  We present limits on transit timing variations and secondary eclipse depth
variations at 8 microns with the Spitzer Space Telescope IRAC camera. Due to
the weak limb darkening in the infrared and uninterrupted observing, Spitzer
provides the highest accuracy transit times for this bright system, in
principle providing sensitivity to secondary planets of Mars mass in resonant
orbits. Finally, the transit data provides tighter constraints on the
wavelength- dependent atmospheric absorption by the planet.
