Pulsating Soft Components in the Accreting X-ray Pulsars LMC X-4 and SMC X-1

Abstract

We report here spectral study of two accreting binary X-ray pulsars LMC X-4 and SMC X1 made with the Beppo-SAX observatory. The energy spectrum of both the pulsars in 0.1-10.0 keV band can be described by a model consisting of a hard power-law component, a soft excess and an iron emission line at 6.4 keV. In addition, the power-law component of SMC X-1 also has an exponential cutoff at ~ 6 keV. Pulse-phase resolved spectroscopy confirms a pulsating nature of the soft spectral components in both the pulsars, with a certain phase offset compared to the hard power-law component. Dissimilar pulse profiles of the soft and hard X-ray components and a phase difference between the pulsating soft and hard spectral components give evidences for different origins.