Three-dimensional Doppler Tomogram of Gas Flows in the Algol-Type Binary U Coronae Borealis

The reconstruction of three-dimensional (3D) Doppler tomograms based on observational data has been accomplished for the first time. The distribution of the Hα emission intensity I(V_x,V_y,V_z) of the interacting Algol binary system U Coronae Borealis has been restored in 3D velocity space with resolutions of 30 km s^-1 in V_x and V_y and 110 km s^-1 in V_z. The reconstruction was based on 47 Hα spectra from 1994 by applying the developed radioastronomical approach (RA) to few-projections tomography. The comparison between the previous 2D and our 3D Doppler tomograms shows similarities with the main structural features of the gas flows in the orbital plane. Specifically, the gas stream along the ballistic trajectory and equatorial emission centered on the primary star are displayed on the 3D Doppler tomogram as distinct emission sources. A high-velocity stream (V_z ~ 200 km s^-1) with strong emission intensity has also been discovered moving in the direction across the orbital plane of the system.