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GCN Circular 23653

Subject
GRB 190109A: Swift-BAT refined analysis
Date
2019-01-09T15:23:32Z (5 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@milkyway.gsfc.nasa.gov>
T. Sakamoto (AGU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
J. D. Gropp (PSU), H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL), M. Stamatikos (OSU),
T. N. Ukwatta (LANL)  (i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 190109A (trigger #882747)
(Gropp, et al., GCN Circ. 23642).  The BAT ground-calculated position is
RA, Dec = 33.213, 38.111 deg, which is 
   RA(J2000)  =  02h 12m 51.2s 
   Dec(J2000) = +38d 06' 39.5" 
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 28%.
 
The mask-weighted light curve shows several overlapping peaks starting at ~T+1 sec,
peaking at ~T+40 sec, and returning to baseline at ~T+200 sec.
T90 (15-350 keV) is 115.0 +- 33.5 sec (estimated error including systematics).
 
The time-averaged spectrum from T+5.86 to T+205.36 sec (with a 1.03 sec gap
in the data at T+111.97 sec) is best fit by a power law with an exponential cutoff.
This fit gives a photon index 0.36 +- 0.47, and Epeak of 49.7 +- 4.0 keV
(chi squared 46.05 for 56 d.o.f.).  For this model the total fluence
in the 15-150 keV band is 5.5 +- 0.3 x 10^-6 erg/cm2 and the 1-sec peak flux
measured from T+38.82 sec in the 15-150 keV band is 1.9 +- 0.3 ph/cm2/sec.
A fit to a simple power law gives a photon index of 1.86 +- 0.08
(chi squared 87.76 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/882747/BA/
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