Sub-MeV Band Observation of a Hard Burst from AXP 1E 1547.0-5408 with the Suzaku Wide-band All-sky Monitor

TL;DR

This paper reports on the detection and analysis of a bright sub-MeV burst from AXP 1E 1547.0-5408 using Suzaku's wide-band all-sky monitor, revealing detailed spectral properties and contributing to understanding magnetar burst emissions.

Contribution

First detailed spectral analysis of a sub-MeV burst from AXP 1E 1547.0-5408 using Suzaku WAM data, highlighting two-component spectral models for such bursts.

Findings

Detected at least 254 bursts from the source during the outburst

The brightest burst's fluence was about 3x10^-4 erg cm^-2 in 25 keV-2 MeV range

Spectral fits favored blackbody plus thermal bremsstrahlung or cutoff power-law models

Abstract

The 2.1-s anomalous X-ray pulsar 1E 1547.0-5408 exhibited an X-ray outburst on 2009 January 22, emitting a large number of short bursts. The wide-band all- sky monitor (WAM) on-board Suzaku detected at least 254 bursts in the 160keV-6.2MeV band over the period of January 22 00:57-17:02 UT from the direction of 1E 1547.0-5408. One of these bursts, which occurred at 06:45:13, produced the brightest fluence in the 0.5-6.2MeV range, with an averaged 0.16-6.2MeV flux and extrapolated 25 keV-2 MeV fluence of about 3x10-6 erg cm-2 s-1 and about 3x10-4 erg cm-2, respectively. After pile-up corrections, the time-resolved WAM spectra of this burst were well-fitted in the 0.16-6.2MeV range by two-component models; specifically, a blackbody plus an optically thin thermal bremsstrahlung or a combination of a blackbody and a power-law component with an exponential cutoff. These results are compared with previous works reporting the persistent emission and weaker short bursts followed by the same outburst.