Doppler tomography of the dwarf novae VY Aquari and WX Ceti

Abstract

Aims. We present the optical spectroscopy of the dwarf novae VY Aqr and WX Cet in quiescence. Methods. For the first time for VY Aqr, we construct the Doppler tomograms for the Hα ,H β, and He I 5875 A emission lines. Results. The tomograms reveal complex emission structures that can be identified with the accretion disc, the bright spot and, in the case of VY Aqr, the secondary star. For the first time, the white dwarf is detected unambiguously in the spectrum of VY Aqr, and we confirm the long-lasting condition of the emission spot in the leading side of the WX Cet disc. For VY Aqr, we found that the bright spot influences the Hα emission even at the large velocities far from the line center, introducing a spurious effect in the diagnostic diagram and ephemeris zero point. We calculate averaged Hα emissivity gradients in the discs and disc sizes and compare our results to previous investigations on these objects.