Spectral Variations and Physical Conditions of by Draconis in the Ultraviolet

We present International Ultraviolet Explorer (IUE) observations during the period (1980 - 1994) of the double lined spectroscopic binary BY Dra to show the spectral behavior and physical conditions in its atmosphere. The observations reveal indication of flare activity in their flux values in years (1981-1990-1994) in the chromosphere and transition region of the primary star. Beside the flaring activity the emission lines show a range of variations between high, intermediate and low. There is a relation between the fluxes and rotational phase. The reddening of BY Dra was estimated from 2200 Å absorption feature to be E(B - V) = 0. The average mass loss rate is found to be ~4.9⋅10^-8 M_⨀ yr^-1, the average temperature of the emitting region to be ~9.2⋅10⁴ K, energy of flare to be ~6.2⋅10³⁷ erg. We attributed the spectral variations to a cyclic behavior of the underlying magnetic field and the flaring activity to three component model.