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GCN Circular 35688

Subject
GRB 240204A: Swift-BAT refined analysis
Date
2024-02-06T02:39:23Z (4 months ago)
From
Sibasish Laha at GSFC <sibasish.laha@nasa.gov>
Via
email
T. Sakamoto (AGU),S. D. Barthelmy (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
A. Y. Lien (U Tampa), C. B. Markwardt (GSFC),
M. J. Moss (GSFC), D. M. Palmer (LANL),
T. Parsotan (GSFC), M. Stamatikos (OSU)
(i.e. the Swift-BAT team):

Swift-BAT triggered on GRB 240204A at 15:07:50.63 UT on 2024-02-04.
Swift slewed immediately, but didn’t have initial BAT information due to a telemetry gap.
Using the data set from T-239 to T+346 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 240204A (trigger #1212898)
(Cenko, et al., GCN Circ. 35666).  The BAT ground-calculated position is
RA, Dec = 104.290, 1.078 deg which is
   RA(J2000)  =  06h 57m 09.6s
   Dec(J2000) = +01d 04' 41.5"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 9%.

The BAT  light curve shows a complex structure with a duration of ~ 20 sec.
T90 (15-350 keV) is 18.93 +- 2.06 sec (estimated error including systematics).

The time-averaged spectrum from T-22.96 to T+8.96 sec is best fit by a power law
with an exponential cutoff.  This fit gives a photon index 1.21 +- 0.28,
and Epeak of 67.8 +- 12.6 keV (chi squared 41.34 for 56 d.o.f.).  For this
model the total fluence in the 15-150 keV band is 1.0 +- 0.0 x 10^-05 erg/cm2
and the 1-sec peak flux measured from T+0.08 sec in the 15-150 keV band is
22.1 +- 1.5 ph/cm2/sec.  A fit to a simple power law gives a photon index
of 1.80 +- 0.06 (chi squared 55.74 for 57 d.o.f.).  All the quoted errors
are at the 90% confidence level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/1212898/BA/

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