[vsnet-grb-info 5268] GRB 071021, Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6966
SUBJECT: GRB 071021, Swift-BAT refined analysis
DATE:    07/10/21 19:33:04 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.gsfc.nasa.gov>

L. Barbier (GSFC), S. D. Barthelmy (GSFC), J. Cummings (GSFC/UMBC),
E. Fenimore (LANL), N. Gehrels (GSFC), H. Krimm (GSFC/USRA),
C. Markwardt (GSFC/UMD), D. Palmer (LANL), A. Parsons (GSFC),
T. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. Ukwatta (GWU)
(i.e. the Swift-BAT team):
 
Using the data set from T-239 to T+472 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 071021 (trigger #294974)
(Sakamoto, et al., GCN Circ. 6958).  The BAT ground-calculated position is
RA, Dec = 340.573, 23.764 deg, which is 
   RA(J2000)  = 22h 42m 17.6s 
   Dec(J2000) = 23d 45' 49" 
with an uncertainty of 3.4 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 78%.
 
The mask-weighted light curve shows a slow rise starting at ~T-30 sec and
peaking around T+85 sec.  The remaining portion of the lightcurve is
consistant with either a low-level constant emission out to ~T+225 sec or
with a decline to background around T+150 sec and then another weak peak
from ~T+180 to ~T+220 sec.  This latter interpretation is consistant with a
small flare in the XRT afterglow lightcurve around T+220 sec.
T90 (15-350 keV) is 225 +- 10 sec (estimated error including systematics).
 
The time-averaged spectrum from T-31.4 to T+252.2 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.70 +- 0.21.  The fluence in the 15-150 keV band is 1.3 +- 0.2 x 10^-6 erg/cm2.
The 1-sec peak photon flux measured from T+87.32 sec in the 15-150 keV band
is 0.7 +- 0.1 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level. 

This burst has several characteristics which are typical of high
redshift bursts.  Its duration is long (T90 = 225 sec) with relatively
few (two) significant peaks.  The 1-s peak flux is < 1.0 ph/cm2/s
and the power-law photon index (1.70) is < 2.