  Hard-photon (E$_{\gamma}>$ 30 MeV) emission from second-chance
nucleon-nucleon Bremsstrahlung collisions in intermediate energy heavy-ion
reactions is studied employing a realistic thermal model. Photon spectra and
yields measured in several nucleus-nucleus reactions are consistent with an
emission from hot nuclear systems with temperatures $T\approx$ 4 - 7 MeV. The
corresponding caloric curve in the region of excitation energies
$\epsilon^\star\approx$ 3{\it A} - 8{\it A} MeV shows lower values of $T$ than
those expected for a Fermi fluid.
