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 over 66 nights. The mean value of the 3.5 hr photometric period was 0.14640 (+/-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 much too high to be consistent with period measurements in previous years. New spectroscopic observations confirm the radial velocity curve and 0.138d period found by Kraft in 1962. The low amplitude in v(rad) and the relatively narrow emission lines require a very low binary inclination; i approximately 20-degrees is likely. The inequality of photometric and spectroscopic periods is thus established beyond doubt and is the outstanding puzzle. But it seems possible to understand the photometric modulation in terms of a model originally developed for the ''superhumps'' in dwarf novae: the result of an eccentric accretion disk, forced to precess by the secondary's gravitational perturbation. The drifting period could arise from small changes in the outer radius of the disk. The data appear to be in reasonable agreement with the period-magnitude relation shown by dwarf novae in superoutburst. But confidence in this test will require an improved calibration of the photometry, and assessment of the possibility of a nonaccretion component of the luminosity. We review the present membership rolls of superhumping cataclysmic variables. It is very likely that this syndrome is not restricted to dwarf novae; indeed, it is nearly universal among stars of high M and short orbital period. It may be true that a general period-magnitude relation exists, possibly with dP/dm is-proportional-to P2; this is consistent with a simple theory of apsidal advance. The observed relationship between orbital and superhump periods seems to be consistent with the same theory, if the lobe-filling secondaries are slightly larger than predicted by the ZAMS mass-radius relation. Four of the superhumpers may possess tilted accretion disks, with a regressing line of nodes.