Photometric activity of CQ Tau on the time interval of 125 years

The star CQ Tau belongs to the family of UX Ori type stars. It has very complex photometric behavior and complex structure of the circumstellar environment. In our paper we constructed the historical 125 years light curve of this star basing on the published photometric observations. It follows that besides a random component characteristic of UX Ori type stars, the large amplitude periodic component with the 10 year period is also present. Its existence was suspected earlier in [11]. New observations confirm its reality. It points to an existence of the second component close to the star. The density waves and matter flows caused by the companion motion lead to periodic changes in the circumstellar extinction and brightness of the star. This result is discussed in context of the recent observations of CQ Tau with high angular resolution.Comment: 7 pages, 4 figures, accepted by Astrophysic

Surface photometry of new nearby dwarf galaxies

We present CCD surface photometry of 16 nearby dwarf galaxies, many of which were only recently discovered. Our sample comprises both isolated galaxies and galaxies that are members of nearby galaxy groups. The observations were obtained in the Johnson B and V bands (and in some cases in Kron-Cousins I). We derive surface brightness profiles, total magnitudes, and integrated colors. For the 11 galaxies in our sample with distance estimates the absolute B magnitudes lie in the range of -10>Mb>-13. The central surface brightness ranges from 22.5 to 27.0 mag/sq.arcsec. Most of the dwarf galaxies show exponential light profiles with or without a central light depression. Integrated radial color gradients, where present, appear to indicate a more centrally concentrated younger population and a more extended older population.Comment: accepted by A&

The Unique Eclipsing System KH 15D: New Photometric Data

We present results of the photometric observations of the young eclipsing binary KH 15D obtained during the two observational seasons of 2002-2004 years. A comparison of our data with those by Hamilton et al. (2001) and Herbst et al. (2002) reveals an existence of the long-term photometrical brightness trend: during 5 years a system brightness in the I band decreased by about one stellar magnitude. It is also shown that a systematic change of the eclipse parameters found by Herbst et al. (2002) is continuing up to now. The shape of the light curve did not change essentially and is characterized with a small brightening in the central part of the eclipses. The results obtained are discussed in the context of the current models of KH 15D.Comment: 7 pages, 3 figures, Accepted by Astrophysic

Modulation of Circumstellar Extinction in a Young Binary System with a Low-Mass Companion in a Noncoplanar Orbit

The cyclic activity model of a young star with the low-mass secondary component (q = M2/M1 <= 0.1) accreting a matter from circumbinary disk is considered. It is assumed that the orbit is circular and the disk and orbital planes are non-coplanar. Sets of hydrodynamics models of such a system have been calculated by the SPH method and then the variations of the circumstellar extinction and phase light curves were determined. The calculations showed that depending on the model parameters and orientation of the system in regards to an observer the different in shape and amplitude light curves can be observed. An important property of the considered models is also the dependence of the mass accretion rate onto the components on the phase of the orbital period. The results of the calculation can be used for analysis of the cyclic activity of UX Ori stars and young stars with the long-lasting eclipses.Comment: 14 pages, 7 figure

NGC 7468: a galaxy with an inner polar disk

We present our spectroscopic observations of the galaxy NGC 7468 performed at the 6-m Special Astrophysical Observatory telescope using the UAGS long-slit spectrograph, the multipupil fiber spectrograph MPFS, and the scanning Fabry-Perot interferometer (IFP). We found no significant deviations from the circular rotation of the galactic disk in the velocity field in the regions of brightness excess along the major axis of the galaxy (the putative polar ring). Thus, these features are either tidal structures or weakly developed spiral arms. However, we detected a gaseous disk at the center of the galaxy whose rotation plane is almost perpendicular to the plane of the galactic disk. The central collision of NGC 7468 with a gas-rich dwarf galaxy and their subsequent merging seem to be responsible for the formation of this disk.Comment: 8 pages, 6 figures, accepted in Astronomy Letters, 2004, vol 30., N 9, p. 58