Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Low-Resolution Spectroscopy of the Recurrent Nova T Pyxidis at its Early
  Stage of 2011 Outburst   We present our observational results of the recurrent nova T Pyxidis at its
early stage of 2011 outburst, using a low-resolution spectrograph
($R\approx400$) attached to a 28cm telescope. Total nights of our observation
are 11, among which 9 nights are during the pre-maximum stage. As a result we
have obtained a detailed evolutional feature of this recurrent nova on the way
to its maximum light. At first, on the earliest three nights ($-25 \sim -21$
days before maximum), broad and prominent emission lines such as Balmer series,
He I, He II, N II, N III and O I together with P Cygni profile are seen on the
spectra. The blueshifted absorption minima of H$\alpha$ yields a maximum
expansion velocity of approximately 2200 km s$^{-1}$, and the velocity
gradually decreases. Then, Helium and Nitrogen lines are weakened day by day.
After that (18 days before maximum light), Fe II (multiplets) lines emerge on
the spectra. These lines are then strengthened day by day, and the P Cygni
profiles also become more prominent. Accordingly, the expansion velocities
turns to be gradual increase. In addition, during the pre-maximum stage, nova
spectral type of T Pyx is thought to evolve from He/N type to Fe II one.

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The categories of this paper are: comp-gas
1
The categories of this paper are: cs
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat
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The categories of this paper are: chem-ph
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The categories of this paper are: q-alg
0
The categories of this paper are: hep-ph
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The categories of this paper are: bayes-an
23
The categories of this paper are: solv-int
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The categories of this paper are: cmp-lg
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The categories of this paper are: patt-sol
9
The categories of this paper are: nlin
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The categories of this paper are: funct-an
3
The categories of this paper are: physics
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The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th