Searching for small-scale diffuse emission around SGR 1806-20

TL;DR

This study investigates the presence of small-scale diffuse X-ray emission around SGR 1806-20 using Chandra observations, finding no significant extended emission and confirming its point-like nature in X-rays.

Contribution

The paper provides the first detailed analysis of small-scale X-ray emission around SGR 1806-20 post-flare, using careful PSF comparison to rule out extended emission.

Findings

No statistically significant extended X-ray emission detected.

SGR 1806-20 appears point-like in X-rays both after flare and during quiescence.

Results constrain models of diffuse emission around magnetars.

Abstract

Diffuse radio emission was detected around the soft gamma-ray repeater SGR 1806-20, after its 2004 powerful giant flare. We study the possible extended X-ray emission at small scales around SGR 1806-20, in two observations by the High Resolution Camera Spectrometer (HRC-S) on board of the Chandra X-ray Observatory: in 2005, 115 days after the giant flare, and in 2013, during quiescence. We compare the radial profiles extracted from data images and PSF simulations, carefully considering various issues related with the uncertain calibration of the HRC PSF at sub-arcsecond scales. We do not see statistically significant excesses pointing to an extended emission on scales of arcseconds. As a consequence, SGR 1806-20 is compatible with being point-like in X-rays, months after the giant flare, as well as in quiescence.