The 2009 outburst of magnetar 1E 1547-5408: Persistent radiative and burst properties

TL;DR

This paper analyzes the 2009 outburst of magnetar 1E 1547-5408, revealing significant flux increase, spectral hardening, and detailed burst properties, providing insights into magnetar behavior during outbursts.

Contribution

It presents a comprehensive analysis of the persistent and burst emission properties during the 2009 outburst, including correlations and phase relationships, expanding understanding of magnetar outburst phenomena.

Findings

Flux increased by a factor of ~500 and hardened significantly.

Burst peaks occur randomly in phase, with misaligned pulse components.

A correlation exists between burst hardness and flux.

Abstract

The magnetar 1E~1547$-$5408 recently exhibited two periods of outburst, beginning on 2008 October 3 and 2009 January 22. Here we present an analysis of the persistent radiative evolution and a statistical study of the burst properties during the 2009 outburst using the {\em Swift} X-ray Telescope (XRT). We find that the 1--10 keV flux increased by a factor of $\sim500$ and hardened significantly, peaking $\sim6$ hours after the onset of the outburst. The observed pulsed fraction exhibited an anti-correlation with phase-averaged flux. Properties of the several hundred X-ray bursts during the 2009 outburst were determined and compared to those from other magnetar outburst events. We find that the peaks of the bursts occur randomly in phase but that the folded counts that compose the bursts exhibit a pulse which is misaligned with the persistent pulse phase. We also report a correlation between burst hardness and flux. We compare the hardness-flux evolution of the persistent emission of both outbursts to those from other magnetars and find that although there does exist an overall trend, the degree of hardening for a given increase in flux is not uniform from source to source. These results are discussed in the context of previous results and within the magnetar model.