[AAVSO-HEN] GRB 090123: Swift-BAT refined analysis

[grb at aavso.org]

The following is a GCN Circular circulated via the AAVSO network.
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TITLE:   GCN CIRCULAR
NUMBER:  8844
SUBJECT: GRB 090123: Swift-BAT refined analysis
DATE:    09/01/23 15:28:59 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

T. N. Ukwatta (GWU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
D. Grupe (PSU), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD),
D. M. Palmer (LANL), T. Sakamoto (GSFC/UMBC), G. Sato (ISAS),
M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC)
(i.e. the Swift-BAT team):
 
Using the data set from T-240 to T+962 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 090123 (trigger #340895)
(Grupe, et al., GCN Circ. 8842).  The BAT ground-calculated position is
RA, Dec = 6.794, -23.503 deg, which is 
   RA(J2000)  =  00h 27m 10.5s 
   Dec(J2000) = -23d 30' 12.6" 
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 36%.
 
The mask-weighted light curve shows multiple overlapping peaks starting
at ~T-48 sec, with the max peak at ~T+3 sec, and ending at ~T+120 sec.
T90 (15-350 keV) is 131 +- 23 sec (estimated error including systematics).
 
The time-averaged spectrum from T-49.6 to T+117.9 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.74 +- 0.12.  The fluence in the 15-150 keV band is 2.9 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+0.08 sec in the 15-150 keV band
is 1.7 +- 0.3 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/340895/BA/