Abstract

Phase-resolved spectroscopic observations of BL Hyi obtained during the high mass transfer state are presented. The H?, He I 5875 and He I 6678 emission line profiles are analyzed with the Doppler tomography technique. It is shown that these emissions arise from a single region in the accretion stream. No emission from the secondary star, either in the H? or in the He I line, could be identified. The accretion column could not be detected on the tomographic reconstructions of the system. An orbital ephemeris based on the radial velocities of the Na ID emission line is derived, assuming a chromospheric origin in the secondary star. The spectroscopic observations provide a consistent picture of the accretion geometry in the system. Most of the optical emission line flux was found to be formed in a reservoir of low angular momentum gas filling a substantial fraction of the Roche lobe. Combining our results with literature data it was possible to constrain the absolute longitude of the magnetic axis in this classical polar.