TITLE:   GCN CIRCULAR
NUMBER:  20566
SUBJECT: GRB 170127B: Swift-BAT refined analysis
DATE:    17/01/29 16:03:01 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC),
J. K. Cannizzo (NASA/UMBC), J. R. Cummings (CPI),
N. Gehrels (GSFC), H. A. Krimm (NSF/USRA),
A. Y. Lien (GSFC/UMBC), C. B. Markwardt (GSFC),
J. P. Norris (BSU), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),

(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 170127B (trigger #735331)
(Cannizzo et al., GCN Circ. 20540).  The BAT ground-calculated position is
RA, Dec = 19.997, -30.340 deg which is
   RA(J2000)  =  01h 19m 59.2s
   Dec(J2000) = -30d 20' 25.2"
with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 75%.

The mask-weighted light curve shows a single-peaked structure that starts
and peaks at ~T0, and ends at ~T+0.6 s. T90 (15-350 keV) is 0.51 +- 0.14 sec
(estimated error including systematics).

The time-averaged spectrum from T+0.05 to T+0.64 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
0.89 +- 0.25.  The fluence in the 15-150 keV band is 1.0 +- 0.2 x 10^-7 erg/cm2.
The 1-sec peak photon flux measured from T-0.16 sec in the 15-150 keV band
is 1.1 +- 0.2 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

Using a 8-ms binned light curve, the lag analysis finds a lag of -4 (-17, +8) ms
for the 100-350 keV to 25-50 keV, and -12 (-8, +8) ms for the 50-100 keV to
15-25 keV band. These values are consistent with those of a short GRB. Moreover,
no extended emission are found.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/735331/BA/