[vsnet-grb-info 8108] GRB 090709B, Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9641
SUBJECT: GRB 090709B, Swift-BAT refined analysis
DATE:    09/07/09 23:02:32 GMT
FROM:    Hans Krimm at NASA-GSFC  <hans.a.krimm at nasa.gov>

T. N. Ukwatta (GWU), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC),
H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC/UMD), F. E. Marshall 
(NASA/GSFC),
D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC),
G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), J. Tueller (GSFC),
(i.e. the Swift-BAT team):

Using the data set from T-61 to T+242 sec from the recent telemetry 
downlink,
we report further analysis of BAT GRB 090709B (trigger #356912)
(Marshall et al., GCN Circ. 9633).  The BAT ground-calculated position is
RA, Dec = 93.522, 64.081 deg which is
   RA(J2000)  =  06h 14m 05.4s
   Dec(J2000) = +64d 04' 51.9"
with an uncertainty of 1.8 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 15%.

The mask-weighted light curve shows a main peak beginning at T-5 seconds 
and
continuing until T+10 sec.  There are then two much weaker peaks at 
approximately
T+25 and T+35 sec. At T+240 sec, a pre-planned spacecraft slew took the 
source
out of the BAT FOV. T90 (15-350 keV) is 27.2 +- 6.6 sec (estimated error 
including systematics).

The time-averaged spectrum from T-5.4 to T+35.9 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.51 +- 0.18.  The fluence in the 15-150 keV band is 1.5 +- 0.2 x 10-6 
erg/cm2.
The 1-sec peak photon flux measured from T+1.47 sec in the 15-150 keV band
is 2.1 +- 0.4 ph/cm2/sec.  All the quoted errors are at the 90% confidence
level.

The results of the batgrbproduct analysis are available at
http://gcn.gsfc.nasa.gov/notices_s/356912/BA/