TITLE:   GCN CIRCULAR
NUMBER:  22633
SUBJECT: GRB 180411A: Swift-BAT refined analysis
DATE:    18/04/12 00:51:06 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), Z. Liu (NAOC/U. Leicester),
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-60 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 180411A (trigger #824451)
(Z. Liu, et al., GCN Circ. 22630).  The BAT ground-calculated position is
RA, Dec = 356.840, 66.790 deg, which is 
   RA(J2000)  =  23h 47m 21.6s 
   Dec(J2000) = +66d 47' 25.2" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 97%.
 
The mask-weighted light curve show two major episodes of overlapping peaks
with the first starting at ~T-15 sec, peaking at ~T+5 sec, and second episode
starting at ~T+42 sec, peaking at ~T+52 sec, and returning to zero ~T+180 sec.
T90 (15-350 keV) is 77.5 +- 0.9 sec (estimated error including systematics).
 
The time-averaged spectrum from T-7.02 to T+92.38 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.46 +- 0.03.  The fluence in the 15-150 keV band is 1.2 +- 0.0 x 10^-05 erg/cm2.
The 1-sec peak photon flux measured from T+51.74 sec in the 15-150 keV band
is 6.1 +- 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/824451/BA/