Multiple Component Analysis of Time Resolved Spectra of GRB041006: A Clue to the Nature of Underlying Soft Component of GRBs

Kavli Affiliate: Gregory Prigozhin

| First 5 Authors: Yuji Shirasaki, Atsumasa Yoshida, Nobuyuki Kawai, Toru Tamagawa, Takanori Sakamoto

| Summary:

GRB 041006 was detected by HETE-2 at 12:18:08 UT on 06 October 2004. This GRB
displays a soft X-ray emission, a precursor before the onset of the main event,
and also a soft X-ray tail after the end of the main peak. The light curves in
four different energy bands display different features; At higher energy bands
several peaks are seen in the light curve, while at lower energy bands a single
broader bump dominates. It is expected that these different features are the
result of a mixture of several components each of which has different
energetics and variability. To reveal the nature of each component, we analysed
the time resolved spectra and they are successfully resolved into several
components. We also found that these components can be classified into two
distinct classes; One is a component which has an exponential decay of $E_{p}$
with a characteristic timescale shorter than $sim$ 30 sec, and its spectrum is
well represented by a broken power law function, which is frequently observed
in many prompt GRB emissions, so it should have an internal-shock origin.
Another is a component whose $E_{p}$ is almost unchanged with characteristic
timescale longer than $sim$ 60 sec, and shows a very soft emission and slower
variability. The spectrum of the soft component is characterized by either a
broken power law or a black body spectrum. This component might originate from
a relatively wider and lower velocity jet or a photosphere of the fireball. By
assuming that the soft component is a thermal emission, the radiation radius is
initially $4.4 times 10^{6}$ km, which is a typical radius of a blue
supergiant, and its expansion velocity is $2.4 times 10^{5}$ km/s in the
source frame.

| Search Query: ArXiv Query: search_query=au:”Gregory Prigozhin”&id_list=&start=0&max_results=10

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