Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Light-travel-time diagnostics in early Supernova spectra: substantial
  mass loss of the IIb progenitor of SN 2013cu through a superwind   The progenitors of type-IIb supernovae (SNe) are believed to have lost their
H-rich envelopes almost completely in the direct pre-SN phase. Recently the
first 'flash spectrum' of a SN IIb (SN2013cu) has been presented, taken early
enough to study its immediate circumstellar medium (CSM). Similar to a previous
study by Groh (2014) we analyse the structure and chemical composition of the
optically-thick CSM using non-LTE model atmospheres. For the first time we take
light-travel time (LTT) effects on the spectrum formation into account, which
affect the shapes and strengths of the observable emission lines, as well as
the inferred SN luminosity. Based on the new CSM parameters we estimate a lower
limit of ~0.3Msun for the CSM mass, which is a factor 10-100 higher than
previous estimates. The spectral fit implies a CSM in the form of a homogeneous
and spherically symmetric superwind whose mass-loss rate exceeds common
expectations by up to two orders of magnitude. The derived chemical composition
is in agreement with a progenitor that has just left, or is just about to leave
the Red-Supergiant (RSG) stage, confirming the standard picture for the origin
of SNe IIb. Due to its extreme mass loss the SN progenitor will likely appear
as extreme RSG, Luminous Blue Variable (LBV), or Yellow Hypergiant (YHG). The
direct detection of a superwind, and the high inferred CSM mass suggest that
stellar wind mass loss may play an important role in the formation of SNe IIb.

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The categories of this paper are: quant-ph
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
24
The categories of this paper are: dg-ga
30
The categories of this paper are: q-alg
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The categories of this paper are: q-fin
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The categories of this paper are: acc-phys
3
The categories of this paper are: physics
10
The categories of this paper are: q-bio
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The categories of this paper are: stat
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The categories of this paper are: eess
33
The categories of this paper are: plasm-ph
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The categories of this paper are: solv-int
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The categories of this paper are: bayes-an
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The categories of this paper are: atom-ph
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The categories of this paper are: math-ph