GCN Circular 16306

T. N. Ukwatta (MSU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (NASA/UMBC), C. B. Markwardt (GSFC), A. Melandri (INAF-OAB),
D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU),
J. Tueller (GSFC) (i.e. the Swift-BAT team):

Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 140518A (trigger #599287)
(Melandri, et al., GCN Circ. 16298
Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 227.231, 42.396 deg which is
  RA(J2000)  =  15h 08m 55.3s
  Dec(J2000) = +42d 23' 44.2"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 89%.

The mask-weighted light curve shows multiple peaks with roughly three main pulse
structures. The first main pulse starts at ~T-4 s and ends at ~T+8 s. The second main
pulse starts at ~T+38 s, followed immediately by the third main pulse structure that
starts at ~T+48 s and ends at ~T+61 s. Additionally, each of these main pulse structure
contains several  sub-pulses. T90 (15-350 keV) is 60.5 +- 2.4 sec (estimated error
including systematics).

The time-averaged spectrum from T-4.1 to T+60.0 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.92 +- 0.61,
and Epeak of 43.9 +- 7.6 keV (chi squared 54.15 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 1.0 +- 0.1 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+41.94 sec in the 15-150 keV band is
1.0 +- 0.1 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.97 +- 0.13 (chi squared 65.02 for 57 d.o.f.).  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/599287/BA/