We present the results of two extensive Rossi X-ray Timing Explorer observations of large X-ray flaring episodes from the high-mass X-ray binary pulsar LMC X-4 .
Light curves during the flaring episodes comprise bright peaks embedded in relatively fainter regions , with complex patterns of recurrence and clustering of flares .
We identify precursors preceding the flaring activity .
Pulse profiles during the flares appear to be simple sinusoids , and pulsed fractions are proportional to the flare intensities .
We fit Gaussian functions to flare peaks to estimate the mean full-width-half-maximum to be \sim 68 s. Significant rapid aperiodic variability exists up to a few hertz during the flares , which is related to the appearance of narrow , spiky peaks in the light curves .
While spectral fits and softness ratios show overall spectral softening as the flare intensity increases , the narrow , spiky peaks do not follow this trend .
The mean fluence of the flare peaks is ( 3.1 \pm 2.9 ) \times 10 ^ { 40 } ergs in the 2.5–25 keV energy range , with its maximum at \sim 1.9 \times 10 ^ { 41 } ergs .
The flare peak luminosity reaches up to ( 2.1 \pm 0.2 ) \times 10 ^ { 39 } ergs s ^ { -1 } , far above the Eddington luminosity of a neutron star .
We discuss possible origins of the flares , and we also propose that inhomogeneous accretion columns onto the neutron star polar caps are responsible for the observed properties .