Skip to main content
Testing. You are viewing the public testing version of GCN. For the production version, go to
New Announcement Feature, Code of Conduct, Circular Revisions. See news and announcements

GCN Circular 14470

GRB 130427A: Swift-BAT refined analysis
2013-04-27T19:33:00Z (11 years ago)
Scott Barthelmy at NASA/GSFC <>
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 130427A (trigger #554620)
(Maselli, et al., GCN Circ. 14448).  The BAT ground-calculated position is
RA, Dec = 173.150, 27.706 deg which is 
   RA(J2000)  =  11h 32m 36.1s 
   Dec(J2000) = +27d 42' 20.3" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 14%.
The mask-weighted light curve shows the main emission occuring during a
pre-planned slew.  The burst location came into the BAT FoV at ~T-52 sec.
The first recorded peak started at ~T-51 sec and ending at ~T-50 sec.
The main, large peak started at ~T-50 sec, peaked at ~T-42 sec (~310 cnts/cm2/sec),
and ended at ~T-10 sec.  The spacecraft settled at T+0, and then BAT triggered
(a 64-sec image trigger) at the beginning a long slow peak starting at ~T+0 sec,
peaking at ~T+90 sec, and returning to baseline ~T+2000 sec.
T90 (15-350 keV) is 162.83 +- 1.36 sec (estimated error including systematics).
We note that (a) there is a possibility that there was emission from this burst
before it came into the BAT FoV at ~T-52 sec, and (b) that Fermi-GBM triggered
on this burst at 07:47:06.42 (T_bat-51 sec) [GCN/FERMI_GBM_FLIGHT_POSITION Notice,
The time-averaged spectrum from T-51.05 to T+223.50 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.21 +- 0.02.  The fluence in the 15-150 keV band is 3.1 +- 0.03 x 10^-4 erg/cm2.
The 1-sec peak photon flux measured from T-44.25 sec in the 15-150 keV band
is 331.0 +- 4.6 ph/cm2/sec.  All the quoted errors are at the 90% confidence
The results of the batgrbproduct analysis are available at
Looking for U.S. government information and services? Visit