Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Searches for Gravitational Waves from Known Pulsars at Two Harmonics in
  the Second and Third LIGO-Virgo Observing Runs   We present a targeted search for continuous gravitational waves (GWs) from
236 pulsars using data from the third observing run of LIGO and Virgo (O3)
combined with data from the second observing run (O2). Searches were for
emission from the $l=m=2$ mass quadrupole mode with a frequency at only twice
the pulsar rotation frequency (single harmonic) and the $l=2, m=1,2$ modes with
a frequency of both once and twice the rotation frequency (dual harmonic). No
evidence of GWs was found so we present 95\% credible upper limits on the
strain amplitudes $h_0$ for the single harmonic search along with limits on the
pulsars' mass quadrupole moments $Q_{22}$ and ellipticities $\varepsilon$. Of
the pulsars studied, 23 have strain amplitudes that are lower than the limits
calculated from their electromagnetically measured spin-down rates. These
pulsars include the millisecond pulsars J0437\textminus4715 and
J0711\textminus6830 which have spin-down ratios of 0.87 and 0.57 respectively.
For nine pulsars, their spin-down limits have been surpassed for the first
time. For the Crab and Vela pulsars our limits are factors of $\sim 100$ and
$\sim 20$ more constraining than their spin-down limits, respectively. For the
dual harmonic searches, new limits are placed on the strain amplitudes $C_{21}$
and $C_{22}$. For 23 pulsars we also present limits on the emission amplitude
assuming dipole radiation as predicted by Brans-Dicke theory.

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The categories of this paper are: math-ph
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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: solv-int
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The categories of this paper are: chem-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: patt-sol
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The categories of this paper are: acc-phys
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The categories of this paper are: cond-mat
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The categories of this paper are: ao-sci
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The categories of this paper are: q-fin
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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: mtrl-th
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The categories of this paper are: hep-th
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The categories of this paper are: dg-ga