TITLE:   GCN CIRCULAR
NUMBER:  30254
SUBJECT: GRB 210618A: Swift-BAT refined analysis
DATE:    21/06/18 20:58:35 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC),  M. G. Bernardini (INAF-OAB),
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-70 to T+960 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210618A (trigger #1056426)
(Bernardini, et al., GCN Circ. 30250).  The BAT ground-calculated position is
RA, Dec = 235.763, 46.072 deg which is 
  RA(J2000)  =  15h 43m 03.2s 
  Dec(J2000) = +46d 04' 17.5" 
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a fairly complex structure between roughly
T-1.5 and T+0.5 seconds.  The spacecraft slewed away from the burst location
starting at around T+320 seconds. T90 (15-350 keV) is 2.13 +- 0.44 sec (estimated 
error including systematics).

The time-averaged spectrum from T-1.42 to T+0.96 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.18 +- 0.28.  The fluence in the 15-150 keV band is 1.8 +- 0.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.50 sec in the 15-150 keV band
is 1.1 +- 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/1056426/BA/