# The Chandra Dust Scattering Halo of Galactic Center transient Swift J174540.7-290015

## TL;DR

This paper reports the detection and analysis of a dust scattering halo around the Galactic Center transient Swift J174540.7-290015, revealing insights into the source's behavior and the intervening dust properties.

## Contribution

It presents the first detection of a dust scattering halo around this transient and analyzes its evolution, linking it to the source's spectral state changes.

## Key findings

- Detection of a dust scattering halo consistent with X-ray scattering by foreground dust.
- Evidence of the source transitioning from a soft to hard spectral state.
- The source is likely a low mass X-ray binary in the Galactic Center.

## Abstract

We report the detection of a dust scattering halo around a recently discovered X-ray transient, Swift J174540.7-290015, which in early February of 2016 underwent one of the brightest outbursts (F_X ~ 5e-10 erg/cm^2/s) observed from a compact object in the Galactic Center field. We analyze four Chandra images that were taken as follow-up observations to Swift discoveries of new Galactic Center transients. After adjusting our spectral extraction for the effects of detector pileup, we construct a point spread function for each observation and compare it to the GC field before the outburst. We find residual surface brightness around Swift J174540.7-290015, which has a shape and temporal evolution consistent with the behavior expected from X-rays scattered by foreground dust. We examine the spectral properties of the source, which shows evidence that the object transitioned from a soft to hard spectral state as it faded below L_X ~ 1e36 erg/s. This behavior is consistent with the hypothesis that the object is a low mass X-ray binary in the Galactic Center.