TITLE:   GCN CIRCULAR
NUMBER:  26967
SUBJECT: GRB 200131A: Swift-BAT refined analysis
DATE:    20/02/03 00:35:33 GMT
FROM:    Amy Lien at GSFC  <amy.y.lien@nasa.gov>

T. Sakamoto (AGU), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), J. P. Norris (BSU),
D. M. Palmer (LANL), B. Sbarufatti (PSU),
 M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):

Using the data set from T-200 to T+963 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 200131A (trigger #953689)
(Sbarufatti et al., GCN Circ. 26953).  The BAT ground-calculated position is
RA, Dec = 3.067, 51.121 deg which is
   RA(J2000)  =  00h 12m 16.2s
   Dec(J2000) = +51d 07' 15.6"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 96%.

The mask-weighted light curve shows several bright overlapping
pulses that starts from ~T-3.5 s and ends at ~T+3. It is followed by
another weaker pulse at ~T+30 s and some weak emission that lasts
till ~T+60 s. The burst went out of the BAT FOV at T+472 s.
T90 (15-350 keV) is 32.74 +- 0.88 sec (estimated error including
systematics).

The time-averaged spectrum from T-3.45 to T+46.56 sec is best fit by a
simple
power-law model.  The power law index of the time-averaged spectrum is
1.32 +- 0.04.  The fluence in the 15-150 keV band is 7.0 +- 0.1 x 10^-6
erg/cm2.
The 1-sec peak photon flux measured from T+0.02 sec in the 15-150 keV band
is 26.9 +- 0.6 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The spectral lag of the initial bright structure from ~T-2.5 s to ~T+3 s
is 49 (+3, -3) ms for the 100-350 keV to 25-50 keV bands, and 43 (+5, -7) ms
for the 50-100 keV to 15-25 keV bands. These values are consistent with
this of long GRBs.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/953689/BA/