GCN Circular 38386

D. M. Palmer (LANL), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm
(NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
M. J. Moss (GSFC), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), C. Salvaggio
(INAF-OAB), T. Sakamoto (AGU) (i.e. the Swift-BAT team):

Using the data set from T-50 to T+242 sec from the recent telemetry
downlink, we report further analysis of BAT GRB 241127A (trigger #1270788)
(Salvaggio et al., GCN Circ. 38354
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 ).  The BAT ground-calculated position is
RA, Dec = 327.911, -56.652 deg which is
   RA(J2000)  =  21h 51m 38.5s
   Dec(J2000) = -56d 39' 08.1"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The
partial coding was 100%.

The mask-weighted light curve shows some weak emission that starts at ~T-21
s, followed by the main pulse that starts at ~T-1 s, peaks at ~T+1 s, and
ends at ~T+9 s. T90 (15-350 keV) is 26.02 +- 3.63 sec (estimated error
including systematics).

The time-averaged spectrum from T-20.83 to T+9.13 sec is best fit by a
power law with an exponential cutoff.  This fit gives a photon index 1.10
+- 1.01, and Epeak of 19.0 +- 12.56 keV (chi squared 52.96 for 56 d.o.f.).
For this model the total fluence in the 15-150 keV band is 6.5 +- 0.8 x
10^-07 erg/cm2 and the 1-sec peak flux measured from T+0.09 sec in the
15-150 keV band is 2.3 +- 0.2 ph/cm2/sec.  A fit to a simple power law
gives a photon index of 2.65 +- 0.21 (chi squared 60.15 for 57 d.o.f.).
All the quoted errors are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1270788