[vsnet-grb-info 5610] GRB 080207, Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7272
SUBJECT: GRB 080207, Swift-BAT refined analysis
DATE:    08/02/08 15:19:29 GMT
FROM:    Scott Barthelmy at NASA/GSFC  <scott at lheamail.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+320 sec at which point the location went out
of the BAT FOV when the spacecraft slewed to a new target.
T90 (15-350 keV) is >300 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/