S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC),
E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
A. Y. Lien (NASA/GSFC/ORAU), C. B. Markwardt (GSFC), A. Maselli (INAF-IASFPA),
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-60 to T+243 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 130427B (trigger #554635)
(Maelli, et al., GCN Circ. 14460). The BAT ground-calculated position is
RA, Dec = 314.900, -22.548 deg, which is
RA(J2000) = 20h 59m 36.0s
Dec(J2000) = -22d 32' 51.6"
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 22%.
The mask-weighted light curve shows shows a very small peak at ~T-3 sec,
the main peak starting at ~T-1 sec, peaking at ~T+2 sec, and ending at
~T+40 sec. T90 (15-350 keV) is 27.0 +- 7.3 sec (estimated error
The time-averaged spectrum from T-1.29 to T+32.71 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.64 +- 0.15. The fluence in the 15-150 keV band is 1.5 +- 0.1 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+0.71 sec in the 15-150 keV band
is 3.0 +- 0.4 ph/cm2/sec. All the quoted errors are at the 90% confidence
The results of the batgrbproduct analysis are available at