Changes in the structure of the accretion disc of HS1804+67 through the outburst cycle

Abstract

We report on the analysis of high-speed photometry of the dwarf-nova HS1804+67 through its outburst cycle with eclipse mapping techniques. Eclipse maps show evidences of the formation of a spiral structure in the disc at the early stages of the outburst and reveal how the disc expands during the rise until its fills most of the primary Roche lobe at maximum light. During the decline phase, the disc becomes progressively fainter as the cooling front moves inwards from the outer regions, until only a small bright region around the white dwarf is left at minimum light. The variable part of the uneclipsed light is possibly due to emission in a wind emanating from the inner parts of the disc. The emission from this region is sensitive to the mass accretion rate.