Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Voracious vortices in cataclysmic variables: II. Evidence for the
  expansion of accretion disc material beyond the Roche lobe of the accretor in
  HT Cassiopeia during its 2017 superoutburst   In our earlier Paper I we showed that the accretion disc radius of the dwarf
nova HT Cas in its quiescent state has not changed significantly during many
years of observations. It has remained consistently large, close to the tidal
truncation radius. This result is inconsistent with the modern understanding of
the evolution of the disc radius through an outburst cycle. Here we present a
new set of time-resolved spectra of HT Cas obtained in the middle of its 2017
superoutburst. We used Doppler tomography to map emission structures in the
system, which we compared with those detected in quiescence. We used solutions
of the restricted three-body problem to re-discuss the location of emission
structures and the disc size of HT Cas in quiescence. The superoutburst
spectrum is similar in appearance to the quiescent spectra, although the
strength of most of the emission lines decreased. However, the high-excitation
lines significantly strengthened in comparison with the Balmer lines. Many
lines show a mix of broad emission and narrow absorption components. H$\alpha$
in superoutburst was much narrower than in quiescence. Other emission lines
also narrowed in outburst, but they had not become as narrow as H$\alpha$.
Doppler maps of H$\alpha$ in quiescence, and of the H$\beta$ and HeI lines in
outburst are dominated by a bright emission arc in the right side of the
tomograms, which is located at and even beyond the theoretical truncation
limit. However, the bulk of the H$\alpha$ emission in outburst has
significantly lower velocities. We show that the accretion disc radius of HT
Cas during its superoutburst has become hot but remained the same size as it
was in quiescence. Instead, we detected cool gas beyond the Roche lobe of the
white dwarf that may have been expelled from the hot disc during the
superoutburst.

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The categories of this paper are: nucl-th
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The categories of this paper are: nlin
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The categories of this paper are: mtrl-th
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The categories of this paper are: hep-lat
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The categories of this paper are: quant-ph
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The categories of this paper are: funct-an
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The categories of this paper are: alg-geom
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The categories of this paper are: eess
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The categories of this paper are: q-alg
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The categories of this paper are: bayes-an
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The categories of this paper are: gr-qc
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The categories of this paper are: physics
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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: chem-ph
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The categories of this paper are: q-bio