Interpretation of light curves of IP Peg in a model with shockless interaction between the gas stream and disk

We have analyzed light curves of the eclipsing cataclysmic variable IP Peg. A model with a shockless interaction between the gaseous stream and disk (i.e., an elliptical disk with a “hot line”) can describe the main characteristic features of the light curve of the interacting close binary better than a classical model with a “hot spot” at the outer boundary of a circular accretion disk. In particular, the hot-line model can reproduce the luminosity increase observed at phases ?～0.1–0.2 and ?～0.5–0.6, which is not possible in the standard hot-spot model. The advantages of the hot-line model are particularly striking for the IR light curves of IP Peg: the discrepancy χ² between the theoretical and observed light curves is 49 for the model with a shockless interaction between the gaseous stream and disk, and 2681 for the standard hot-spot model.