Confirmation of the Supergiant Fast X-ray Transient nature of AX J1841.0-0536 from Swift outburst observations

TL;DR

This study confirms AX J1841.0-0536 as a supergiant fast X-ray transient through Swift observations, revealing characteristic spectral and temporal properties consistent with the class, and compares it to a prototype SFXT.

Contribution

First broad-band spectral analysis of AX J1841.0-0536 down to 0.3 keV, confirming its classification as an SFXT based on detailed observational properties.

Findings

X-ray light curve shows typical SFXT flare and decay pattern

Spectral properties resemble those of known SFXTs like IGR J17544-2619

Large dynamical range in X-ray luminosity supports SFXT classification

Abstract

Swift observed an outburst from the supergiant fast X-ray transients (SFXT) AX J1841.0-0536 on 2010 June 5, and followed it with XRT for 11 days. The X-ray light curve shows an initial flare followed by a decay and subsequent increase, as often seen in other SFXTs, and a dynamical range of ~1600. Our observations allow us to analyse the simultaneous broad-band (0.3-100 keV) spectrum of this source, for the first time down to 0.3 keV, can be fitted well with models usually adopted to describe the emission from accreting neutron stars in high-mass X-ray binaries, and is characterized by a high absorption (N_H~2x10^22 cm-2), a flat power law (Gamma~0.2), and a high energy cutoff. All of these properties resemble those of the prototype of the class, IGR J17544-2619, which underwent an outburst on 2010 March 4, whose observations we also discuss. We show how well AX J1841.0-0536 fits in the SFXT class, based on its observed properties during the 2010 outburst, its large dynamical range in X-ray luminosity, the similarity of the light curve (length and shape) to those of the other SFXTs observed by Swift, and the X-ray broad-band spectral properties.