GCN Circular 5516
Subject
GRB 060904A: Refined analysis of the Swift-BAT burst
Date
2006-09-04T12:33:22Z (18 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
H. Krimm (GSFC/USRA), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/UMD), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Grupe (PSU), D. Hullinger (BYU-Idaho), 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)
on behalf of the Swift-BAT team:
Using the data set from T-110 to T+843 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 060904 (trigger #227996)
(Grupe, et al., GCN Circ. 5502). The BAT ground-calculated position
is (RA,Dec) = 237.730, 44.984 deg {15h 50m 55.3s, 44d 59' 3.7"} (J2000)
+- 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 94%.
The mask-weighted lightcurve shows the emission starting at a very low level
at ~T-70 sec, then increasing slightly at ~T-7 sec for the trigger with several
small peaks until the main peak. The main emission peak starts at T+45,
peaking at T+56, and ending at ~T+125 sec. T90 (15-350 keV) is 80 +- 2 sec
(estimated error including systematics). Note that the spacecraft slewed
to the field of view containing the burst approximately 110 seconds
before the trigger, so there is no BAT data before this time.
The time-averaged spectrum from T-23.9 to T+108.7 is best fit by
a simple power-law model. The power law index of the time-averaged spectrum
is 1.52 +- 0.04. The fluence in the 15-150 keV band is 7.9 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+55.34 sec in the 15-150 keV
band is 4.9 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90%
confidence level.