Issue |
A&A
Volume 449, Number 1, April I 2006
|
|
---|---|---|
Page(s) | 203 - 209 | |
Section | Interstellar and circumstellar matter | |
DOI | https://doi.org/10.1051/0004-6361:20054162 | |
Published online | 16 March 2006 |
Dust-scattered X-ray halos around gamma-ray bursts: GRB 031203 revisited and the new case of GRB 050713A
1
INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica Milano, via Bassini 15, 20133 Milano, Italy e-mail: tiengo@mi.iasf.cnr.it
2
Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano, Italy
Received:
6
September
2005
Accepted:
7
November
2005
Scattering by interstellar dust grains can produce time
variable X-ray halos around gamma-ray bursts (GRB). In particular,
an X-ray expanding ring is expected when a short pulse of X-ray
radiation is scattered by a narrow layer of dust in our Galaxy. We
present a new method for detecting and analyzing dust-scattering
expanding rings around gamma-ray bursts, using as an example the
XMM-Newton data of GRB 031203. Consistent with previous
reports, we found that the two expanding rings observed in this
burst are due to dust unevenly distributed in two layers at
distances of 870 and 1384 pc, with the more distant one responsible
for 70% of the total optical depth. Our modelling of the rings
indicates that the prompt X-ray emission of GRB 031203 was
consistent with a power law spectrum with photon index
and 1–2 keV fluence of
(
erg cm-2. Thanks to the
sensitivity of our technique, we discovered an expanding ring around
another burst recently observed with XMM-Newton, GRB 050713A.
In this case the dust layer is located at a distance of 364 pc, and
we derived a GRB fluence of (
erg cm-2 (1–2 keV). A search for similar halos in twelve other
bursts observed with XMM-Newton gave negative results.
Key words: gamma rays: bursts / methods: data analysis
© ESO, 2006
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