GCN Circular 5363
Subject
GRB 060728: Refined analysis of the Swift-BAT burst
Date
2006-07-29T16:09:28Z (18 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
D. Palmer (LANL), L. Barbier (GSFC), S. D. Barthelmy (GSFC),
J. Cummings (GSFC/ORAU), E. Fenimore (LANL), N. Gehrels (GSFC),
D. Hullinger (BYU-Idaho), H. Krimm (GSFC/USRA), M. Koss (GSFC/UMD),
C. Markwardt (GSFC/UMD), C. Pagani (PSU), A. Parsons (GSFC),
T. Sakamoto (GSFC/ORAU), G. Sato (GSFC/ISAS), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC)
on behalf of the Swift-BAT team:
Using the data set from T-239 to T+963 sec from recent telemetry downlinks,
we report further analysis of BAT GRB 060728 (trigger #221627)
(Pagani, et al., GCN Circ. 5360). The BAT ground-calculated position is
RA,Dec = 16.646,-41.390 deg {1h 6m 35.1s, -41d 23' 23.1"} (J2000)
+- 3.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 100%.
The mask-weighted lightcurve shows a smooth (at 10-sec binning) single peak
starting at T_zero and ending at ~T+70 sec. T90 (15-350 keV) is 60 +- 10 sec
(estimated error including systematics).
The time-averaged spectrum from T+0.0 to T+64.0 is best fit by a
simple power-law model. The power law index of the time-averaged spectrum
is 1.40 +- 0.45. The fluence in the 15-150 keV band is
2.4 +- 0.7 x 10^-07 erg/cm2. All the quoted errors are at the 90%
confidence level.
Given (a) the weakness of this event and (b) the lack of an x-ray counterpart
(Pagani et al., GCN Circ 5361) and optical counterpart (Pagani et al., 5360),
we can not rule out the possibility that this is a hard x-ray transient,
but is most likely a burst. We note that Swift has not had a long GRB
with no XRT detection when a prompt slew occurred.