Temporal and spectral evolution in X- and gamma-rays of magnetar 1E 1547.0-5408 since its October 2008 outburst: the discovery of a transient hard pulsed component after its January 2009 outburst
Publication date: 01 Apr 2012
Authors: Kuiper, L., Hermsen, W., den Hartog, P.R., Urame, J.O.
Journal: The Astrophysical Journal
Copyright: IOP Publishing 2012The magnetar 1E1547.0-5408 exhibited outbursts in October 2008 and January 2009. In this paper we present in great detail the evolution of the temporal and spectral characteristics of the persistent total and pulsed emission of 1E1547.0-5408 between <1 and 300 keV starting in October 3, 2008, and ending in January 2011. We analyzed data collected with the Rossi X-ray Timing Explorer, the International Gamma-Ray Astrophysics Laboratory and the Swift satellite. We report the evolution of the pulse frequency, and the measurement at the time of the onset of the January 2009 outburst of an insignificant jump in frequency, but a major frequency derivative jump. Before this glitch, a single broad pulse is detected, mainly for energies below ~10 keV. Surprisingly, ~11 days after the glitch a new transient high-energy (up to ~150 keV) pulse appears with a Gaussian shape and width 0.23, shifted in phase by ~0.31 compared to the low-energy pulse, which smoothly fades to undetectable levels in ~350 days. We report the evolution of the pulsed-emission spectra. For energies 2.5-10 keV all pulsed spectra are very soft with photon indices between -4.6 and -3.9. For ~10-150 keV, after the glitch, we report hard non-thermal pulsed spectra, similar to what has been reported for the persistent pulsed emission of some anomalous X-ray pulsars. This pulsed hard X-ray emission reached maximal luminosity 70 ± 30 days after the glitch epoch, followed by a gradual decrease by more than a factor of 10 over ~300 days. These characteristics differ from those of the total emission.
[Abstract abbreviated due to character limitations.]
We discuss these findings in the framework of the magnetar model.