Timing Analysis of X-ray Binaries

Abstract

Timing and spectral analysis can give us valuable information about the properties of a compact binary system, by studying the evolution of its parameters throughout the course of an observation or within sections of a single pulse. We have illustrated these nuances in the introductory chapter before moving on to our object of interest, GX 301-2. GX 301-2 is a neutron star belonging in a high mass X-ray binary system. It has a pulse spin period of about 686 seconds, and revolves around its companion Wray 977 (a B-type supergiant) in a highly eccentric orbit (e = 0.47), while accreting mass from the supergiant’s stellar wind. It has known to show flare ups at the pre-periastron when it passes through the dense stellar wind close to the Be disc of its companion Wray 977.

We have taken an observation from May 2010, when GX 301-2 was just in the post-apastron region of its orbit. The light curve of GX 301-2 showed an anomalous dip in its pulse, lasting for a very brief time- exactly 1 pulse period. The brevity of the dip as well as certain spectral characteristics leading up to it make it a very novel and interesting problem. We discuss why this is interesting, and perform timing and spectral analysis on this chunk of data to determine what the cause of such a dip could be.