TITLE:   GCN CIRCULAR
NUMBER:  6354
SUBJECT: GRB 070427, Swift-BAT Refined Analysis
DATE:    07/04/27 18:56:04 GMT
FROM:    Michael Stamatikos at GSFC  <michael@milkyway.gsfc.nasa.gov>

G. Sato (GSFC/ISAS), 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), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC) on behalf of the
Swift-BAT team:
 
Using the data set from T-240 to T+962 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 070427
(trigger #277356)  (Sato, et al., GCN Circ. 6352).  The BAT
ground-calculated position is RA, Dec = 28.871, -27.603 deg which is 
   RA(J2000) = 1h 55m 29.1s 
   Dec(J2000) = -27d 36' 11.2" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The
partial coding was 100%.
 
The mask weighted light curve steeply rises at ~ T+0 sec, exhibiting some
multi-peak sub structure, falling more gradually until ~T+20 sec, with
trivial emission above 100 keV. T90 (15-350 keV) is 11 +- 1 sec (estimated
error including systematics).
 
The time-averaged spectrum from T-0.2 to T+13.7 is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is 2.08
+- 0.10. The fluence in the 15-150 keV band is 7.2 +- 0.4 x 10^-07 erg/cm^2.
The 1-sec peak photon flux measured from T+6.79 sec in the 15-150 keV band
is 1.3 +- 0.1 ph/cm^2/sec.  All the quoted errors are at the 90%
confidence level.