Detection of Short Fading Episodes in Two Dwarf Novae from VSNET Observations

From the observations reported to VSNET, we detected short fading episodes intwo dwarf novae, RX And (orbital period 5.0 hr) and SU UMa (orbital period 1.8hr). The episodes in RX And can be naturally explained as the response to ashort-term reduction of the mass-transfer rate. A qualitative comparison withVY Scl-type fadings is also discussed. In SU UMa, the same explanation isexpected to be more difficult to apply. The viable, but still poorlyunderstood, possibilities include the temporary reduction of quiescent diskviscosity and the temporary reduction of mass-transfer rate. If the latterpossibility is confirmed, we probably need a different mechanism from that ofVY Scl-type stars.Comment: 5 pages, 3 figures, accepted for publication in PAS