Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: SDSS J163030.58+423305.8: A 40 minute Orbital Period Detached White
  Dwarf Binary   We report the discovery of a new detached, double white dwarf system with an
orbital period of 39.8 min. We targeted SDSS J163030.58+423305.8 (hereafter
J1630) as part of our radial velocity program to search for companions around
low-mass white dwarfs using the 6.5m MMT. We detect peak-to-peak radial
velocity variations of 576 km/s. The mass function and optical photometry rule
out main-sequence companions. In addition, no milli-second pulsar companions
are detected in radio observations. Thus the invisible companion is most likely
another white dwarf. Unlike the other 39 min binary SDSS J010657.39-100003.3,
follow-up high speed photometric observations of J1630 obtained at the McDonald
2.1m telescope do not show significant ellipsoidal variations, indicating a
higher primary mass and smaller radius. The absence of eclipses constrain the
inclination angle to <82deg. J1630 contains a pair of white dwarfs, 0.3 Msun
primary + >0.3 Msun invisible secondary, at a separation of >0.32 Rsun. The two
white dwarfs will merge in less than 31 Myr. Depending on the core composition
of the companion, the merger will form either a single core-He burning subdwarf
star or a rapidly rotating massive white dwarf. The gravitational wave strain
from J1630 is detectable by instruments like the Laser Interferometer Space
Antenna (LISA) within the first year of operation.

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The categories of this paper are: physics
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The categories of this paper are: chem-ph
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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: stat
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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: q-fin
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The categories of this paper are: plasm-ph
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The categories of this paper are: adap-org
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The categories of this paper are: comp-gas
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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: q-bio
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The categories of this paper are: cmp-lg
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The categories of this paper are: hep-ex