GCN Circular 10511
Subject
GRB 100316D: Swift-BAT refined analysis
Date
2010-03-16T23:16:32Z (15 years ago)
From
Scott Barthelmy at NASA/GSFC <scott@lheamail.gsfc.nasa.gov>
T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC),
J. R. Cummings (GSFC/UMBC), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA),
C. B. Markwardt (GSFC/UMD), D. M. Palmer (LANL), M. Stamatikos (GSFC/ORAU),
J. Tueller (GSFC), T. N. Ukwatta (GWU)
(i.e. the Swift-BAT team):
Using the data set from T-60 to T+243 sec from the telemetry downlinks,
we report further analysis of BAT GRB 100316D (trigger #416135)
(Stamatikos, et al., GCN Circ. 10496). The BAT ground-calculated position is
RA, Dec = 107.599, -56.275 deg, which is
RA(J2000) = 07h 10m 23.8s
Dec(J2000) = -56d 16' 28.9"
with an uncertainty of 3.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 85%.
The mask-weighted light curve is relatively flat. The emission started
before T-80 sec when the location came into the BAT FoV during a
Swift planned-target slew. Using the event-by-event data, the lightcurve
conitinue through the 64-sec integration of the image trigger and out to
at least T+240 sec. Using the on-board mask-weighted lightcurve,
the lightcurve continues out to at least T+740 sec where the data ends.
The time-averaged spectrum using just the T+0.0 to T+64.0 sec image-trigger
interval is best fit by a simple power-law model. The power law index of the
time-averaged spectrum is 2.29 +- 0.41. The fluence in the 15-150 keV band
is 3.0 +- 0.8 x 10^-7 erg/cm2. The 1-sec peak photon flux measured
from T+0.00 sec in the 15-150 keV band is 0.1 +- 0.0 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/416135/BA/
We note that this lightcurve is very non-typical for a GRB and that
the spectrum is soft. This is similar both in the temporal and spectral
properties to the GRB060218-SN2006aj burst (Camapana, et al.; Nature,
v224, p1008, Figure 1). In the 060218 burst, the BAT lightcurve was flat
from T-50 to T+300 sec. The X-ray temporal decay (Starling, GCN Circ 10505)
is shallow as it was in SN2006aj (Campana, Fig 1). We further note
that the 5 arcsec XRT error circle (GCN 10496) covers the edge
of an extended object (a pair of unresolved stars or a galaxy) in DSS.