Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Anomalous Double-Mode RR Lyrae Stars in the Magellanic Clouds   We report the discovery of a new subclass of double-mode RR Lyrae stars in
the Large and Small Magellanic Clouds. The sample of 22 pulsating stars have
been extracted from the latest edition of the OGLE collection of RR Lyrae
variables in the Magellanic System. The stars pulsating simultaneously in the
fundamental (F) and first-overtone (1O) modes have distinctly different
properties than regular double-mode RR Lyrae variables (RRd stars). The
$P_{1O}/P_F$ period ratios of our anomalous RRd stars are within a range
0.725-0.738, while "classical" double-mode RR Lyrae variables have period
ratios in the range 0.742-0.748. In contrast to the typical RRd stars, in the
majority of the anomalous pulsators the F-mode amplitudes are higher than the
1O-mode amplitudes. The light curves associated with the F-mode in the
anomalous RRd stars show different morphology than the light curves of, both,
regular RRd stars and single-mode RRab stars. Most of the anomalous double-mode
stars show long-term modulations of the amplitudes (Blazhko-like effect).
Translating the period ratios into the abundance parameter, Z, we find for our
stars Z in the range (0.002,0.005) - an order of magnitude higher values than
typical for RR Lyrae stars. The mass range of the RRd stars inferred from the
$W_I$ vs. $P_F$ diagram is (0.55-0.75) of the solar mass. These parameters
cannot be accounted for with single star evolution assuming a Reimers-like mass
loss. Much greater mass loss caused by interaction with other stars is
postulated. We blame the peculiar pulsation properties of our stars to the
parametric resonance instability of the 1O-mode to excitation of the F- and
2O-modes as with the inferred parameters of the stars $2\omega_{\rm
1O}\approx\omega_{\rm F}+\omega_{\rm 2O}$.

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The categories of this paper are: cond-mat
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The categories of this paper are: math-ph
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The categories of this paper are: hep-ex
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The categories of this paper are: supr-con
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The categories of this paper are: atom-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: funct-an
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The categories of this paper are: gr-qc
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The categories of this paper are: alg-geom
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The categories of this paper are: hep-th
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The categories of this paper are: cs
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The categories of this paper are: q-alg
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The categories of this paper are: hep-lat
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The categories of this paper are: physics
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The categories of this paper are: econ
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The categories of this paper are: chao-dyn