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GCN Circular 7462

Subject
GRB 080319B, Swift-BAT refined analysis
Date
2008-03-19T20:21:44Z (16 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
J. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), E. Fenimore (LANL),
N. Gehrels (GSFC), H. Krimm (GSFC/USRA), C. Markwardt (GSFC/UMD),
K. McLean (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC),
J. L. Racusin (PSU), T. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-120 to T+182 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 080319B (trigger #306757)
(Racusin, et al., GCN Circ. 7427).  The BAT ground-calculated position is
RA, Dec = 217.919, 36.300 deg which is 
   RA(J2000)  =  14h 31m 40.7s 
   Dec(J2000) = +36d 17' 58.4" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
 
The mask-weighted light curve shows a large long bump of a peak
starting at ~T-10 sec, ramping up until ~T+10 sec, then mostly a flat top
with some small structure superposed, then starting to decay at ~T+50 sec.
It returns nearly to background by ~T+64 sec at which point there is
a loss of data due to an on-board data product buffer overflow.
The data resumes at T+120 sec.  There is still detectable emission
in the BAT 15-350 keV band out to T+180 sec (the limit of the data
downlinked so far).  From other count rate data products, we can say
that there is no other peaks during the 60-sec missing event data window
and that the low-level emission is about 10-15% of the peak emission.
Given the missing data, T90 (15-350 keV) has to be >50 sec
(estimated error including systematics).
 
The time-averaged spectrum from T-3.8 to T+62.2 and T+120 to T+151 sec
is fit by a simple power-law model.  The power law index
of the time-averaged spectrum is 1.04 +- 0.02.  The fluence
in the 15-150 keV band is 8.1 +- 0.1 x 10^-05 erg/cm2.
The 1-sec peak photon flux measured from T+16.87 sec in the 15-150 keV band
is 24.8 +- 0.5 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 
 
The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/306757/BA/

Due to a large backlog in downlinking the full data on this burst,
we currently do not have the usual data set out to long times yet.
Should the remaining data show that there is ongoing activity 
for this burst past the data cutoff at T+182sec, then we will
issue an updated 'refined analysis' circular.
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