[vsnet-grb-info 3176] GRB 060427: Refined analysis of the Swift-BAT burst

[GCN Circulars]

TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  5011
SUBJECT: GRB 060427:  Refined analysis of the Swift-BAT burst
DATE:    06/04/27 21:21:57 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <Scott at lheamail.gsfc.nasa.gov>

H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. Barthelmy (GSFC),
J. Cummings (GSFC/NRC), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (BYU-Idaho), V. Mangano  (INAF-IASFPA), C. Markwardt (GSFC/UMD), 
D. Palmer (LANL), A. Parsons (GSFC), T. Sakamoto (GSFC/NRC),
G. Sato (ISAS), J. Tueller (GSFC)
on behalf of the Swift-BAT team:

Using the data set from T-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 060427 (trigger #207281)
(Mangano, et al., GCN 5006).  The BAT ground-calculated position is RA,Dec =
124.175,+62.654 deg {8h 16m 42.0s,+62d 39' 13.4"} (J2000) +- 2.1 arcmin,
(radius, sys+stat, 90% containment).  The partial coding was 71%.

The mask-weighted lightcurve shows a broad peak starting at ~T-20 sec
and lasting to ~T+80 sec.  T90 (15-350 keV) is 64 +- 5 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-10.0 to T+60.0 is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.87 +- 0.29.  The fluence in the 15-150 keV band is
5.0 +- 0.9 x 10^-07 erg/cm2.  The 1-sec peak photon flux measured
from T+5.00 sec in the 15-150 keV band is 0.3 +- 0.1 ph/cm2/sec.
All the quoted errors are at the 90% confidence level.