  We studied the light-induced effects in BiFeO$_3$ single crystals as a
function of temperature by means of optical spectroscopy. Here we report the
observation of several light-induced absorption features, which are discussed
in terms of the photostriction effect and are interpreted in terms of excitons.
The temperature dependence of their energy position suggests a possible
coupling between the excitons and the lattice vibrations. Moreover, there are
hints for anomalies in the temperature evolution of the excitonic features,
which might be related to the temperature-induced magnetic phase transitions in
BiFeO$_3$. Our findings suggest a coupling between light-induced excitons and
the lattice and spin degrees of freedom, which might be relevant for the
observed ultrafast photostriction effect in multiferroic BiFeO$_3$.
