X-Ray Timing and Spectral Measurements of the X-Ray Pulsar 4U:1538-52

The medium energy experiment onboard the EXOSAT satellite observed the X-ray binary system 4U 1538-52 on four occasions during March and August 1984. Observed pulsation periods indicate that the neutron star in the 4U 1538-52 system continued to spin down with P rate/P = 0.00023/yr in the period 1976 to 1988. The eclipse transition time of approximately 0.06 days gives a height of 1.5 times 10 to the 11th power cm for the atmosphere of the optical counterpart. The phase-average X-ray spectrum shows an iron line. The spectral form shows variations with pulse-phase.