Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Anomalous X-Ray emission in GRB060904B: a Nickel line?   The detection of an extra component in GRB060904B X-ray spectra in addition
to the standard single power-law behaviour has recently been reported in the
literature. This component can be fit with different models; in particular the
addition of a spectral line provides the best representation.In this paper we
investigate the physical properties that the surrounding medium must have in
order to produce a spectral feature that can explain the detected emission. We
analyse and discuss how and if the detected spectral excess fits in different
theoretical models developed to explain the nature of line emission during the
afterglow phase of Gamma-Ray Bursts (GRBs). Trasmission and reflection models
have been considered. Given the high value (>>1) of the Thomson optical depth,
the emission is likely to arise in a reflection scenario. Within reflection
models, the external reflection geometry fails to predict the observed
luminosity. On the contrary, the detected feature can be explained in a funnel
scenario with typical opening angle theta of 5 degrees, Nickel mass of the
order of 0.1 M_o and T=10^6 K. For theta=20 degrees, assuming the reprocessing
material to be the SN shell, the detected emission implies a Nickel mass of 0.4
M_o at T=10^7 K and a metallicity 10 times the solar value. If the giant X-ray
flare that dominates the early XRT light curve is identified with the ionizing
source, the SN expansion began 3000 s before the GRB event.

18
The categories of this paper are: econ
1
The categories of this paper are: cs
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
29
The categories of this paper are: funct-an
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
12
The categories of this paper are: nucl-th
10
The categories of this paper are: q-bio
15
The categories of this paper are: nucl-ex
3
The categories of this paper are: physics
17
The categories of this paper are: q-fin
37
The categories of this paper are: supr-con
7
The categories of this paper are: hep-th