TITLE:   GCN CIRCULAR
NUMBER:  23659
SUBJECT: GRB 190109B: Swift-BAT refined analysis
DATE:    19/01/09 17:11:22 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott@milkyway.gsfc.nasa.gov>

M. Stamatikos (OSU), S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
D. M. Palmer (LANL), T. Sakamoto (AGU), B. Sbarufatti (PSU),
T. N. Ukwatta (LANL)   (i.e. the Swift-BAT team):
 
Using the data set from T-60 to T+243 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 190109B (trigger #882809)
(Sbarufatti, et al., GCN Circ. 23648).  The BAT ground-calculated position is
RA, Dec = 55.563, 63.592 deg, which is 
   RA(J2000)  =  03h 42m 15.1s 
   Dec(J2000) = +63d 35' 31.7" 
with an uncertainty of 1.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 60%.
 
The mask-weighted light curve shows a couple overlapping peaks starting at
~T-4sec, peaking at ~T+1 sec, and a shallow tail out to ~T+40 sec.
T90 (15-350 keV) is 5.92 +- 0.78 sec (estimated error including systematics).
 
The time-averaged spectrum from T-4.24 to T+3.31 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.58 +- 0.16.  The fluence in the 15-150 keV band is 4.8 +- 0.5 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.12 sec in the 15-150 keV band
is 1.7 +- 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/882809/BA/