Spectral variability of LMC X-4

EXOSAT observations of the LMC X-4 region are reported. It is shown that the mean spectrum of LMC X-4, during the on state, is characterized by a hard power low with a high energy cut-off, a soft energy excess, and an iron emission line. During a very bright flare the spectrum was found to change the thermal bremsstrahlung. Pulse phase spectroscopy during this flare reveals the existence of two iron lines which change their separation with pulse phase and with the intensity of the continuum. The behavior is consistent with the assumption of symmetrical Doppler shifting. During other flares instantaneous phase shifts by approximately 180 deg are detected in the pulse profile. The consequences of these observations are discussed and compared to the situation in Her X-1.