A solution to the transition phase in classical novae

Abstract

One century after the discovery of quasi-periodic oscillations in the optical light curve of Nova GK Per 1901 the cause of the transition phase in a certain part of the nova population is still unknown. Three years ago we suggested a solution for this problem and proposed a possible connection between the transition phase and intermediate polars (IPs). About 10 percent of the cataclysmic variable population are classified as IPs, which is consistent with the rarity (about 15 percent) of the transition phase in novae. Recent observations of three novae seem to support our prediction. The connection is explained as follows: The nova outburst disrupts the accretion disc only in IPs. The recovery of the disc, a few weeks-months after the eruption, causes strong winds that block the radiation from the white dwarf, thus dust is not destroyed. If the winds are very strong as is probably the case in DQ Her (perhaps since its spin period is very short) this leads to a dust minimum.