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GCN Circular 2489

Subject
GRB 031203: Discovery of a dust echo
Date
2003-12-15T20:06:16Z (20 years ago)
From
Andrew Levan at U.of Leicester <anl@star.le.ac.uk>
S. Vaughan, R. Willingale, P.T. O'Brien, J. Osborne, A. Levan, J.
Tedds, T. Roberts, M. Watson (University of Leicester), D. Watson
(University of Copenhagen) report:

The first XMM-Newton observation of GRB031203 began at 2003-12-04, UT
04:09:29 and lasted for 58211 seconds (GCN2462). The GRB was
originally detected by the IBIS instrument on Integral at 2003-12-03,
UT 22:01:28 (GCN2459).

Analysis of the first XMM-Newton observation reveals a diffuse X-ray
halo centered around the GRB afterglow location. This halo is seen in
all three cameras of the EPIC instrument and is not due to scattered
optical or X-ray light within the instrument. The halo has the form of
a virtually complete ring which increases in radius through the
observation, indicative of the expected behaviour of a "light-echo" as
X-rays are scattered off dust at a distance of ~700 pc from the
observer.

GRB031203 is in the direction (Galactic) l = 255.74, b = -4.80
degrees, a line of sight which includes the Gum Nebula among other
nebulae and infrared sources. The derived distance to the scattering
medium is consistent with an origin in our Galaxy.

The X-ray spectrum of GRB031203 can be well represented by a powerlaw
with Photon index ~ 1.7. The scattered X-ray light has, as expected, a
softer spectrum with Photon index ~ 3.

Further analysis is underway.
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