The very-faint X-ray binary IGR J17062-6143: a truncated disk, no pulsations and a possible outflow

TL;DR

This study investigates the faint neutron star X-ray binary IGR J17062-6143, revealing a truncated accretion disk, possible outflows, and no pulsations, providing insights into its low luminosity accretion behavior.

Contribution

It provides the first detailed analysis combining relativistic reflection, high-resolution spectroscopy, and pulsation searches for this source, highlighting the accretion geometry and outflow evidence.

Findings

Disk truncated at ~164 km from neutron star

Evidence for oxygen-rich outflowing material

No detection of millisecond pulsations

Abstract

We present a comprehensive X-ray study of the neutron star low-mass X-ray binary IGR J17062-6143, which has been accreting at low luminosities since its discovery in $2006$. Analysing NuSTAR, XMM-Newton and Swift observations, we investigate the very faint nature of this source through three approaches: modelling the relativistic reflection spectrum to constrain the accretion geometry, performing high-resolution X-ray spectroscopy to search for an outflow, and searching for the recently reported millisecond X-ray pulsations. We find a strongly truncated accretion disk at $77^{+22}_{-18}$ gravitational radii ($\sim 164$ km) assuming a high inclination, although a low inclination and a disk extending to the neutron star cannot be excluded. The high-resolution spectroscopy reveals evidence for oxygen-rich circumbinary material, possibly resulting from a blueshifted, collisionally-ionised outflow. Finally, we do not detect any pulsations. We discuss these results in the broader context of possible explanations for the persistent faint nature of weakly accreting neutron stars. The results are consistent with both an ultra-compact binary orbit and a magnetically truncated accretion flow, although both cannot be unambigiously inferred. We also discuss the nature of the donor star and conclude that it is likely a CO or O-Ne-Mg white dwarf, consistent with recent multi-wavelength modelling.