SGR 1806-20 about two years after the giant flare: Suzaku, XMM-Newton and INTEGRAL observations

TL;DR

This study presents multi-instrument observations of SGR 1806-20 two years after its giant flare, revealing a near pre-flare flux level, a soft spectrum, and ongoing activity, providing insights into magnetar behavior post-flare.

Contribution

First simultaneous Suzaku, XMM-Newton, and INTEGRAL observations of SGR 1806-20 post-flare, analyzing spectral properties and activity in the context of magnetar models.

Findings

Flux near pre-flare levels

Persistent activity with short bursts

Broad-band spectral analysis supports magnetar theory

Abstract

In December 2004, the soft gamma-ray repeater SGR 1806-20 emitted the most powerful giant flare ever observed. This probably involved a large-scale rearrangement of the magnetosphere leading to observable variations in the properties of its X-ray emission. Here we present the results of the first Suzaku observation of SGR 1806-20, together with almost simultaneous observations with XMM-Newton and INTEGRAL. The source seems to have reached a state characterized by a flux close to the pre-flare level and by a relatively soft spectrum. Despite this, SGR 1806-20 remained quite active also after the giant flare, allowing us to study several short bursts observed by Suzaku in the 1-100 keV range. We discuss the broad-band spectral properties of SGR 1806-20, covering both persistent and bursting emission, in the context of the magnetar model, and consider its recent theoretical developments.