U Gem - Rediscussion of radial velocities and system parameters

Radial velocities measured from peaks of the emission lines (Smak 1976, Sto ver 1981), analyzed within the three-body approximation, give K-1 consisten t with that measured directly from the absorption lines of the white dwarf (Long and Gilliland 1999). This implies that the three-body approximation i s essential for correct description of the outer parts of the disk. Wings o f the emission lines profiles are likely to be contaminated by contribution s from parts of the stream which are overflowing the disk close to the whit e dwarf. Radial velocities measured from wings (Kraft 1962, Stover 1981), a nalyzed only in phase intervals free of contamination, give K-1 consistent with other determinations. New analysis of the spot eclipses gives i = 69 degrees +/-2 degrees and sho ws that during outburst the disk expands up to about r(d) approximate to0.4 0-0.45 approximate to0.9 r(Roche), while during quiescence it contracts fro m r(d) approximate to 0.75 r(Roche) to r(d) approximate to 0.65 r(Roche). H owever, the radius of the disk during quiescence obtained from V-d sin i ap pears larger: r(d) approximate to 0.85-0.95 r(Roche). System parameters are: M-1 = 1.07 +/-0.08 M-circle dot, M-2 = 0.39 +/-0.02 M-circle dot, R-1 = 4.7 +/-0.7x 10(8) cm, R-2 = 0.45 +/-0.01 R-circle dot, and distance d = 96 +/-4 pc. The radius of the secondary component, when co mpared with its mass, shows that the secondary is a normal main sequence st ar.