  The delta Scuti star X Caeli has been the target of a simultaneous
photometric (14 consecutive nights) and spectroscopic campaign (8 consecutive
nigths). From the analysis of light curves we were able to pick up 17 frequency
components, most of which were already detected in two previous campaigns. The
comparison with the results of the previous campaigns shows that while some
terms are rather stable (in particular the dominant mode at 7.39 c/d) others
have conspicuous amplitude variations. 14 photometric terms have been also
detected in the radial velocity curve or in the analysis of the line profile
variations. There are no spectroscopic terms without photometric counterparts,
and this means that there are no high--degree modes as observed in other delta
Scuti stars. The simultaneous fit of light and line profile variations has
allowed the estimation of the inclination of rotational axis (about 70 deg.)
and the l,m identification for many modes. In particular there is clear
evidence that the two shortest period modes are retrograde. Rather reliable
results were found for the dominant mode which has l=1, m=-1. The resulting
physical parameters of its pulsation are in good agreement with the prediction
of theoretical models and suggest for this star a mixing length parameter of
about 0.5. Finally the fundamental stellar physical parameters and their
refinement are discussed in the light of the identification of the 7.47 c/d
term as a radial mode.
