TITLE:   GCN CIRCULAR
NUMBER:  29479
SUBJECT: GRB 210209A: Swift-BAT refined analysis
DATE:    21/02/11 16:37:16 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

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

Using the data set from T-239 to T+800 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210209A (trigger #1031636)
(Laha, et al., GCN Circ. 29442).  The BAT ground-calculated position is
RA, Dec = 328.097, 43.545 deg which is 
  RA(J2000)  =  21h 52m 23.3s 
  Dec(J2000) = +43d 32' 40.4" 
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 96%.

The mask-weighted light curve shows a  double-peaked structure running from
roughly T-35 sec to T+140 seconds.  The two peaks were at T+3 sec and T+65 sec.
T90 (15-350 keV) is 139.4 +- 21.5 sec (estimated error including systematics).

The time-averaged spectrum from T-40.34 to T+134.72 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.52 +- 0.12.  The fluence in the 15-150 keV band is 2.4 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+2.68 sec in the 15-150 keV band
is 0.6 +- 0.2 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/1031636/BA/