We present the results of the timing and spectral analysis of X-ray high-state observations of the high-mass X-ray pulsar SMC X-1 with Chandra , XMM-Newton , and ROSAT , taken between 1991 and 2001 .
The source has L _ { X } \sim ( 3 – 5 ) \times 10 ^ { 38 } ergs s ^ { -1 } , and the spectra can be modeled as a power law plus blackbody with kT _ { BB } \sim 0.18 keV and a reprocessed emission radius R _ { BB } \sim 2 \times 10 ^ { 8 } cm , assuming a distance of 60 kpc to the source .
Energy-resolved pulse profiles show several distinct forms , more than half of which include a second pulse in the soft profile , previously documented only in hard energies .
We also detect significant variation in the phase shift between hard and soft pulses , as has recently been reported in Her X-1 .
We suggest an explanation for the observed characteristics of the soft pulses in terms of precession of the accretion disk .