The nature of the absorber in the INTEGRAL highly obscured sgHMXB IGR J17252-3616

TL;DR

This study uses X-ray observations to map the complex, asymmetric stellar wind structures around the obscured sgHMXB IGR J17252-3616, revealing new insights into the wind's geometry and high obscuration sources.

Contribution

First imaging of dynamical wind structures in a sgHMXB, combining timing and spectral analysis to understand wind asymmetry and obscuration.

Findings

Detected highly asymmetric stellar wind extending 2-3 stellar radii.

Identified three wind components: unperturbed wind, asymmetric tail, and material cusp.

Revealed wind structures explain high obscuration in the system.

Abstract

INTEGRAL played a key role in discovering obscured sgHMXB in the Galaxy. We used XMM-Newton to perform X-ray wind tomography of a specific of these systems, IGR J17252-3616, featuring eclipses of the accreting pulsar. The X-ray band (0.2-10 keV) reveals vital information on the geometry of the surrounding gas probing simultaneously the absorption and the fluorescence emission. The XMM observations were scheduled to cover as many orbital phases as possible. Timing analysis allows the derivation of an accurate orbital solution and of the system parameters. Spectral analysis revealed remarkable variations of the absorbing column density along the orbit and of the Fe K$\alpha$ fluorescence line around the eclipse. The combination of these observables revealed a highly asymmetric and unprecedentedly extended structure in the stellar wind extending up to 2-3 stellar radii. The observations can be modeled in terms of three independent components: i) the unperturbed stellar wind ii) the contribution of a highly asymmetric hydrodynamic wind tail-like structure and iii) a cusp of material close to the neutron star. These dynamical structures are imaged for the first time in a sgHMXB and explain the source of the high obscuration.