  We present a systematic investigation of the electronic properties of bulk
and few layer ReS$_2$ van der Waals crystals using low temperature optical
spectroscopy. Weak photoluminescence emission is observed from two
non-degenerate band edge excitonic transitions separated by $\sim$ 20 meV. The
comparable emission intensity of both excitonic transitions is incompatible
with a fully thermalized (Boltzmann) distribution of excitons, indicating the
hot nature of the emission. While DFT calculations predict bilayer ReS$_2$ to
have a direct fundamental band gap, our optical data suggests that the
fundamental gap is indirect in all cases.
