The minimum orbital period in thermal-timescale mass transfer
  We show that the usual picture of supersoft X-ray binary evolution as driven by conservative thermal-timescale mass transfer cannot explain the short orbital periods of RX J0537.7-7034 (3.5 hr) and 1E 0035.4-7230 (4.1 hr). Non-conservative evolution may produce such periods, but requires very significant mass loss, and is highly constrained. 
A.R. King (1), K. Schenker (1), U. Kolb (2), M.B. Davies (1) ((1)   University of Leicester, (2) Open University)