Ultraviolet spectra of the X-ray transient A0538-66

Ultraviolet spectra were obtained before and after the optical spectrum changed from absorption to emission lines. The continuum brightness dropped by a factor of 2. Spectra with bright continua show N V, Si IV, and C IV in absorption, while the spectrum with fainter continuum has these lines in emission. The emission lines of N V and Si IV are anomalously bright compared with C IV. The brighter spectra indicate an effective temperatury of 25,000 K, while the fainter continuum indicates a somewhat lower temperature. Probable interstellar absorption lines due to galactic halo and the LMC interstellar medium are observed.