# IGR J17503-2636: a candidate supergiant fast X-ray transient

## TL;DR

IGR J17503-2636 is a newly identified supergiant fast X-ray transient exhibiting fast variability, a broad spectral feature possibly indicating a magnetized neutron star, and is associated with a highly reddened OB supergiant at about 10 kpc.

## Contribution

This study presents the first detailed analysis of IGR J17503-2636, identifying it as a candidate supergiant fast X-ray transient with potential magnetic neutron star characteristics.

## Key findings

- Fast X-ray variability observed
- Spectral feature suggests a magnetized neutron star
- Likely associated with a reddened OB supergiant at ~10 kpc

## Abstract

IGR J17503-2636 is a hard X-ray transient discovered by INTEGRAL on 2018 August 11. This was the first ever reported X-ray emission from this source. Following the discovery, follow-up observations were carried out with Swift, Chandra, NICER, and NuSTAR. We report in this paper the analysis and results obtained from all these X-ray data. Based on the fast variability in the X-ray domain, the spectral energy distribution in the 0.5-80 keV energy range, and the reported association with a highly reddened OB supergiant at ~10 kpc, we conclude that IGR J17503-2636 is most likely a relatively faint new member of the supergiant fast X-ray transients. Spectral analysis of the NuSTAR data revealed a broad feature in addition to the typical power-law with exponential roll-over at high energy. This can be modeled either in emission or as a cyclotron scattering feature in absorption. If confirmed by future observations, this feature would indicate that IGR J17503-2636 hosts a strongly magnetized neutron star with B~2e12 G.