[vsnet-grb-info 5104] GRB 070911: Swift/BAT and Suzaku/WAM joint spectral analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6810
SUBJECT: GRB 070911: Swift/BAT and Suzaku/WAM joint spectral analysis
DATE:    07/09/21 13:14:44 GMT
FROM:    Takanori Sakamoto at NASA/GSFC  <takanori at milkyway.gsfc.nasa.gov>

L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC),
T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. Ukwatta (GWU)
on behalf of the Swift-BAT team,

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

report:

We performed the Swift/BAT, and Suzaku/WAM joint fit spectral
analysis of GRB 070911 (Swift-BAT trigger #290624; Krimm, et al.,
GCN Circ. 6777).  The time interval of the spectral data for each
instrument is chosen from T0(WAM)-56 to T0(WAM)+149 sec where
T0(WAM) is the trigger time of WAM at 05:58:20.069 UTC.
The energy ranges which we used in the joint spectral analysis
are 14-150 keV and 100-1000 keV for Swift/BAT and Suzaku/WAM
respectively.  The spectral data of two instruments are fit
with the spectral model multiplied by the constant factor to
take into account the systematic uncertainties in the response
matrices of each instrument.

The spectrum is well fit with a power-law with exponential cutoff
model (dN/dE ~ E^{alpha} * exp(-(2+alpha)*E/Epeak)).  The constant
factors of each instrument agree within 10%.  No systematic residual
from the best fit model is seen in the spectral data of each instrument.
The best fit spectral parameters are: alpha = -1.6 +- 0.1 and
Epeak = 170 (-50/+280) keV (chi2/dof = 59/74).  The energy fluence
in the 15-1000 keV band calculated by a power-law with exponential
cutoff model for this 205 sec interval is 2.1 (-0.2/+0.4) x 10^-5 erg/cm2
(assuming the constant factor of the BAT is fixed to 1).

All the quoted errors are at the 90% confidence level.