Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: An Isolated White Dwarf with a 70 second Spin Period   We report the discovery of an isolated white dwarf with a spin period of 70
s. We obtained high speed photometry of three ultramassive white dwarfs within
100 pc, and discovered significant variability in one. SDSS J221141.80+113604.4
is a $1.27~M_{\odot}$ (assuming a CO core) magnetic white dwarf that shows
2.9\% brightness variations in the BG40 filter with a $70.32 \pm 0.04$ s
period, becoming the fastest spinning isolated white dwarf currently known. A
detailed model atmosphere analysis shows that it has a mixed hydrogen and
helium atmosphere with a dipole field strength of $B_d = 15$ MG. Given its
large mass, fast rotation, strong magnetic field, unusual atmospheric
composition, and relatively large tangential velocity for its cooling age,
J2211+1136 displays all of the signatures of a double white dwarf merger
remnant. Long term monitoring of the spin evolution of J2211+1136 and other
fast spinning isolated white dwarfs opens a new discovery space for substellar
and planetary mass companions around white dwarfs. In addition, the discovery
of such fast rotators outside of the ZZ Ceti instability strip suggests that
some should also exist within the strip. Hence, some of the mono-periodic
variables found within the instability strip may be fast spinning white dwarfs
impersonating ZZ Ceti pulsators.

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The categories of this paper are: q-alg
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The categories of this paper are: hep-th
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The categories of this paper are: atom-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: eess
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The categories of this paper are: quant-ph
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The categories of this paper are: nlin
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-ex
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The categories of this paper are: acc-phys
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The categories of this paper are: adap-org
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The categories of this paper are: physics
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The categories of this paper are: bayes-an
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The categories of this paper are: funct-an
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The categories of this paper are: math-ph
1
The categories of this paper are: cs