[vsnet-grb-info 19183] GRB 170307A (trigger 741528): Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  20838
SUBJECT: GRB 170307A (trigger 741528): Swift-BAT refined analysis
DATE:    17/03/08 13:59:24 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien at nasa.gov>

M. Stamatikos (OSU), 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), D. M. Palmer (LANL),
T. Sakamoto (AGU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-12 to T+963 sec from the recent telemetry downlink,
we determine that BAT trigger #741528 (Lien et al., GCN Circ. 20832) is indeed
a GRB, which also detected by Fermi GBM (Hui et al., GCN Circ. 20835). We report
further analysis of BAT GRB 170307A (trigger #741528).
The BAT ground-calculated position is
RA, Dec = 13.510, 9.538 deg which is
   RA(J2000)  =  00h 54m 02.5s
   Dec(J2000) = +09d 32' 17.9"
with an uncertainty of 2.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 43%.

The mask-weighted light curve shows a weak structure with several overlapping
pulses that starts at ~T+55 s and ends at ~T+125 s. The burst emission might
start before it came into the BAT FOV at ~T-12 s. T90 (15-350 keV) is
56.92 +- 27.40 sec (estimated error including systematics).

The time-averaged spectrum from T+55.33 to T+124.69 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.88 +- 0.23.  The fluence in the 15-150 keV band is 1.3 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+69.72 sec in the 15-150 keV band
is 1.4 +- 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/741528/BA/