[vsnet-grb-info 4846] GRB 070616: Suzaku/WAM observation of the prompt emission

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6578
SUBJECT: GRB 070616: Suzaku/WAM observation of the prompt emission
DATE:    07/06/26 07:51:35 GMT
FROM:    Makoto Tashiro at Saitama U/Swift  <tashiro at phy.saitama-u.ac.jp>

K. Morigami, N. Kodaka, K. Onda, M. Tashiro, M. Suzuki, Y. Urata,
A. Endo (Saitama U.), T. Uehara, M. Ohno, T. Takahashi, Y. Fukazawa,
C. Kira (Hiroshima U.), T. Enoto, R. Miyawaki, K. Nakazawa,
K. Makishima (Univ. of Tokyo), K. Yamaoka, Y. E. Nakagawa,
S. Sugita (Aoyama Gakuin U.), T. Tamagawa, Y. Terada (RIKEN),
S. Hong (Nihon U.), M. Kokubun, M. Suzuki, T. Takahashi (ISAS/JAXA),
E. Sonoda, M.Yamauchi, S. Maeno, H. Tanaka, R. Hara (Univ. of Miyazaki),
and Suzaku WAM team report:

The long burst, GRB 070616 (Swift/BAT trigger #282445; Starling et al.,
GCN circ 6542; Sakamoto et al., GCN circ 6543; Starling et al., GCN
Report 66.2) triggered the Suzaku Wide-band All-sky Monitor (WAM)
covering 50 keV to 5 MeV at 16:31:50 UT (T0), which was 137 second
after the Swift/BAT trigger time. Since The WAM BST mode data did not
cover the Swift/BAT trigger time, we employed continuous monitoring
(TRN) data to evaluate the whole light curve and the averaged spectrum
of the burst. The observed light curve exhibits multiple peaked
structures preceded by a precursor-like emission (from T0-163 to T0-158 
seconds). Although Starling et al. reported a very long duration, over 
600 seconds (GCN Report 66.1), the Suzaku/WAM covered only 140 seconds 
from the start of the main peaks before the entry of the SAA region in 
the orbit.

The derived fluence in 100-1000 keV was more than
6.6 (-0.6, +0.7) x 10^-6 erg/cm^2. The 1-s peak flux was
1.40 (-0.17,+0.16) photons/cm^2/s in the same energy range.

Preliminary result shows that the time-averaged spectrum from T0-10 to
T0+30 seconds is well fitted with a single power-law of a photon
index Gamma = 2.36 (-0.12, +0.12) in the 100-1000 keV energy range.

All the quoted errors are at statistical 90% confidence level, while
the systematic errors are not considered.

The light curve data for this burst is available at the following web site.

http://www.astro.isas.ac.jp/suzaku/HXD-WAM/WAM-GRB/grb/trig/grb_table.html