Sub-MeV band observation of a hard burst from AXP 1E 1547.0-5408 with the Suzaku Wide-band All-sky Monitor
Enoto, Teruaki; Yamaoka, Kazutaka; Makishima, Kazuo; Nakagawa, Yujin E.; Ohno, Masanori; Tashiro, Makoto S.; Terada, Yukikatsu; Urata, Yuji; Kouzu, Tomomi; Bamba, Aya; Shibata, Shinpei; Iwakiri, Wataru B.; Yasuda, Tetsuya
Japan, United States, Taiwan
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 160 keV-6.2 MeV 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 0.5-6.2 MeV range, with an averaged 0.16-6.2 MeV flux and extrapolated 25 keV-2 MeV fluence of about 1 × 10-5 erg cm-2 s-1 and about 3 × 10-4 erg cm-2, respectively. After pile-up corrections, the time-resolved WAM spectra of this burst were well-fitted in the 0.16-6.2 MeV 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 cut-off. These results are compared with previous works reporting the persistent emission and weaker short bursts followed by the same outburst.