TITLE:   GCN CIRCULAR
NUMBER:  14718
SUBJECT: GRB 130528A: Swift-BAT refined analysis
DATE:    13/05/29 11:38:26 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@lheamail.gsfc.nasa.gov>

J. R. Cummings (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
V. D'Elia (ASDC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU), G. Sato (ISAS),
M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (MSU)
(i.e. the Swift-BAT team):
 
Using the data set from T-61 to T+243 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 130528A (trigger #556870)
(D'Elia, et al., GCN Circ. 14711).  The BAT ground-calculated position is
RA, Dec = 139.405, 87.300 deg, which is 
   RA(J2000)  =  09h 17m 37.2s 
   Dec(J2000) = +87d 18' 01.5" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.
 
The mask-weighted light curve shows several overlapping peaks starting
at ~T+0, peaking at ~T+4 sec, and ending at ~T+80 sec.
T90 (15-350 keV) is 59.4 +- 3.6 sec (estimated error including systematics).
 
The time-averaged spectrum from T+0.12 to T+79.34 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.39 +- 0.19, 
and Epeak of 118.3 +- 79.7 keV (chi squared 42.3 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 5.1 +- 0.2 x 10^-6 erg/cm2
and the 1-sec peak flux measured from T+6.06 sec in the 15-150 keV band is
3.0 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.67 +- 0.05 (chi squared 48.6 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/556870/BA/