  The luminous X-ray binary and black-hole candidate LMC X-1 has been observed
with the Rossi X-ray Timing Explorer (RXTE) to search for quasi-periodic
oscillations (QPO), previously reported in its high state. The source was
observed monthly in a series of nine observations. Analysis of the temporal
variations shows no evidence for QPO or other periodic changes, but
correlations between the high-energy light curve and hardness of the spectrum
are described. Spectral fits with two-component models demonstrate that the
hardness variations come from changes in the intensity of the high-energy
power-law tail.

Astrophysics