No abstract available

[en] Using a chemical model based on ion-molecule reactions in cool interstellar clouds, the deUterium enrichment of volatile material in comets is discussed. It is assumed that hydrogen containing molecules are deuterated before accretion and condensation on the core-mantle dust particles from which the cometesimals are formed. The estimated total ratio in a cometary nucleus is D/H approx. 2x10^-4. The possibility of isotope fractionation in comets means, however, that these objects are not suitable for primordial deuterium tests. On the other hand, deuterium abundance might be a sensitive indicator of the physical properties of the environment where comets are formed. (author)

[en] The occurrence of flares was statistically processed, separately for those with type II and type IV radio bursts, in relation to the sunspot groups in which these flares took place. The period in question was cycle No. 20, 1966-1976. Zurich and magnetic typification were taken into account. The results are summarized in tables and graphs. As compared with flares accompanied by type II bursts, flares with type IV display an enhanced tendency to occur in more complex active regions in which more magnetic energy is accumulated in a small space (type delta). The occurrence of flares with type II and type IV bursts in the course of cycle No. 20 shows anomalous behaviour, in particular a conspicuous decrease of occurrence from 1970 to 1971, which conforms to the behaviour of some other solar activity parameters. (author)

[en] Samples from three unmanned Soviet lunar missions, Luna 16, 20 and 24 were investigated for the concentration of cosmogenic radionuclides ²²Na and ²⁶Al and for tracks formed by nuclei of the iron group of cosmic rays in mineral grains (feldspar). The depth profiles of ²²Na and ²⁶Al are compared with theoretical predictions obtained using three independent methods of calculation of the production rates of cosmogenic radionuclides. The best fit was obtained for an intensity of galactic cosmic rays of 0.24 protons.cm^-2.s^-1.sr^-1 with R>0.5 GV for the past million years. (author)

[en] Very fast vibrations of the solar image during telescopic observations are discussed. It was found that, due to atmospheric heat turbulence, the positions of individual detailed formations in the sunspot umbra in pictures taken over an interval of 2.5 s may differ by as much as 1''. (author)

[en] The photometric and spectral history of the object since 1891 is briefly reviewed. The major outburst occurred in the year 1964 and in 1969 a strong ultraviolet and red continuum was detected along with the appearance of permitted and forbidden emission lines. After the outburst the object brightness slowly decreased but the cyclic variations with a period of 950sup(d) were clearly seen again. All photometric data thus support the suggestion that the system is an eclipsing binary. Spectroscopic data from the years 1971 to 1976 reveal periodic variations of the radial velocities of the emission lines with a period consistent with the photometric solution. The system apparently consists of a red giant of the spectral type M 5 II and of a very hot star; their masses are about 25Msub(Sun) and 1Msub(Sun), respectively. Line profiles of nebular as well as Balmer lines suggest the existence of ejected ''polar caps'' and an equatorial ring around the hot component, much like those in novae. The system can well be explained in terms of Bath's (1977) model. The hot component accretes the material from the giant via a strong stellar wind. Fluctuations in the optical brightness are probably caused by variations in the accretion rate on the hot star. The major outburst was caused by a shell flash which also ionized the expanding nebula surrounding the hot component. (author)

[en] Changes were investigated in the shape of the light curve of the close binary TX Ursae Maioris in the vicinity of the primary minimum and changes in the period were analysed. It was proved that the change in the shape of the light curve was asymmetric and the effect on determining the minimum epoch was established. The hypothesis of the existence of the effect of the rotation of the line of apsides was disproved. It was found that processes leading to a change in the period occurred at least three times. In the first approximation the values of the periods in all intervals are constant. The run of the last change indicates that it did not occur suddenly but over a period of several years. The light changes during the recent period can be expressed by a linear ephemeris derived from the photoelectric epochs of the minimum. (author)

[en] Using magnetic synoptic charts and daily maps preceding and following the development of the August 1972 proton-flare region in an extended time interval, it was shown that the evolution of such a complex solar process may be divided into more simple evolutionary phases. Each of the individual stages during the process of forming this complex magnetic situation may be compared with the phenomena observed during the growth of a normal complex of activity or even of a simple active region. These evolutionary stages are not only seen in the development of the magnetic field topology. They may be found in all kinds of solar activity and their occurrence in the chromosphere, corona and interplanetary space seems to depend on the successive penetration of the magnetic field lines into the higher layers of the Sun and its extensive atmosphere. (author)

[en] The third part is submitted of a series of papers on the coronal index of solar activity. The index is expressed in terms of the total energy emitted by the whole corona in the emission line Fe XIV, 530.3 nm. Changes in computing the index and the results for the years 1971 to 1976 are reported. (author)

[en] Dynamical friction due to both radiation and dusty cosmological background is estimated and proposed as a possible decelerating mechanism of primordial velocity fluctuations. (author)