We have determined the effective temperatures and surface gravities of the components of U Sge, using a combination of optical spectral scans and IUE spectra. The primary component is found to be a B7.5 V star with T e{{ = 12,250 (± 250) K and logg = 3.9 ± 0.1. The secondary component is of spectral type G4 III-IV. The best value for distance is 295 ± 20 pc, and the color excess is E(B-V) = 0™06. Our determination of the slope of the radial curve of the secondary star at primary eclipse

more »

... the previous results (mainly by Tomkin) that the mass ratio is very close to 3. Combination with photometric solutions enables us to derive reliable system parameters, given in Table VII . One high-dispersion IUE spectrum has been studied in greater detail. We have been able to fit selected lines of Fell, Sill, and Sim assuming solar abundances. The resonance doublet of C II at 1336 Á could not be fitted and we are investigating several possible explanations. The photospheric lines of the hotter component are broadened by rotation; we find u rot ae 100 km s -1 . We discovered emission lines of the W Serpentis type in an IUE spectrum taken in the total primary eclipse. Although the observed fluxes of these lines are very low, the powers emitted are half as strong as those seen in U Cep. This is rather surprising, since we did not find any other evidence of circumstellar matter or mass transfer activity.