GCN Circular 35523
Subject
GRB 240109A: Swift-BAT refined analysis
Date
2024-01-12T18:37:07Z (4 months ago)
From
Sibasish Laha at GSFC <sibasish.laha@nasa.gov>
Via
email
D. M. Palmer (LANL), 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), T. Parsotan (GSFC),
T. Sakamoto (AGU), M. Stamatikos (OSU)
(i.e. the Swift-BAT team):
Using the data set from T-61 to T+242 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 240109A (trigger #1207446)
(Dichiara et al., GCN Circ. 35501). The BAT ground-calculated position is
RA, Dec = 301.330, 16.566 deg which is
RA(J2000) = 20h 05m 19.1s
Dec(J2000) = +16d 33' 58.3"
with an uncertainty of 2.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 67%.
The BAT light curve shows a single peak with a duration ~0.5 sec.
T90 (15-350 keV) is 0.16 +- 0.06 sec (estimated error including systematics).
The time-averaged spectrum from T-0.04 to T+0.15 sec is better fit by a blackbody.
A simple power-law fit shows a photon index of 2.75 +-0.35 with a poor statistics (reduced chi2 of 1.9).
Instead, the black body fit shows the temperature of 12.2 +-1.3 keV
with a reasonable statistics (reduced chi2 of 1.2). So, the burst
prefers a soft spectrum. The fluence in the 15-150 keV band is 1.2 +- 0.4 x 10^-08 erg/cm2.
The 1-sec peak photon flux measured from T-0.44 sec in the 15-150 keV band
is 0.7 +- 0.2 ph/cm2/sec. 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/1207446/BA/