Late Superhumps in WZ Sge

The following message was sent by Dr. Tom Marsh (Dept. of Physics, University of Warwick) to the AAVSO Discussion Group on Wed., Aug. 15, 2001:

Dear Observers,

Its now the 22nd day of the WZ Sge outburst and quiescence must be coming soon. However rather than think its all over then, I wanted to encourage everyone looking at this star to carry on intensively now and well after the outburst because of an interesting paper by Rick Hessman and others on the dwarf nova OY Car. (Hessman et al. 1992, Astronomy & Astrophysics, 263, 147). In this paper they observed eclipses of the bright spot where the gas stream hits the disk after a superoutburst. This can be used to determine the radius at which the stream/disk impact occurs. This revealed that an elliptical disk remained even after the outburst. This disk precesses slowly relative to our line of sight and so varying radii are measured for the stream impact. We might be able to do the same for WZ Sge. It just requires as-fast-as-possible photometry in the lates stages and following the outburst (less than 1 minute exposure to exposure, preferably less than 30 seconds). If the superb coverage obtained so far keeps up, it may be possible to map out the shape of the disk in exquisite detail, which would be a nice finale to a great campaign.

Tom Marsh

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