Semi-detached binaries: The origin and present status of TU Mon,SX Cas,and DM Per

An attempt is made to trace back the possible progenitor systems of the Algol-type binaries TU Mon, SX Cas, and DM Per. The present characteristics are compared to the result of the evolution of 9M ₀+5.4M ₀. The position of the hot components in the HRD is discussed with regard to the theoretical models.Paper presented at the Lembang-Bamberg IAU Colloquium No. 80 on Double Stars: Physical Properties and Generic Relations, held at Bandung, Indonesia 3–7 June, 1983.