Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: On the formation of Lyman $\alpha$ emission from resonantly scattered
  continuum photons of GRB's afterglow   We study the formation and evolution of the spectral imprint of resonantly
scattered Lyman $\alpha$ photons in the context of GRB's continuum optical
afterglow. Based on an analytic model and a complete treatment of all the
scatterings using Monte Carlo simulations, we found that the flux of the
Ly$\alpha$ emission is mainly contributed by photons which are scattered only
once. The flux is of order $10^{-4}$ to $10^{-9}$ relative to the undecayed
maximum flux of the transmitted continuum, making the feature negligible but
potentially observable. If not obscured by host galaxy's DLA or intergalactic
neutral hydrogen, the feature may appear sometime from one hour to several
years when the directly transmitted light has faded away.This scattered
emission feature can be distinguished from Ly$\alpha$ photons of other origins
by its luminosity evolution, and by its gradual narrowing of profile with time.
The typical time scale for spectral variance is that of the light crossing time
of a hydrogen clump close to the GRB.

31
The categories of this paper are: ao-sci
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
9
The categories of this paper are: nlin
27
The categories of this paper are: comp-gas
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
20
The categories of this paper are: acc-phys
25
The categories of this paper are: patt-sol
19
The categories of this paper are: eess
12
The categories of this paper are: nucl-th
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ
37
The categories of this paper are: supr-con