2005MNRAS.363..285H

We present seven nights' blue (4300-5000Å) spectroscopy of the nova-like variable star V3885 Sgr. The line spectrum shows a typical combination of broad absorption and emission in Hγ, Hβ and Hei, which is associated with the accretion disc. We also observe antiphased narrow emission, which we attribute to irradiation of the secondary star. The Heiiλ4686 and Niii-Ciii-Civ emission lines are devoid of structure and are most likely formed in an outflow. We measure radial velocity shifts in the absorption and emission lines, from which we fit an orbital period of 4.97126±0.00036h. From the velocity semi-amplitudes of the disc and companion star, we are able to constrain the binary mass ratio to q > 0.7.

The phase-folded spectra provide dense coverage of the entire orbital cycle. Doppler tomograms of the hydrogen and Hei lines reveal spiral structure in the accretion disc and the irradiated donor star. We believe that this is the first unambiguous detection of spiral waves in a nova-like variable.