Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spiral structure in IP Pegasi; how persistent is it?   We present spectroscopy of the dwarf nova IP Pegasi taken during two
consecutive nights, 5 and 6 days after the start of an outburst. Even this late
in the outburst, Doppler maps show marked spiral structure in the accretion
disc, at least as strongly as seen earlier in other outbursts of IP Peg. The
spiral shocks are present on both nights with no diminution in strength from
one night to the next. The light curves of the lines show an offset to earlier
phases, with the mid-eclipse of the emission lines displaced to phases between
-0.015 +- 0.001 and -0.045 +- 0.009. This cannot be explained by the presence
of the accretion shocks. As well as the fixed spiral pattern, the disc shows
strong flaring in the Balmer and HeII lines. Irradiation-induced emission is
seen from the companion star in the Balmer, HeI, HeII, MgII, CII, and other
lines. The emission is located near the poles of the companion star, suggesting
that the accretion disc shields the companion star substantially and thus has
an effective H/R of order 0.2 at EUV wavelengths. The Balmer emission is
distinctly broader than the other lines consistent with non-Doppler broadening.

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The categories of this paper are: cs
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The categories of this paper are: cond-mat
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The categories of this paper are: nucl-th
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The categories of this paper are: eess
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The categories of this paper are: econ
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The categories of this paper are: nucl-ex
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The categories of this paper are: solv-int
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The categories of this paper are: hep-th
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The categories of this paper are: q-fin
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The categories of this paper are: chem-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-ph
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The categories of this paper are: math-ph
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The categories of this paper are: mtrl-th
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The categories of this paper are: nlin
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The categories of this paper are: ao-sci