GCN Circular 43355

Subject

GRB 260104A: Swift-BAT refined analysis

Event

GRB 260104A

Date

2026-01-09T03:01:10Z (4 days ago)

From

Tyler Parsotan at NASA GSFC <tyler.parsotan@nasa.gov>

Via

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

Using the data set from T-240 to T+962 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 260104A (trigger #1430212)
(Caputo, et al., GCN Circ. 43315Loading...
 
 ).  The BAT ground-calculated position is
RA, Dec = 337.395, -21.291 deg which is
   RA(J2000)  =  22h 29m 34.8s
   Dec(J2000) = -21d 17' 27.5"
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 99%.

The mask-weighted light curve shows two pulses. T90 (15-350 keV) is 13.26 +- 2.65 sec (estimated error including systematics).

The time-averaged spectrum from T-10.09 to T+5.22 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 0.32 +- 1.08,
and Epeak of 42.5 +- 8.8 keV (chi squared 67.04 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 3.5 +- 0.5 x 10^-07 erg/cm2
and the 1-sec peak flux measured from T-0.23 sec in the 15-150 keV band is
1.3 +- 0.2 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.85 +- 0.16 (chi squared 76.81 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/1430212