THE 1991 V603 AQUILAE CAMPAIGN - SUPERHUMPS AND P-DOTS

We report the results of an intensive program of photometry of the old nova V603 Aquilae during 1991. The coverage totaled 207 hr, spread ov er 66 nights. The mean value of the 3.5 hr photometric period was 0.14 640 (+/-6) days, but the instantaneous value increased over the course of the 5 month observing season. This is a drift in the period rather than a truly secular effect, since the observed rate of increase is m uch too high to be consistent with period measurements in previous yea rs. New spectroscopic observations confirm the radial velocity curve a nd 0.138d period found by Kraft in 1962. The low amplitude in v(rad) a nd the relatively narrow emission lines require a very low binary incl ination; i approximately 20-degrees is likely. The inequality of photo metric and spectroscopic periods is thus established beyond doubt and is the outstanding puzzle. But it seems possible to understand the pho tometric modulation in terms of a model originally developed for the ' 'superhumps'' in dwarf novae: the result of an eccentric accretion dis k, forced to precess by the secondary's gravitational perturbation. Th e drifting period could arise from small changes in the outer radius o f the disk. The data appear to be in reasonable agreement with the per iod-magnitude relation shown by dwarf novae in superoutburst. But conf idence in this test will require an improved calibration of the photom etry, and assessment of the possibility of a nonaccretion component of the luminosity. We review the present membership rolls of superhumpin g cataclysmic variables. It is very likely that this syndrome is not r estricted to dwarf novae; indeed, it is nearly universal among stars o f high M and short orbital period. It may be true that a general perio d-magnitude relation exists, possibly with dP/dm is-proportional-to P2 ; this is consistent with a simple theory of apsidal advance. The obse rved relationship between orbital and superhump periods seems to be co nsistent with the same theory, if the lobe-filling secondaries are sli ghtly larger than predicted by the ZAMS mass-radius relation. Four of the superhumpers may possess tilted accretion disks, with a regressing line of nodes.