GCN 43493: GRB 260120B: Swift-BAT refined analysis

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),
T. Sakamoto (AGU) (i.e. the Swift-BAT team):
 
Using the data set from T-769 to T+303 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 260120B (trigger #1442454)
(Ferro et al., GCN Circ. 43479).  The BAT ground-calculated position is
RA, Dec = 284.701, 61.905 deg which is 
   RA(J2000)  =  18h 58m 48.3s 
   Dec(J2000) = +61d 54' 19.2" 
with an uncertainty of 2.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 9%.
 
The BAT light curve showed a single-peaked structure with a duration of about 10 sec.
T90 (15-350 keV) is 4.48 +- 0.94 sec (estimated error including systematics).
 
The time-averaged spectrum from T-0.34 to T+4.59 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index -0.93 +- 1.35, 
and Epeak of 103.9 +- 38.6 keV (chi squared 48.41 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-06 erg/cm2
and the 1-sec peak flux measured from T+0.48 sec in the 15-150 keV band is
3.1 +- 0.8 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 0.95 +- 0.21 (chi squared 57.22 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/1442454