  We consider thin fluid films placed on thermally conductive substrates and
exposed to time-dependent spatially uniform heat source. The evolution of the
films is considered within the long-wave framework in the regime such that both
fluid/substrate interaction, modeled via disjoining pressure, and Marangoni
forces, are relevant. We analyze the problem by the means of linear stability
analysis as well as by time-dependent nonlinear simulations. The main finding
is that when self-consistent computation of the temperature field is performed,
a complex interplay of different instability mechanisms results. This includes
either monotonous or oscillatory dynamics of the free surface. In particular,
we find that the oscillatory behavior is absent if the film temperature is
assumed to be slaved to the current value of the film thickness. The results
are discussed within the context of liquid metal films, but are of relevance to
dynamics of any thin film involving variable temperature of the free surface,
such that the temperature and the film interface itself evolve on comparable
time scales.
