  Using our extensive ROSAT X-ray observations of M33, we confirm a 3.45 day
eclipse period for the Einstein source X-7 (Larson & Schulman, 1997) and
discover evidence for a 0.31-s pulse period. The orbital period, pulse period
and observed X-ray luminosity are remarkably similar to SMC X-1. We therefore
suggest M33 X-7 is a neutron star high mass X-ray binary with a 15-40 Msol O/B
companion and a binary separation of 25-33 Rsol if the companion is almost
filling its Roche lobe.
