2018MNRAS.479.5612G

We present the results obtained from timing and spectral studies of the accretion powered X-ray pulsar 2S 1417-624 during a giant outburst in 2009 by using Rossi X-ray Timing Explorer observations. X-ray pulsations were detected in the light curves obtained from all epochs of observations. The pulsar was found to be spinning-up during the outburst. The pulse profiles were observed to be strongly dependent on photon energy and luminosity. A double-peaked profile at lower luminosity evolved into a triple-peaked profile at the peak of the outburst which is further reverted back to a double-peaked structure during the decay of the outburst. An anticorrelation was also observed between the pulse fraction and the source flux. The 3-70 keV energy spectrum of pulsar was well described with a power law modified with high-energy cut-off model along with an iron fluorescence line at 6.4 keV. Based on the evolution of pulse profile, pulse fraction, and spectral parameters across observed luminosity, we interpret our results in terms of changes in the pulsar beam configuration from sub-critical to super-critical regimes.