Abstract Details

Name: Nazma Islam
Affiliation: Nicholas Copernicus Astronomical Centre, Warsaw, Poland
Conference ID: ASI2017_1204
Title : The many facets of variabilities in X-ray binaries
Authors and Co-Authors : NA
Abstract Type : Thesis
Abstract Category : Thesis
Abstract : An important property of X-ray binaries is intensity variations of different magnitudes in a wide range of timescales from milliseconds (quasi-periodic oscillations, millisecond pulsations), to a few weeks (orbital and super-orbital modulations) or longer (outbursts etc). In this thesis, different types of variabilities of X-ray binaries are considered in X-ray binary population studies and to investigate certain aspects of some individual systems. 1. We report results from an investigation of energy resolved orbital intensity profiles and from exhaustive orbital phase resolved spectroscopic measurements of GX 301-2 with MAXI-GSC. A very large equivalent width of the iron line along with a small value of the column density in the orbital phase range 0.10-0.30 after the periastron passage indicates an asymmetry in the distribution of the matter around the neutron star. 2. For the HMXB system IGR J16393–4643, we found a short eclipse in the Swift–BAT light-curve and utilised it to constrain the orbital inclination of the system. We have also studied, for the first time, broad-band pulsation and spectral characteristic of the system with a Suzaku observation, showing sub-orbital intensity variations. For the eclipsing and non-pulsing HMXB 4U 1700-37, the orbital evolution is studied using mid-eclipse times from archival as well as from long term light-curves of X-ray all sky monitors. Since no pulsations are detected in this system, it is difficult to estimate its orbital parameters, especially its eccentricity. Using mid-eclipse times from 10 years of Swift–BAT data, we have independently constrained the eccentricity of the binary system. 3. Using 16 years light-curves of X-ray binaries in 2-10 keV energy band of RXTE-ASM , multiple snapshots of X-ray binary luminosity functions of the Milky Way are constructed instead of averaging the luminosities, an improvement over previous analysis by Grimm et al. (2002). We found that the averaged luminosities of highly variable X-ray binaries do not represent their true positions in XLFs and the variability of X-ray binaries do indeed significantly affect the luminosity functions. 4. The averaged spectra of X-ray binaries using MAXI-GSC data are studied and used for constructing the composite X-ray spectrum. These composite X-ray binary spectra are useful in constraining the contribution of X-ray binaries in extra-galactic SEDs constructed from the simultaneous Chandra / XMM–Newton and NuSTAR observations of these galaxies. These SEDs will also serve as a useful input in estimating the contribution of X-ray binary heating at high redshift IGM during the Epoch of Re-ionization.