Physical parameters of close binary systems: VIII

ABSTRACT This paper presents the results of a combined spectroscopic and photometric study 20 contact binary systems: HV Aqr, OO Aql, FI Boo, TX Cnc, OT EE Cet, RW Com, KR V401 Cyg, V345 Gem, AK Her, V502 Oph, V566 V2612 V1363 Ori, V351 Peg, V357 Y Sex, V1123 Tau, W UMa, which was conducted in frame UMa Project. Together with 51 already covered by project an additional 67 existing literature, these systems bring total number binaries known solutions to 138. It found that mass, radius, luminosity components follow certain relations along MS new empirical power are extracted. We 30 per cent current sample show extreme values their parameters, expressed mass ratio or fill-out factor. shows that, among studied, some have extremely low (q < 0.1) ultrashort orbital period (Porb 0.25 d), expected evidence transfer progress. The evolutionary status is discussed aid correlation diagrams physical parameters compared those entire binaries. existence very short periods confirms slow nature merging process, seems explain why still exist as stars configurations even after several Gyr evolution.