Brightness variability in polar circumbinary disks

In binary systems with a strongly misaligned disk, the central binary stars can travel a significant vertical distance above and below the disk’s orbital plane. This can cause large changes in illumination of the disk over the course of the binary orbital period. We use both analytic and radiative transfer models to examine the effect of changes in stellar illumination on the appearance of the disk, specifically in the case of the polar disk HD 98800B. We find that the observed flux from the disk can vary significantly over the binary orbital period, producing a periodically varying light curve that peaks twice each binary orbit. The amount of flux variation is strongly influenced by the disk geometry. We suggest that these flux variations produce several observable signatures, and that these observables may provide constraints on different properties of the disk, such as its vertical structure, geometry, and cooling rate.