilibria. Improvement of model atmospheres in this respect is desirable for simulation of light curves and line profile changes. Moreover, atmospheres of
contact components of interacting binaries determine initiai conditions of dynamics of gaseous streams and in this way influence the behaviour of the binary system.
The properties of the standard accretion disk are summarized. Recent models of steady and time dependent disks are discussed. The two dimensional calculations of accretion flows are examined.
Models of the variations and distribution of the upper atmosphere density are constructed, using modelled as well as observed data. Theoretical expression of the model is used in the equations of motion to study the drag effects of the atmosphere.
The present study deals with the properties oi the Šolc type monochromatic interference-polarization filters and the possibilities of their use for solar observations. In the first part the characteristics of the Šolc filter in distinction to those of the Lyot filter are mentioned. Then, the features of some of the working Šolc type filters are studied and the results obtained by means of them are compared with the theoretically assessed values. In particular the following properties háve been investigated: the half-widths of the
individual filters and their dependence on the wavelength, the spacing of the principal maxima of the filters and their dependence on the wavelength, the spacing and intensity of the first secondary maxima, the permissible convergence of the beam of rays entering
into the filter, the dependence of the position of the maxima on the inclination of the filter to the optic axis, the dependence of the position of the maxima on temperature and the transmission of the filter. The obtained results are presented in table and diagrams.
Summarilly it can be said that the Šolc type filters offer an advantageous research tool in cases, where their considerable intensity of the secondary maxima and their high sensitivity to the convergence of the beams is not a handicap, in other words, that they are very well suited for observations of prominences in a coronograph, where their high transmission at a relatively large half-width will be appreciated. On the other hand, in cases where a smáli half-width is required, that is, first of all in observations of the
chromosphere, the use of the filters has some limitations. In the concluding part some actual cases of application of the mentioned filters for observations of prominences and of the chromosphere are demonstrated.
Sources of maser radio emission in the water vapour spectral line at 1.35 cm are considered, which are situated in star formation regions, in tho vicinity of young stellar objects. The H2O emission of many maser sources in subject to strong variability; maser activity is thereby of a cyclic character with a period of a few years. On the basis of observational data, it is aassumed that the region of maser generation is located in a rotating gas-dust disc around a young stellar object. The author auggests three models explaining the masers´ cyclic non-stationarity.
(1) The maser´s variability is connected with the variable luminosity of the central stellar object, due to non-stationary accretion onto it.
(2) In the central cavity of a large circumstellar disc containing the H2O maser, a smaller disc is located, with its axis tilted to that of the larger disc. The stellar wind jet collimated by the small disc and flowing out from its poles impacts connecutively onto different parts of the large disc´s internal surface. This results in the time- and space-variable maser pump.
(3) If the maser is unsaturated and amplifies the background continuum radiation, then strong maser flares may be connected with radio flares of the centra! object (due, e.g., to its magnetic activity) and the corresponding increase of the maser´s input intensity.
Oboervational tests for the suggested models are discussed.
One of the best-known Czech scientists, theoretical astronomer Prof. Jan Palouš, a member of the Academy Council of the ASCR, continues his discourse in part two of an interview about differences between astronomy of the 19th and the 21 centuries, computer simulation of Space, about striking fact that the Sun is not a binary-star and the finiteness of Space. / and Marina Hužvárová.
A conference honored the late Prof. Zdeněk Švestka, one of the great defining personalities of twentieth-century solar physics. His main scientific interest focused on solar flares. During his year at Ondřejov, he became an expert in flare spectra. Later his interests extended into white-light flares, proton flares, and their radio signatures (type II and IV bursts), which were suggestive of shock-acceleration of particles. The conference, organized by the Astronomical Institute, took place on 23-27 June 2014 in Prague. Zdeněk Švestka, born on 30 September 1925 in Prague, passed away on 2 April 2013 in Bunschoten. and Petr Heinzel,Marian Karlický, František Fárník.
The time evolutlon of the metalliclty wlthln the Galaxy has been analysed on the base of published data for star clusters. The resulting age-metalliclty relation seems to split into two independent paths, passing the same age range over 10^10 years. The lower relationship resembles that for the Magellanic Clouds. Such a picture of the chemical evolutlon of the galactic matter is consistent wlth the observed division of the considered sample of open clusters into two groups differing in metallicity and spatial distribution, similarly to the division found for globular clusters. The metal-poor open clusters resemble metal-rich globulars. This can suggest that our galaxy has evolved from spherical metal-poor configuration represented in the considered sample of star clusters by metal-poor globulars, through a thick dlsk phase wlth the middle metallicity up to thin metal-rich disk wlth its representative
metal-rich open clusters. The transition between each of the above phases was more or less abrupt in its characteristic chemical and spatial properties.