2009ApJ...690.1730A

The three-dimensional (3D) Radioastronomical Approach to Doppler tomography has been used to study the Hα 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 V_z= ±150 km/s, and demonstrates that the bulge is not confined to the orbital plane although it achieves a maximum strength near V_z= 0 km/s. 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 in the disklike state. The disk emission is seen over a range of V_zvelocities, 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.