[vsnet-grb-info 5615] GRB 080207, Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7277
SUBJECT: GRB 080207, Swift-BAT refined analysis
DATE:    08/02/09 00:55:04 GMT
FROM:    Jay R. Cummings at NASA/GSFC/Swift  <jayc at milkyway.gsfc.nasa.gov>

M. Stamatikos (GSFC/ORAU), 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),
J. L. Racusin (PSU), T. Sakamoto (GSFC/UMBC), G. Sato (GSFC/ISAS),
J. Tueller (GSFC), T. Ukwatta (GWU)
(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 080207 (trigger #302728)
(Racusin, et al., GCN Circ. 7264).  The BAT ground-calculated position
is RA, Dec = 207.514, 7.492 deg which is
   RA(J2000)  = 13h 50m 3.3s
   Dec(J2000) =  7d 29' 32"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 100%.

The mask-weighted light curve shows a long smooth rise starting at
~T-20 sec, peaking around T+100 sec, then dropping to a minimum around
T+200 sec, then rising again out to ~T+340 sec at which point the 
location went out of the BAT FOV when the spacecraft slewed to a new
target.  Based on the raw counting rates, which are somewhat sensitive
to photons through the side of the instrument, there was not significant
emission above about 50 keV after this time.  T90 (15-350 keV) is 
340 +- 20 sec (estimated error including systematics).

The time-averaged spectrum from T+4.7 to T+332.9 sec is best fit by a
power law with an exponential cutoff.  This fit gives a photon index
1.17 +- 0.27, and Epeak of 107.8 +- 72.5 keV (chi squared 51.31 for
56 d.o.f.).  For this model the total fluence in the 15-150 keV band is
6.1 +- 0.2 x 10^-06 erg/cm2 and the 1-sec peak flux measured from
T+330.34 sec in the 15-150 keV band is 1.0 +- 0.3 ph/cm2/sec.  A fit to
a simple power law gives a photon index of 1.58 +- 0.06 (chi squared
57.73 for 57 d.o.f.).  All the quoted errors are at the 90% confidence
level.

The BAT characteristics of this burst, particularly the long smooth
lightcurve, suggest that it might be at high redshift, but the high
absorption of the XRT spectrum (Racusin et al. GCN 7266) make it
unlikely.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/302728/BA/