Ultraviolet, visible, infrared and X-ray observations of SCO X-1.

The first UV spectroscopic observations of the X-ray source Scorpius X-1, obtained with the IUE satellite, are presented. The UV data consist of low-resolution spectra in the 1150-3200 A wavelength range, and show emission lines arising in Si II and IV; C III and IV; N III, IV, and V; O IV and V, and He II. Also discussed are observations using visible photometry and spectroscopy, and infrared and X-ray photometry. Significant changes between the strengths of the emission lines with phase are observed when the source changes its UV and optical brightness. Significant variations are also observed in the UV continuum brightness of Sco X-1 which approximately match those observed simultaneously in the visible B band. The color excess of Sco X-1 is found to be 0.35 plus or minus 0.05, and the UV continuum energy distribution is shown to be well fitted by a bremsstrahlung distribution.