TITLE:   GCN CIRCULAR
NUMBER:  20999
SUBJECT: GRB 170405A, Swift-BAT refined analysis
DATE:    17/04/07 03:25:45 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

D. M. Palmer (LANL), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), N. Gehrels (GSFC),
H. A. Krimm (NSF/USRA), 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 170405A (trigger #745797)
(Troja et al., GCN Circ. 20984).  The BAT ground-calculated position is
RA, Dec = 219.824, -25.236 deg which is
   RA(J2000)  =  14h 39m 17.8s
   Dec(J2000) = -25d 14' 09.7"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 6%.

The burst was outside of the BAT calibrated field of view from T-134.3 s to T+56.7 s.
The mask-weighted light curve using the “detection mask” (which covers a broader
field of view, but is not well calibrated; see detail description in Markwardt et al. 2007)
shows a multi-peaked structure that starts at ~T-30 s and ends at ~T+240 s. The
major peak occurs at ~T+5 s. T90 (15-350 keV) is 164.7 +- 35.4 sec (estimated error
including systematics).

The time-averaged spectrum from T+56.7 to T+242.5 sec (i.e., when the burst is in the
BAT calibrated field of view) is best fit by a simple power-law model.  The power law
index of the time-averaged spectrum is 1.59 +- 0.12.  The fluence in the 15-150 keV
band is 3.7 +- 0.3 x 10^-06 erg/cm2. 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/745797/BA/