An Equipotential Disk Model with Irradiation for Nova-like Variables

Abstract The reflection effect is here incorporated within an earlier analytic binary system light- and velocity-curve model that includes a circumstellar equipotential disk. The modeled disk is semitransparent, to explore the attenuation and reemission of irradiance within the disk, as well as the irradiance of the companion star. The reflection functions defined in R. E. Wilson ensure efficient computation and allow multiple reflection. A capsule summary of the general binary system potential problem provides a foundation for close binary morphological ideas. Chief among these ideas is that many or perhaps most postnovae may be of the double contact morphological type. The location of an outer-disk null point of effective gravity accurately quantifies a limit on disk size. The disk should not extend beyond the outer null point, as the local material would then be unbound to the disk. The disk’s inner extent is set by another null point. The inner and outer null locations are computed at each solution iteration, thus obviating any need for the arbitrary cutoffs seen in other postnova disk models. Remarkably, impersonal light-curve solutions find the disk edge quite close to the outer null point for U Scorpii (U Sco). Other reflection-related topics include irradiation heating and measurement of disk interior density and temperature. Analyses find white dwarf masses about 3%–6% lower than in nongravitating disk models that implicitly include disk mass as part of the white dwarf. The results from CI Aquilae and U Sco analyses are tabulated and prospects for further progress are outlined.