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GCN Circular 6440

GRB 070521, Swift-BAT refined analysis
2007-05-21T13:29:22Z (17 years ago)
Scott Barthelmy at NASA/GSFC <>
D. Palmer (LANL), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),
C. Guidorzi (Univ Bicocca&INAF-OAB), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), A. Parsons (GSFC), T. Sakamoto (GSFC/ORAU),
G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC)
on behalf of the Swift-BAT team:
Using the data set from T-240 to T+377 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 070521 (trigger #279935)
(Guidorzi, et al., GCN Circ. 6431).  The BAT ground-calculated position is
RA, Dec = 242.659, 30.261 deg  which is 
   RA(J2000)  = 16h 10m 38.1s 
   Dec(J2000) = 30d 15' 37.9" 
with an uncertainty of 1.1 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 47%.
The mask-weighted light curve shows five main peaks the first of which starts
at ~T-10 sec and the last ends at ~T+50 sec.  T90 (15-350 keV) is 37.9 +- 2 sec
(estimated error including systematics).
The time-averaged spectrum from T-14.5 to T+49.7 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.10 +- 0.17, 
and Epeak of 195 +- 123 keV (chi squared 50 for 56 d.o.f.).  
For this model the total fluence in the 15-150 keV band is
8.0 +- 0.2 x 10^-6 erg/cm2 and the 1-sec peak flux measured from
T+30.48 sec in the 15-150 keV band is 6.7 +- 0.3 ph/cm2/sec.  
A fit to a simple power law gives a photon index of 1.38 +- 0.04
(chi squared 58 for 57 d.o.f.).  All the quoted errors are at the 90%
confidence level.
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