  The radiation-driven warping instability discovered by Pringle holds
considerable promise as the mechanism responsible for producing warped,
precessing accretion disks in X-ray binaries. This instability is an inherently
global mode of the disk, thereby avoiding the difficulties with earlier models
for the precession. Here we follow up earlier work to study the linear behavior
of the instability in the specific context of a binary system. We treat the
influence of the companion as an orbit-averaged, quadrupole torque on the disk.
The presence of this external torque allows the existence of solutions in which
the direction of precession of the warp is retrograde with respect to disk
rotation, in addition to the prograde solutions which exist in the absence of
external torques.
