T. N. Ukwatta (MSU), 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), C. B. Markwardt (GSFC), F. E. Marshall (NASA/GSFC),
D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (OSU), J. Tueller (GSFC)
(i.e. the Swift-BAT team):
Using the data set from T-120 to T+258 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 120311B (trigger #517489)
(Marshall, et al., GCN Circ. 13038). The BAT ground-calculated position is
RA, Dec = 258.551, -13.068 deg, which is
RA(J2000) = 17h 14m 12.2s
Dec(J2000) = -13d 04' 05.0"
with an uncertainty of 1.3 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 62%.
The mask-weighted light curve shows two nearly separated peaks, the first
starting at ~T-15 sec, peaking at ~T_0, and the minimum between the two
peaks is at ~T+5 sec. The second peak peaks at ~T+10 sec, and
returns to baseline at ~T+22 sec. T90 (15-350 keV) is 28.2 +- 5.5 sec
(estimated error including systematics).
The time-averaged spectrum from T-13.88 to T+21.63 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.96 +- 0.14. The fluence in the 15-150 keV band is 1.0 +- 0.1 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+9.04 sec in the 15-150 keV band
is 1.5 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence
The results of the batgrbproduct analysis are available at