TITLE:   GCN CIRCULAR
NUMBER:  29251
SUBJECT: GRB 210104A: Swift-BAT refined analysis
DATE:    21/01/05 02:33:46 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

D. M. Palmer (LANL), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
T. Sakamoto (AGU), M. Stamatikos (OSU),
E. Troja (NASA/GSFC/UMCP), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-239 to T+963 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 210104A (trigger #1015873)
(Troja et al., GCN Circ. 29233).  The BAT ground-calculated position is
RA, Dec = 103.771, 64.675 deg which is
   RA(J2000)  =  06h 55m 04.9s
   Dec(J2000) = +64d 40' 30.6"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 82%.

The mask-weighted light curve shows a multi-peaked structure that
starts at ~T-1 s and ends at ~T+45 s. Several prominent peaks occur
at ~T+4 s, ~T+21 s, ~T+27 s, and ~T+34 s, respectively. T90 (15-350 keV)
is 32.06 +- 0.49 sec (estimated error including systematics).

The time-averaged spectrum from T-1.00 to T+45.39 sec is best fit by
a simple power-law model.  The power law index of the time-averaged
spectrum is 1.55 +- 0.04.  The fluence in the 15-150 keV band is
8.8 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from
T+26.78 sec in the 15-150 keV band is 12.1 +- 0.4 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/1015873/BA/