Subfuors in Orion association

Results of spectral and photometric observations of Sugano star = V1143 Ori in brightness minimum and near it are given. Emission lines of HI, CaII, FeI, TiI, TiII and TiO absorption bands are detected. The appearing envelope is observed also in minimum. A brightness increase of Shanalstar V1118 Ori is observed. In its spectrum lines of HI, CaII, FeI, FeII are found, testifying to formation of an envelope.During the last ten years data on T Tau type stars which have fuor-like outburst-subfuors were obtained. Two such stars were found in Orion association. These are V1118 Ori [1] and V 1143 Ori [2,3]. In recent years, in Byurakan observatory observations of these stars have been made.

Axial rotation of BY Dra-type stars and related objects

Periods of the rotational modulation of the brightness of BY Dra-type stars, Pleiades spotted stars, naked T Tau stars and T Tau-type stars are compared with absolute bolometric stellar magnitudes. Arguments are given that the majority of BY Dra-type stars have the age of 10∗∗8 years and relatively fast as well as slowly rotating objects are met between them.

Quasi-Periodic Variations of Balmer Line Profiles in Spectra of the T Tau-Type Star RW Aurigae

RW Aur is one of the most active T Tau-type stars with essentially variable emission line spectrum. In order to study the nature of this variability,patrol spectroscopic observations of the star were carried outfrom November 1979 to March 1982 at the 2.6-meter telescope of the Crimean Astrophysical Observatory. The spectral region λλ38OO-67OO A has been observed with a dispersion of about 40 A/mm. All nights were supplied with simultaneous spectrophotometry of the star.

On Activities of UV Cet-Type Flare Stars and of T Tau-Type Stars

Comparisons of the activities of UV Cet-type flare stars and of T Tau-type stars with solar activity permits the conclusion that non-sta-tionary processes in the UV Cet-type stars and in the Sun are of an indent ical physical nature but that they differ qualitatively from active events in the T Tau-type stars. The identity of the activity in flare stars and the Sun makes it possible to study successfully stellar activity with the help of known models of various solar events and, on the other hand, to have a more general approach to the physics and evolution of solar activity on the basis of established features of numerous flare stars of different ages and masses. The hypothesis on hydromagnetic activity of the T Tau-type stars is sketched; within this framework, one supposes that the main feature of such stars is an occurrence at every point of the stellar surface, of conditions necessary for the existence of dark spots, i.e. a lowering of the photospheric brightness due to strong local magnetic fields.

Determination of the term Symbiotic Star

Symbiotic stars have been studied for many years. But the common determination of the term “symbiotic star” does not exist even now. Merrill (1958) introduced this term in order to emphasize unusual spectral features – absorption TiO bands and emission lines belonging to highly ionized ions.If we look on the eruptive stars spectra we well see absorption and emission features in the spectra of many stars which we cannot certainly consider as symbiotic stars. For example the U Gem type stars have absorption and emission features in their spectra. A similar situation exists in the case of the old novae. The T Tau type stars have many emission lines, and their spectral type corresponds to G-K. Even the long period variables have some emission lines though their spectral type is M. On the other hand, there are also the BQ[]type stars which are characterized by the presence in their optical spectrum of forbidden emission lines and of a rather hot absorption spectrum.

Stellar Magnetism: Some Observable, Expected and Suggested Effects of Magnetic Field in Eruptive Varaibles

Consideration of main stellar-statistical and astrophysical features of th UV Cet-type flare stars leads to a conclusion that the evolution of these variables, as well as other stars, is determined by their masses and chemical composition; a third essential evolution factor is the magnetic field which is responsible for all manifestations of flare activity.The main physical features of the T Tau-type stars can be understood in the framework of a hypothesis that these stars have large scale magnetic fields. Their strengths are close to a critical level at which the magnetic field and subphotospheric convection begin to interact strongly causing a significant decrease of the photospheric brightness, as in sunspots. Physical and genetic similarities of the UV Cet and T Tau stars are discussed withinth the framework of the idea of the essential role of stellar magnetism.