Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Spectral Temperature of Optically Thick Outflows with Application to
  Light Echo Spectra from $\eta$~Carinae's Giant Eruption   The detection by Rest et al. (2012) of light echoes from $\eta$ Carinae has
provided important new observational constraints on the nature of its 1840's
era giant eruption. Spectra of the echoes suggest a relatively cool spectral
temperature of about 5500K, lower than the lower limit of about 7000K suggested
in the optically thick wind outflow analysis of Davidson (1987). This has lead
to a debate about the viability of this steady wind model relative to
alternative, explosive scenarios. Here we present an updated analysis of the
wind outflow model using newer low-temperature opacity tabulations and
accounting for the stronger mass loss implied by the $>$10 Msun mass now
inferred for the Homunculus. A major conclusion is that, because of the sharp
drop in opacity due to free electron recombination for $T<$6500K, a low
temperature of about 5000K is compatible with, and indeed expected from, a wind
with the extreme mass loss inferred for the eruption. Within a spherical gray
model in radiative equilibrium, we derive spectral energy distributions for
various assumptions for the opacity variation of the wind, providing a basis
for comparisons with observed light echo spectra. The scaling results here are
also potentially relevant for other highly optically thick outflows, including
those from classical novae, giant eruptions of LBVs and SN Type IIn precursors.
A broader issue therefore remains whether the complex, variable features
observed from such eruptions are better understood in terms of a steady or
explosive paradigm, or perhaps a balance of these idealizations.

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The categories of this paper are: solv-int
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The categories of this paper are: dg-ga
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The categories of this paper are: alg-geom
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: mtrl-th
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The categories of this paper are: stat
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The categories of this paper are: hep-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: quant-ph
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The categories of this paper are: eess
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The categories of this paper are: cs
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The categories of this paper are: chao-dyn
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The categories of this paper are: math-ph
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The categories of this paper are: nucl-th
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The categories of this paper are: cmp-lg