The main results acquired and published by the research personnel of the Astronomical Institute in the year 2004 are briefly described below. Information about the reference to the published paper in the list of publications is given in brackets.

1/ The most significant results of the year 2004: Influence of the electromagnetic radiation on dynamics of the interstellar cosmic dust particles in the Solar System. Interstellar grains entering the Solar System (SS) are mainly affected by solar gravity, radiation pressure, and electromagnetic effects. The trajectories of sub-micron dust particles in the SS are also strongly influenced by Lorentz force, which, in general, influences the motion of charged dust in the magnetic field. It is usually accepted that the radiation pressure force is directed radially away from the Sun and thus reduces the solar gravitational attraction. Nevertheless, any irregularity of the particle's shape generates non-radial momentum components in the particle's frame of reference. Finally, the character of motion may significantly differ from the corresponding motion known for ideally spherical particles. The effect of particle's morphology implies relevant consequences for the evolution of the particle's trajectory and its lifetime in the SS. In contrary to the results known for spherical particles, we have shown that the charged irregularly shaped grains can be captured in a very narrow belt near the ecliptic plane and may then definitely contribute to the density increase of circumsolar dust cloud. The solar radiation force appears to be the most dominant factor affecting the capture of the interstellar grains. In addition, we found that survived non-spherical interstellar dust particles orbiting around the Sun are characterized by a quantity analogous to Kepler's third law. This fact can efficiently be utilized in various astrophysical modellings of interstellar dust particle dynamics in the circumsolar region (papers Nos. 26, 27).

2/ The most significant result obtained within frame of international collaboration: Study of the circumstellar matter and accretion discs in the interacting binary stars. Interacting binaries exhibit various forms of circumstellar matter. Accretion discs, gas streams, jets and shells galore. It is all footprinted in their spectra. Unfortunately, most of the current models treat only the binary stars and their geometry and the stars are stripped of any circumstellar matter. Consequently, properties of such a matter are not very well understood. We have succeeded in developing a computer code which is, to our knowledge, so far the only tool for interacting binaries capable of taking into account the semi-transparent circumstellar matter. The code solves the equation of radiative transfer along the line of sight in 3D moving media under the assumption of LTE. Scattered light can be taken into account assuming optically thin environment. A light curve or spectrum of the system from any angle can be calculated. The code was applied to the H alpha line originating from an accretion disc similar to that in TT Hya - an eclipsing Algol type binary. The wedge shaped disc with a Keplerian velocity field was assumed. The calculated spectral line has a shape of a double peaked emission with a central depression which is really observed. The temperature and inclination of the disc have the strongest effect on the depth of the central depression, while the outer radius of the disc, the radial density profile, and the inclination affect mainly the position and separation of the emission peaks. The overall strength of the emission is regulated mainly by the density and temperature. The era of modelling the observed emission lines in interacting binaries begins. (paper No. 12).

3/ Studies of transfer orbits between the Jupiter family comets and Encke-like orbits show that on a time scale some of the model orbits of the Jupiter family comets will change to the Encke-like orbits. This time scale is comparable to the activity period of short-period comets. The main factors for this orbital change are resonances and non-gravitational forces (paper No. 33).

4/ Using the newly published method by Lynch, we evaluated the statistical significance of the correlation between the observed sequence of mean heliocentric planetary distances and a power law. It turns out that the observed agreement very probably occurred by chance for 8 known planetary distances (Mercury to Neptune) with the added mean distance of the asteroids. However, the clearly opposite conclusion is true, if the distance of the Earth is omitted in the above mentioned sequence. It indicates a peculiar location of the Earth's orbit. (paper No. 29).

5/ There were carried out and analysed common forward scatter meteor observations of the Leonids 1996-2002 and Quadrantids 1997-2004 performed along two baselines: Lecce-Bologna and Bologna-Modra. The observations have convincingly demonstrated a filamentary structure and systematic change of the mass distribution exponent in the streams. The strongest maximum of larger meteoroids in the Quadrantid meteoroid stream was observed in 1997 (papers Nos. 34 a 37).

6/ We solved a problem of the dynamical stability of extra-solar planets in two stars systems with the theory of the general three-body problem. We used the Hamiltonian neglecting short-period terms, using von Zeipel's method. A designed analytical method properly describes the movement of extra-solar planets and gives us comparable results with numerical integration of orbital equations. This theory was applied on double star systems Gliese 86, $\gamma$ Cephei and 61 Cygni (paper No. 48).

7/ To determine the radial structure and population of the Oort cloud, the perturbation of the cometary orbits in this reservoir by the Galactic tide was analysed. Within the work, the theoretical frequency of cometary passages through the zone of visibility (ZV) was found. It was assumed that the distribution of the cometary perihelion distance in the ZV is (i) flat and (ii) linear (paper No. 30).

8/ 70 positions of comets and 480 positions of minor planets have been observed and reduced within the project of the determination of astrometric positions of selected comets and asteroids (papers Nos. 49, 75, and 76).

9/ By the analysis of the Fermo meteorite (Italy) the non-analyzed chracteristics of this meteorite were derived and were compared with other known chondrites.

(paper No.63).

10/ Using data from the IAU Meteor Data Center it was shown that the rate of interstellar meteoroids is in catalogues of MDC overestimated by more than of one order of magnitude for photographic, as well as for radio meteors. (papers Nos. 59 and 60).

11/ A degree of condensation of a cometary image was analysed form the point of view of an instrumental factores influence on scales of cometary magnitudes. Qualitative definitions of individual steps of the DC-scale with low precision were replaced by a new quantitative formula (paper No. 73).

12/ We have studied a particular type of Cremonian space-time giving rise to a scenario where the signature of the very early Universe might have been different from that currently observed. (paper No. 42).

13/ It was conjectured that the question of the existence of projective planes whose order is not a power of a prime is intimately related with the problem whether there exists a complete set of mutually unbiased bases in an n-dimensional Hilbert space if "n" differs from a power of a prime (paper No. 41).

14/ The green corona intensities (530.3 nm), expressed in the coronal index of solar activity (CI) have been studied in the period 1939-2001. There was found an 11-year cycle periodicity in the CI; however, the disagreenment occurs beetwen the CI and sunspot number for some cycles. Subsidiary rotational rates of 25 and 33-days have been detected in the CI using the Fourier Transform Technique. The main rotational rate of the CI is of 27.3-days (paper No. 38).

15/ Analysis of the scatterd light in the Earth's atmosphere (called 'aureola'), acquired together with the green coronal intensity (530.3 nm) observations obtained at Lomnicky Stit since 1965, has shown that the aureola intensities do not vary with the solar cycle as it was generally accepted. (paper No. 40).

16/ A comparison of daily values of coronal holes (CH) in the green 530.3 nm coronal line intensity, as derived from the green coronal homegenous data series (HDS), with daily means of cosmic ray (CR) intensity during the 1953-2002 period shows a very good correlation of the CH and CR variations. The time shift between the CH and CR is 200 - 270 days with a maxima at 230 days. This indicates the potential for a possibility of using coronal emission data as one of the parameters for an eventual prediction of the level of cosmic ray flux at neutron monitor energies (paper No. 28).

17/ Evidence for the shocks waves, originating at the edges of the granules in the solar photosphere, was derived by an analysis of the spectroscopic observations of the solar granulation. For the first time evolution of this event and its relation to the concentration of the magnetic flux in the intergranular lane was documented. Comparison of the observational signatures of the shock wave in the spectral line profile of the ionised atom of iron with the results of the numerical magnetohydrodynamical modelling of the solar photosphere leads to an important agreement, which confirms results of the numerical simulations of convection on the surface of the Sun (paper No. 39).

18/ Basic vertical structure of the atmosphere of the UZ Lib primary was derived as based on spectroscopy from the season 1996-2000. The primary is a red giant with a high vsini value and possessing spots in its atmosphere. The secondary has significantly lower brightness. The study is based on static 1D spherical models applied to the hydrogen alpha profiles. The results for the primary component's atmosphere are the following: the photosphere, chromosphere and outer corona in agreement with solar analogy and sporadic energy flares and complex velocity fields. (paper No. 54).

19/ A long-term orbital period increase of the contact binary AK Her in 1892-2003 was explained either by a mass transfer between the components or by a light-time effect due to the presence of another body in the system. The 57-year modulation of this increase was caused by the presence of the third body with the mass of 0.22 solar masses. The 17.7-year variation of the orbital period was explained by cyclic changes of the presence of spots on the surface of this contact binary. (paper No. 10).

20/ Analysis of the long-term photometry of the symbiotic nova HM Sge obtained in 1975-2003 revealed that the maximum of brightness caused by the outburst in august 1975 was followed by two brightness minima with the duration of 750 and 2100 days. The second minimum was visible only in the U band. The minima were explained by the eclipses of the hot component and the hot shocked region formed by colliding winds of the components by a Mira type giant. (paper No. 23).

21/ Long-term photometry of the classical nova V723 Cas and symbiotic novae V1329 Cyg, PU Vul, V1016 Cyg and HM Sge was used to find their orbital periods. The arguments in favor of the presence of the third components in these systems and physical processes, responsible for brightness variations, were suggested. (paper No. 24).

22/ A third body in the semi-detached eclipsing binary star UX Her was detected from the observed minima behavior. The orbital elements and the minimum mass of the third body were determined. (paper No. 51).

23/ Photometric observations of 15 symbiotic stars, carried out mostly at the Skalnate Pleso and Stara Lesna observatories, showed unexpected variations in their light curves: outbursts, wave-like variations and effects due to eclipses. (paper No. 46).

24/ The effect of emission lines in the spectra of symbiotic stars and novae during their nebular phases was investigated. For the symbiotic nova V1016 Cyg it was found that 68, 78 and 66 percent of the observed flux in the U, B and V filters is radiated by emission lines. (paper No. 43).

25/ The nature of periodic variations in the star's brightness as a function of the orbital motion of binary components was discussed and the effect of apparent changes of orbital periods was described within photometric investigation of symbiotic stars. (paper No. 44).

26/ A model of spectral energy distribution in the ultraviolet, optical and infrared spectral region of the symbiotic stars BF Cyg and AG Dra during their phases of activity identified two types of outbursts. (paper No. 45).

27/ UBVRI CCD photometry of the symbiotic nova V1329 Cygni, obtained using 50cm telescope at Stara Lesna, revealed a sudden brightening of the object in August 2004. The flare has a largest amplitude in the U passband (0.41 mag). It is the first recorded flare of the object after the main outburst. The object reached quiescence brightness in about 3 months. (paper No. 71).

28/ Comparison of the observations of the eclipsing binary V685 Cen from the ASAS database and observations published by van Houten et al. (2003) clearly showed the difference in the minima depth. This observational fact was interpreted by the precession of the orbit of the eclipsing binary induced by a third component on a relatively close orbit. The rate of the precession indicates that the orbital period of the third component is shorter than one year and the precession period is several hundred years. Assumption of the third light markedly improved the light-curve solution. (paper No. 67).

29/ The light curves of the systems YY CrB and EQ Tau were analysed by the ROCHE code which was created by Dr. Pribulla. The light curve of the YY CrB is the first one observed from the Earth. After analysis of the light curves we obtained photometric elemets. In combination with published spectroscopic elements, we determined the absolute parameters of the systems. Having these results we created 3D models of the systems and discussed their evolutionary status. (paper No. 52).

30/ The new eclipsing symbiotic system YY Her was discovered and the secondary minimum was observed in detail. On the basis of CCD photometry in BVRI colours the increased photometric activity with consecutive outburst was detected in the system. The energy balance and time scales of particular events have been calculated. The observational material was obtained at the observatories in the frame of international photometric campaign in the Czech Republic and Slovakia (papers Nos. 21 and 22).

31/ The CCD photometric and spectroscopic observations of Nova Aql 1999 (V1493 Aql) were analysed. The orbital period of the system with the value of 3.7 hours, extremely large distance of the nova 34.4 $\pm$ 6.2 kpc and expansion velocity of the envelope 1660$\pm$60 km/s was derived. (paper No. 16).

32/ Photometric and spectroscopic observations of HD 6226 led to a conclusion that it is a newly discovered bright Be star. The brightness and emission lines variability are well correlated. Based on the types of the observed variabilities the star was classified as a Be star of Gamma CMa type. (paper No. 11).

33/ High resolution spectra of the extreme helium subdwarf BD+254655 from the 6m SAO telescope were analysed using the NLTE model atmospheres. Basic parameters of the star were derived. (paper No. 13).

34/ Zeeman spectra of the double-lined double star HR6611 with Am components were analyzed. Previously in the literature suggested presence of magnetic field was not confirmed. (paper No. 82).

35/ Observed variations of metalic lines profiles in the H-alpha region of the roAp star HR3831 correspond to a non-uniform distribution of the elements over the surface of the rotating star. (paper No. 55).

36/ Secondary spectrum in the SB1 system HD861 was discovered. The secondary is a much fainter and cooler star, with a much lower rotation velocity than the primary star. This enabled us to estimate a preliminary mass ratio of about 2:1. (paper No. 57).

Jan Rybak 2005-04-29