Radial velocity studies of close binary stars. IV.

Radial velocity measurements and sine-curve fits to the orbital velocity variations are presented for the fourth set of 10 close binary systems: 44 Boo, FI Boo, V2150 Cyg, V899 Her, EX Leo, VZ Lib, SW Lyn, V2377 Oph, Anon Psc (GSC 8-324), and HT Vir. All systems are double-lined spectroscopic binaries, with only two of them not being contact systems (SW Lyn and GSC 8-324) and five (FI Boo, V2150 Cyg, V899 Her, EX Leo, and V2377 Oph) being the recent photometric discoveries of the Hipparcos project. Five of the binaries are triple-lined systems (44 Boo, V899 Her, VZ Lib, SW Lyn, and HT Vir). Three (or possibly four) companions in the triple-lined systems show radial velocity changes during the span of our observations, suggesting that these are in fact quadruple systems. Several of the studied systems are prime candidates for combined light and radial velocity synthesis solutions.