Timing and Pulse Profile Analysis of the High-Mass X-Ray Binary Vela X-1 Using RXTE/PCA Observations in 2008

Abstract

The present article presents timing and pulse profile study of high-mass X-ray binary Vela X-1 using the observation of the RXTE/PCA in 2008. Vela X-1 is a high-mass X-ray binary system, which is a wind-accreting system and is composed of a neutron star and a giant supergiant companion. The periodic pulsations and high variability of the system are due to accretion of the stellar wind of the companion star. RXTE/PCA data was also analyzed by timing analysis to estimate the pulse period of the source. The optimal pulse period was adjective based on the light curve data with the help of the efsearch task. Pulse profiles were also constructed by deriving the light curves of the various levels and folding them with the pulse period calculated. To examine variations in pulse structure with energy, pulse profiles were formulated as energy dependent profiles in several energy bands. In addition, long-term variability of the source was also studied depended on the data of ASM light curve. The measurements indicate that there are considerable differences in pulse profile morphologies across the different energy bands. Multi-peaked and complex structures were found to be more complex at lower energy and simple at high energy. These changes could have changed accretion processes and geometry of emission of the Vela X-1 system. The article sheds light on the behavior of emission as well as the process of accretion of high-mass X-ray binary systems.