A Suzaku view of IGR J16393-4643

TL;DR

This study presents a detailed analysis of the highly absorbed pulsar IGR J16393-4643 using Suzaku data, revealing its orbital characteristics, energy-dependent pulse profiles, and spectral properties, including high absorption and phase-dependent spectral changes.

Contribution

First simultaneous broad-band pulsation and spectral analysis of IGR J16393-4643, providing insights into its orbital inclination, pulse morphology, and spectral variability.

Findings

Indicates the system may be eclipsing with a short eclipse semi-angle.

Pulse fraction increases with energy and shows complex, energy-dependent morphology.

Spectral analysis reveals high absorption and phase-dependent spectral index changes.

Abstract

The pulsar IGR J16393-4643 belongs to a class of highly absorbed supergiant HMXBs, characterised by very high column density of absorbing matter. We present the results of the simultaneous broad-band pulsation and spectrum analysis, from a 44 kilosec Suzaku observation of the source. The orbital intensity profile created with the SWIFT-BAT light-curve shows an indication of IGR J16393-4643 being an eclipsing system with a short eclipse semi-angle $\theta_{E} \sim$ 17$^{\circ}$. For a supergiant companion star with a 20 R$_{\odot}$ radius, this implies an inclination of the orbital plane in the range of 39$^{\circ}$-57$^{\circ}$, whereas for a main sequence B star as the companion with a 10 R$_{\odot}$ radius, the inclination of the orbital plane is in the range of 60$^{\circ}$-77$^{\circ}$. Pulse profiles created for different energy bands, have complex morphology which shows some energy dependence and increases in pulse fraction with energy. We have also investigated broad-band spectral characteristics, for phase averaged and resolving the pulse phase into peak phase and trough phase. The phase averaged spectrum has a very high N$_{H} (\sim 3 \times 10^{23}$ cm$^{-2}$) and is described by power-law ($\Gamma \sim$ 0.9) with a high energy cut-off above 20 keV. We find a change in the spectral index in the peak phase and trough phase, implying an underlying change in the source spectrum.