O. I. Sharova

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(Vx,Vy,Vz) of the interacting Algol binary system U Coronae Borealis has been restored in 3D velocity space with resolutions of 30 km s-1 in Vx and Vy and 110 km s-1 in Vz. 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 (Vz ~ 200 km s-1) with strong emission intensity has also been discovered moving in the direction across the orbital plane of the system.

Three-Dimensional Doppler Images of the Disklike and Streamlike States of U Coronae Borealis

The three-dimensional (3D) Radioastronomical Approach to Doppler tomography has been used to study the H? emission sources in U Coronae Borealis. These 3D tomograms provide greater resolution than the projected two-dimensional version and highlight the jetlike gas flows in the V z direction transverse to the orbital plane. In this paper, the 3D tomograms are compared at two distinct epochs when U CrB was in the disklike state (1993 data) and the streamlike state (1994 data). Both states display a prominent emission source, the circumprimary bulge, which is produced when the gas stream strikes the photosphere of the mass gainer. This source is detected within Vz = ?150 km s?1, and demonstrates that the bulge is not confined to the orbital plane although it achieves a maximum strength near Vz = 0 km s?1. Other emission sources include the stream-star and stream-disk shocks and a Localized Region (LR) where the circling disk material strikes the incoming gas stream. The LR has V z velocities of 200-500 km s?1 in the disklike state. The disk emission is seen over a range of V z velocities, and there is evidence that the disk is inclined to the orbital plane or may have two arms. The gas stream flows along its predicted trajectory in the streamlike state, and a comparison with the disklike state suggests that the gas stream has a higher density than the disk in both states of this binary.

The radio continuum evolution in the planetary nebulae

The radio continuum variations from galactic planetary nebulae in the process of the central star evolution without helium flashes are considered. On the base of our distance scale we obtained empirical evolutionary dependences for the ionized mass and the hydrogen atom concentration. The parameters of a theoretical model of the interacting stellar winds (ISW) are determined to reach an agreement between empirical and theoretical dependences. In this model the time dependences are obtained for the intrinsic flux density at 15 v GHz and for the critical frequency. The flux density may increase with rate of several percents until the kinematic age does not exceed 1000 years.

Three-dimensional Doppler tomograms and detection of motions beyond the orbital plane in close binary systems

The newly developed radioastronomical approach (RA) has been modified for the reconstruction of three-dimensional (3D) Doppler tomograms. The RA permits an unequal space distribution of the views of an object and a reduction in the number of required orbital phases when compared with the filtered back-projection technique. The 3D Doppler tomogram of the close binary system U Coronae Borealis was reconstructed on the basis of 47 spectra of the Hα line. The three strongest Hα emission features found on the map were the accretion annulus, the gas stream moving along the ballistic trajectory, and a high-intensity region moving at high velocity in a direction across the orbital plane. It was not possible to discover this latter feature using standard two-dimensional Doppler tomography. The new RA technique is a useful tool for the subsequent study of gas flows in close binary systems.

The state of the art of distances to galactic planetary nebulae

Abstract New methods of determining the distances to galactic planetary nebulae have been analyzed and various statistical distance scales have been compared.