Observations of outbursts from the recurrent X-ray transient A0538-66 and LMC X-4

Abstract

Nine X-ray outbursts from the LMC have been observed with the HEAO 1 Large-Area Sky Survey Instrument. Some are shown to originate in the recurrent transient A0538-66, confirming the proposed 16 day periodicity and showing that the duration of the events can be as long as 14 days or as short as a few hours. Deviations from precise periodicity can be attributed to phase jitter or to a change in period occurring around the time of an exceptionally long outburst. Other outbursts which are irregular and consistently shorter originate in LMC X-4. A long-term light curve indicates that the LMC X-4 outbursts occur only when the source is in a high state, but are not strongly correlated with the binary phase.