Spectral and timing studies of 2S 1417-624 during a giant outburst

TL;DR

This study analyzes the spectral and timing behavior of the X-ray pulsar 2S 1417-624 during a giant outburst, revealing energy-dependent pulse profiles, spin-up behavior, and spectral changes linked to luminosity variations.

Contribution

It provides the first detailed timing and spectral analysis of 2S 1417-624 during a giant outburst, highlighting changes in pulse profiles and beam configurations with luminosity.

Findings

Pulse profiles evolved from double to triple peaks and back during the outburst.

The pulsar exhibited spin-up during the outburst.

Spectral analysis showed a power law with high energy cutoff and iron line at 6.4 keV.

Abstract

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 {\it Rossi X-ray Timing Explorer (RXTE)} 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 anti-correlation 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 cutoff 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.