  The Shastry-Sutherland model, which provides a representation of the magnetic
properties of SrCu$_2$(BO$_3$)$_2$, has been studied by series expansion
methods at T=0. Our results support the existence of an intermediate phase
between the N\'eel long-range ordered phase and the short-range dimer phase.
They provide strong evidence against the existence of helical order in the
intermediate phase, and and somewhat less strong evidence against a
plaquette-singlet phase. The nature of the intermediate phase thus remains
elusive. It appears to be gapless, or nearly so.
