[vsnet-grb-info 6809] GRB 081024, Swift-BAT refined analysis

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8404
SUBJECT: GRB 081024, Swift-BAT refined analysis 
DATE:    08/10/24 14:51:55 GMT
FROM:    Jay R. Cummings at NASA/GSFC/Swift  <jayc at milkyway.gsfc.nasa.gov>

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), K. McLean (GSFC/UMD),
D. M. Palmer (LANL), A. M. Parsons (GSFC), T. Sakamoto (GSFC/UMBC),
G. Sato (ISAS), M. Stamatikos (GSFC/ORAU), G. Stratta (ASDC),
J. Tueller (GSFC), T. N. 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 081024 (trigger #332516)
(Stratta, et al., GCN Circ. 8398).  The BAT ground-calculated position is
RA, Dec = 27.891, 61.352 deg which is
  RA(J2000)  =  01h 51m 33.8s
  Dec(J2000) = +61d 21' 08.2"
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment).
This position is 1.3 arcmin from the enhanced XRT position (Beardmore et
al. GCN Circ. 8403).  The partial coding was 97%.

The mask-weighted lightcurve shows a slightly softer precursor peak about
0.05 sec long at T-1.7 sec, a peak about 0.3 seconds long at T-0.2 sec and
the largest peak 0.1 seconds long at T0.  T90 (15-350 keV) is 1.8 +- 0.6 
sec
(estimated error including systematics).

The time-averaged spectrum from T-1.7 to T+0.3 sec is best fit by a simple
power-law model.  The power law index of the time-averaged spectrum is
1.23 +- 0.21.  The fluence in the 15-150 keV band is
1.2 +- 0.2 x 10-07 erg/cm2.  The 1-sec peak photon flux measured from
T-0.73 sec in the 15-150 keV band is 1.1 +- 0.1 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/332516/BA/