GCN Circular 14862

A. Y. Lien (NASA/GSFC/ORAU), S. D. Barthelmy (GSFC),
W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU), M. Stamatikos (OSU),
J. Tueller (GSFC), T. N. Ukwatta (MSU)
(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 130609B (trigger #557828)
(Krimm, et al., GCN Circ. 13841
Not found
 
 
).  The BAT ground-calculated position is
RA, Dec = 53.776, -40.168 deg which is
     RA(J2000)  =  03h 35m 06.2s
     Dec(J2000) = -40d 10' 04.0"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 43%.

The mask-weighted light curve shows an initial complex of two main
overlapping peaks with numerous subsidiary peaks, with strong emission
between T-10 and T+50 sec and low-level emission between T-30 and T+120 sec.
The highest points are at T+4 and T+18 sec.  Then there is a second, weaker
and softer pair of overlapping peaks between T+160 sec and T+220 sec.  This
second set of peaks is consistent with a flare seen in the Swift-XRT.
T90 (15-350 keV) is 191.98 +- 2.44 sec (estimated error including systematics)
We note that receipt of the full event data for GRB 130609B may reveal
further late-time peaks and require a revision of the T90 estimate.  We will
report on the full data set in a later Circular.

The time-averaged spectrum from T-7.84 to T+213.25 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.23 +- 0.04.  The fluence in the 15-150 keV band is 1.6 +- 0.0 x 10^-05
erg/cm2. The 1-sec peak photon flux measured from T+16.78 sec in the 15-150 keV
band is 8.5 +- 0.4 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/557828/BA/