  The recent discovery of a transiting planet around WASP-33, the misalignment
of the stellar rotation axis and the planet orbit, the possible existence of an
additional planet in the system, and the presence of $\delta$ Scuti pulsations
in the hosting star make this system a highly interesting object to help us
understand the origin and evolution of giant planets orbiting very close a
star. High spatial resolution imaging allows the study of the presence of the
predicted additional planet, and any other objects, constraining the possible
formation scenarios of the system. In November 2010, we recorded high spatial
resolution images from 1 to 2.5 $\mu$m using the W.M. 10m-Keck II telescope and
its adaptive optics system, obtaining broad (Jc,Hc, and Kc) and narrow band
(FeII) images of the system. After data reduction, the contrast and angular
resolution provided by this instrument allowed us to constraint the
multiplicity of this system and to detect one potential companion. We have
found a new object at a distance of 1.961$"$ $\pm$ 0.003$"$ from the WASP-33,
with a position angle of 276.32$\pm$0.24 deg. It could be a dwarf star/ brown
dwarf or an extragalactic object. In the first case, and assuming the same
distance from the Sun, the object is 227 AU from the central star. On the other
hand, no additional objects have been found. This constraints the possible
objects in the system, depending on its age and masses. A potential companion
object to WASP-33 was obtained. The gravitational link must be confirmed, but
this object could influence the evolution of the planetary system depending on
its orbital eccentricity. We have ruled-out the existence of additional
objects, depending on the age of the system.
