  The theoretical model by Sorasio et al. (2006) for the steady state Mach
number of electrostatic shocks formed in the interaction of two plasma slabs of
arbitrary density and temperature is generalized for relativistic electron and
non-relativistic ion temperatures. We find that the relativistic correction
leads to lower Mach numbers, and as a consequence, ions are reflected with
lower energies. The steady state bulk velocity of the downstream population is
introduced as an additional parameter to describe the transition between the
minimum and maximum Mach numbers in dependence of the initial density and
temperature ratios. In order to transform the soliton-like solution in the
upstream region into a shock, a population of reflected ions is considered and
differences to a zero-ion temperature model are discussed.
