The accretion activity of the Ae Herbig star CQ Tau

Results of spectral observations of the isolated Ae Herbig star CQ Tau obta ined in 1995-1998 in the H-alpha line and near the sodium resonance doublet are presented, together with simultaneous photometric monitoring ng of the star. CQ Tau is a member of the family of young UX Ori stars with nonperio dic Algol-like brightness decreases. The star is surrounded by an accretion disk, in which its emission-line spectrum and part of its absorption-line spectrum are formed. The strong variability of the H-alpha, D NaI, and HeI 5876 Angstrom lines testifies that the gaseous disk is appreciably inhomoge neous in both the radial and azimuthal directions. This inhomogeneity proba bly results from uneven feeding by the circumstellar material from the peri pheral regions of the circumstellar disk. Over the four years of observatio ns, we observed the star in deep minima three times (Delta V similar to 2). On these nights, an increase in the H-alpha equivalent width followed the decrease in radiation flux. In the two deepest minima, the normally two-com ponent line profile had only a single component with a nearly symmetrical p rofile. This behavior of the H-alpha line is in good agreement with the res ults of numerical modeling of Algol-like minima and can be used to estimate the parameters of the dust clouds eclipsing the star and inner accretion d isk. These estimates suggest that the circumstellar dust clouds can approac h very close to the star and be sublimated there. (C) 2000 MAIK "Nauka/lnte rperiodica".