TITLE:   GCN CIRCULAR
NUMBER:  29672
SUBJECT: GRB 210318A: Swift-BAT refined analysis
DATE:    21/03/19 12:04:17 GMT
FROM:    Hans Krimm at NSF/NASA-GSFC  <hkrimm@nsf.gov>

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

Using the data set from T-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210318A (trigger #1037339)
(Troja, et al., GCN Circ. 29662).  The BAT ground-calculated position is
RA, Dec = 33.892, -37.755 deg which is 
  RA(J2000)  =  02h 15m 34.0s 
  Dec(J2000) = -37d 45' 17.7" 
with an uncertainty of 2.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 75%.

The mask-weighted light curves shows a single broad FRED-shaped peak with
some structure.  The emission starts at ~T10 sec, peaks at T+5 sec, and 
falls to background by T+50 sec.  T90 (15-350 keV) is 48.00 +- 22.63 sec 
(estimated error including systematics).

The time-averaged spectrum from T-12.37 to T+35.63 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.48 +- 0.33.  The fluence in the 15-150 keV band is 6.4 +- 1.3 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T+11.13 sec in the 15-150 keV band
is 0.3 +- 0.3 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/1037339/BA/