Results

The main results published by the staff of the Astronomical Institute in the year 2003 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 2003: Spectral energy distribution in symbiotic binaries. We have elaborated a quantitative model of the spectral energy distribution for symbiotic binaries. Application of this model to the ultraviolet spectra of the prototypical symbiotic star Z Andromedae confirmed the eclipse effect independently discovered by observations from the Skalnate Pleso and Stará Lesná. Tests of the hot radiaton from the active system AR Pavonis by our model showed the presence of an accretion disk in the system embedded in an extended very hot corona. Reconstruction of the ultraviolet to infrared continuum identified basic source of the energy as an accretion process at a onto a non-degenerate star. This method represents a powerful tool, which allows us to understand better the nature of outbursts in symbiotic stars (papers Nos. 12, 35, 36).

2/ The most significant results obtained within frame of international collaboration: Search for abundance anomalies in Am stars driven by tidal interactions. It is suggested that if the tidally induced meridional circulation existed in binary star systems it might successfully compete with diffusion processes and rotationally induced meridional circulation. This could affect the chemical composition of an Am binary component. We started a systematic abundance analysis of a sample of Am binaries in order to search for possible observable abundance anomalies driven by tidal interaction in these binary systems. First three stars (HD 33254, HD 178449 and HD 198391) were analysed. Basic stellar properties, atmospheric parameters and abundance patterns were derived. We dicovered a new spectroscopic Ab component of HD 178449 (paper No. 15).

3/ Observations of ten solar eclipses (1973-1999) enabled us to describe mutual relations between the white-light corona structures and the coronal magnetic field strength and topology. The found correspondence strongly suggests a governing role of the field in the evolution of all the coronal features. Therefore, the white-light corona structures as observed over a long period of time can provide valuable information about the physical properties and cyclic variations of the Sun's magnetic field in the epoch long before introducing the direct photospheric magnetic field measurements (paper No. 39).

4/ Space-time distribution and mutual correlations among the north/south (N/S) asymmetry in various indices of solar activity have shown that the changes in the N/S asymmetry are consonant in all the activity indices considered. Quasi-biennial variations of the asymmetry index were found. A conclusion is drawn that the N/S asymmetry represents a specifically independent and very promising tool for analysis of variability in different manifestations of the solar activity (papers Nos. 66, 95).

5/ Simultaneous observations of the green corona (530.3 nm) at Norikura (Japan) and Lomnicky stit coronal station (Slovakia) with a 40-cm and 20-cm lens coronagraph has been used to study 5 min oscillations in the intensity of this line. Analysis of observational data, obtained at different places in the world at the same time, has shown reality if 5 min oscillations in the intensity that occur at special regions in the emission solar corona (not anywhere). We have already confirmed both the 47 second and 10 min oscillations in the green coronal line, observed to the present aboard space probe SOHO in the UV region. Some coronal intensity oscillations have been already observed before, however, it was assumed that they are caused with the earth atmosphere fluctuations. Oscillations in the solar corona are supposed to be as a possible source of the corona heating. For the first time we have detected tangential motions in the green coronal line structures with a speed up to 400 km/s (paper No. 27).

6/ Homogenous data of the green coronal 530.3 nm line intensity was updated for the period 1997 - 2002, and the coronal index of solar activity was derived for this period. The green coronal intensity in cycle 23 is about one third lower with the comparison of the green corona intensity in cycle 22, and this green corona intensity decrease is in agreement with the solar magnetic field intensity. The green corona maximum occurred in 2001, and coincided with the 2800 MHz solar radio flux, both 2 years shifted of sunspot number that occurred in 1999 (paper No. 33).

7/ Analysis of the time-latitudinal distribution of the green corona (530.3 nm) local intensity maxima in the period 1939 - 2002 shows regularly poleward migration that begins in mid-latitudes in cycle minina, and reaches solar poles around cycle maxima. Separation of the poleward migration branches (the north and south) has its stable time, and using this relation we forecasted forthcoming minima and maxima of solar cycles to 2050 (paper No. 87).

8/ The dependence been estimated between the both ground based time-latitudinal green 530.3 nm coronal intensity distribution and the UV corona rotational residuals as obtained by the SOHO EIT instrument (paper No. 79).

9/ Analyse of the semiempirical model of the solar granule evolution showed, that the range of photosphere, for which is possible to determine the line-of-sight-velocity, varies in time as a consequence of the evolution of the granule. This range is separated on two parts occupying lower and upper photosphere (paper No. 22).

10/ Statistics and model analysis of high resolution spectra of the solar active photosphere and chromosphere (subflare) have shown that the activity is remarkable in both layers. We found six times higher intensity of the central part of the Ca II K line in the active region comparing to the quiet one. The energy diffusion to the photosphere is straight-lined while the flow of matter follows the magnetic field-lines trajectories (papers Nos. 13, 24).

11/ For the first time shock wave was observationally documented to take place on boundary between the solar photospheric granulum and the neighbouring interganular space (paper No. 53).

12/ Study of temporal variability of the solar flare index over the epoch of almost 4 solar cycles revealed significant variability of the intermediate periods on the northern as well as on the southern solar hemisphere. Utilization of the wavelet transform allowed to determine wich periods are just harminics of the real periods of the flare index (paper No. 31).

13/ A catalogue of 361 contact binaries from all available sources was compiled. The catalogue contains new ephemerides, maximum and minimum brightness and equatorial coordinates of all systems. If available, the photometric and spectroscopic elements, parallaxes and magnitude of the O'Connell effect are also given. Selected statistical relations between the parameters and period changes of individual systems were discussed (paper No. 32).

14/ First ground-based BV observations of variable star HH UMa were obtained during the test of the new 50cm telescope at Stara Lesna. The type of the variability was not given in the Hipparcos catalogue. New, high-precision CCD photometry revealed that HH UMa is a contact-binary star. The paper gives new ephemeris of the system (paper No. 58).

15/ The first photoelectric light curves (in the Walraven VBLUW filters) of the B spectral type southern eclipsing binaries: GW Car, V685 Cen, V742 Cen and V764 Sco, obtained in the South Africa in the years 1969-1978, were presented. The light curves analysis led to the determination of photometric elements and classification of the binaries. While GW Car is almost semidetached system, other three binaries are detached systems (paper No. 15).

16/ Photometric observations of the prototypical symbiotic star Z And made at the Skalnate Pleso and Stara Lesna observatories revealed the eclipse effect in the system. A high inclination of the orbit was independently confirmed by a quantitative modeling of the spectral energy distribution of symbiotic stars (paper No. 35).

17/ A test of the radiation from the active system AR Pavonis showed the presence of an accretion disk in the system embedded by an extended hot corona. A reconstruction of the UV to IR continuum identified an accretion process at a high accretion rate onto a non-degenerate star as the basic source of the energy. This configuration solves a problem of the eclipse profile as a function of wavelength (paper No. 36).

18/ In a review on investigation of symbiotic stars a process of ionization in these systems has been discussed. By modeling the energy distribution during quiescent phases of symbiotic stars we found that total emission from the nebula agrees with that of a simple ionization model and it is responsible for the observed periodic variation in the light curves, which led to a different view on the nature of the symbiotic phenomenon (paper No. 12).

19/ It is suggested that if the tidally induced meridional circulation of Tassoul & Tassoul existed in binary stars it might successfully compete with diffusion processes and rotationally induced meridional circulation. This could affect the chemical composition of an Am binary component. We started a systematic abundance analysis of a sample of Am binaries in order to search for possible observable abundance anomalies driven by tidal interaction in these binary systems. First three stars (HD33254, HD178449 and HD198391) were analysed. Basic stellar properties, atmospheric parameters and abundance patterns were derived. We discovered the new spectroscopic Ab component of HD178449 (paper No. 15).

20/ New ephemeris was determined for the cool CP star HD188041 based on all the available photometric, spectroscopic and magnetic observations. The new value of the rotational period is the same for all the three mentioned kinds of variability, what enables to exclude all earlier published values the rotational period of the star (paper No. 26).

21/ A detailed analysis of spectra of the unique roAp star HD 101065 (Przybylski's star) near the resonance doublet Li I 6708 A was perfomed, using a most complete line list including all possible transitions between REE levels of the NIST database. We proved that the Li line components are present in the range 6707.72-6708.02 A. The overabundance of lithium amounts to 3.1 dex, the isotopic ratio $\rm ^{6}Li/^{7}Li$ is 0.3 (paper No. 34).

22/ We reconstructed the complex magnetic field in the Ap star HD 187474 within the frame of the point field source model, where virtual magnetic charges are distributed in the stellar body. The best-fit model describes sufficiently well the observed nonsinusoidal variability of the mean magnetic field modulus and the sinusoidal behaviour of the mean longitudinal magnetic field with the phase of stellar rotation. It was shown that in HD 187474 the magnetic dipole is displaced from centre of the star by 0.055 $R_{\star}$. The dipole has a size $\sim$0.035 $R_{\star}$. The angle between the stellar rotational axis and the magnetic dipole is $\beta=37\hbox{$^\circ$ }$ (paper No. 19).

23/ The study on systems SV Cam, HU Vir, AG Dor, AR Lac and YZ Cmi revealed the spot sigantures located at medium and high latitudes. The spot are typically cooler than surrounding photosphere and the locations are probably in an agreement with theoretical studies on magnetic flux-tubes. At least two independent method were used to study the spot properties. The chromosphere activity level was estimated on SB2 systems AR Lac, KT Peg and KZ And as based on hydrogen alpha spectral line profile (papers Nos. 41, 42).

24/ The deepest ever in the atmosphere photographed fireball, which terminated at a height of 13.5 km, was recorded by all-sky fireball cameras on November 17, 2001. The calculated place of the fall of meteorites from this fireball (of a total weight of 400 kg) is in Ukraine, only about 15 km from Slovakia. The orbit of the meteoroid is asteroidal one, with aphelion of 1.97 AU. The decisive photographic observation for the calculation of the orbit and the place of the fall of meteorites was obtained at the Skalnate Pleso Observatory (paper No. 92).

25/ The meteorite Fermo who fell on September 25, 1996 in Italy, was analysed in a cooperation with the Geophysical Institute Slocak Academy of Sciences from the viewpoint of its possible remanent magnetism. A simplified model describing a spread of the temperature inside the meteoroid during its flight through the atmosphere was suggested and calculated (paper No. 18).

26/ The latest version of the photographic catalogue of meteor orbits of the IAU meteor database was analysed from the viewpoint of a search for members of the Taurid meteor complex. 240 members of the complex were found and the mean orbit and radiant ephemeris for the both branches of the complex members were calculated (paper No. 86).

27/ The meteor shower of the Leonids 2002 was observed as by a forward scatter radio system so visually at the Modra Observatory. The both theoretically proposed maxima corresponding to the meteor filaments released from the parent comet 7 and 4 orbital revolutions ago were identified. The zenithal hourly rate of the Leonids at the peak of activity with a number of 3280 meteors per hour reached an activity of a meteor storm (paper No. 56).

28/ The investigation of long-term orbital evolution of asteroids with high inclination and SOHO comets model near-parabolic orbits showed that some of these bodies under the influence of the planetary perturbations return periodically to the inner part of the solar system. They cross orbits of the inner planets, among them the Earth's orbit too. The orbital stability of extrasolar planets were investigated (papers Nos. 84 a 91).

29/ Summarizing the measurements of the size of both long-period and shor-period individual cometary nuclei, a new average size of those was determined: 8.9 km for the long-period and 2.3 km for the short-period cometary nucleus. Using these values, new average masses were inferred. (paper No. 28).

30/ It was demonstrated that the cometary population in the Oort cloud can be about one to two orders lower that estimated before. It was found that the observed distribution of the reciprocal semi-major axes of long-period comets in orbits perturbed by Jupiter can be explained, when there is assumed that 8-12% observed cometary nuclei split at every revolution around the Sun. (papers Nos. 47, 71)

31/ On the base of own visual observations and the most extensive accessible observation series (IMO and Olivier) the curves of diurnal and annual variation of sporadic meteors were found. Some anomalies in obtained diurnal and annual variations were explained by insufficient separation of known shower meteors (paper No. 48).

32/ Possibilities of a conversion of extensive sets of visual observations to a uniform scale were analysed and discussed. The computer photometric catalogue consisting of 10 000 estimations for 67 long-period comets (http://www.ta3.sk/$\tilde{}$astrsven) is used as the input source (paper No. 61).

33/ We developed the method based on evaluation of lidar backscattered signal, which enables to identify contaminants in the Earth's atmosphere. Retrieval of size distribution of icy particles in noctilucent clouds was analysed using Rayleigh-Gans approximation (papers Nos. 51 and 52).

34/ The filamentary structure of the Comet Halley meteor stream has been precised from over 100 years of observations, including series from long-base (Lecce-Bologna-Modra) observations (paper No. 69).

35/ We derived mass functions for possible interstellar particles together with their changes along mass scale in 20-orders range (paper No. 70).

36/ The conditions of the interstellar dust capture in the Solar System were formulated theoretically (paper No. 73).

37/ Using CCD images from Modra Observatory we analysed 3 known cases of split comets - 73P/Schwassman-Wachman 3 (3 fragments), 51P/Harrington (2 fragments) and C/1999 S4 (Linear) which suddenly split into dozens of small pieces and disintegrated completely on late July 2000 (paper No. 82).

38/ Within the project to obtain precise astrometrical positions of the selected comets and asteroids, there were reduced 333 precise positions of comets and 127 precise positions of minor planets (papers Nos. 29, 30, 38, 54 and 60).

39/ 75 measurements of bright comets 1P/Halley, 23P/Brorsen-Metcalf and C/1989 X1 (Austin) was used to derive atmospheric extinction at the Skalnate Pleso Observatory. The two-component model of atmospheric extinction was confirmed. The model is a superposition of a more or less constant component of Rayleigh scattering on temporary clumps of molecules of air and a heavily variable component of scattering on dust particles - aerosols (paper No. 25).