The First X-Ray Polarimetry of an Eclipsing Low-Mass X-Ray Binary: Serendipitous IXPE Observation of AX J1745.6-2901

TL;DR

This study reports the first X-ray polarization measurement of the low-mass X-ray binary AX J1745.6-2901, revealing polarization characteristics that suggest scattering processes like disk winds.

Contribution

First X-ray polarimetric measurement of AX J1745.6-2901, demonstrating polarization variability and providing insights into scattering mechanisms in the system.

Findings

Polarization degree of 14.7% ± 4.0% detected.

Polarization increases to 34.2% during eclipse.

Scattering mechanisms likely from disk winds.

Abstract

We present the first X-ray polarimetric measurement of the neutron star low-mass X-ray binary system AX J1745.6-2901 conducted by the Imaging X-ray Polarimetry Explorer (IXPE) satellite. This transient source, located within $ \sim $1.5' of the Galactic center, was observed serendipitously during a MAXI J1744-294 observation with a duration of 150 ks. The complex nature of the region in which AX J1745.6-2901 is located poses a challenge for studying its polarization. By performing a detailed analysis of the contamination from MAXI J1744-294 and the Galactic center diffuse emission, we find the source polarization degree PD = 14.7$\% \pm$ 4.0$\%$ and polarization angle PA = 122$^\circ \pm 8^\circ$. The phase-resolved analysis shows increase in polarization during the eclipse phase, with PD = 34.2$\% \pm$ 8.7$\%$, suggesting that the polarization-inducing mechanisms are of scattering nature, probably originating from disk winds.