  We report the discovery of photometric oscillations in the host star of the
exoplanet WASP-33 b (HD 15082). The data were obtained in the R band in both
transit and out-of-transit phases from the 0.3-m telescope and the Montcabrer
Observatory and the 0.8-m telescope at the Montsec Astronomical Observatory.
Proper fitting and subsequent removal of the transit signal reveals stellar
photometric variations with a semi-amplitude of about 1 mmag. The detailed
analysis of the periodogram yields a structure of significant signals around a
frequency of 21 cyc per day, which is typical of delta Scuti-type variable
stars. An accurate study of the power spectrum reveals a possible
commensurability with the planet orbital motion with a factor of 26, but this
remains to be confirmed with additional time-series data that will permit the
identification of the significant frequencies. These findings make WASP-33 the
first transiting exoplanet host star with delta Sct variability and a very
interesting candidate to search for star-planet interactions.
