Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Photometric Survey to Search for Field sdO Pulsators   We present the results of a campaign to search for subdwarf O (sdO) star
pulsators among bright field stars. The motivation for this project is the
recent discovery by Randall et al. (2011), of four rapidly pulsating sdO stars
in the globular cluster Omega Cen, with Teff near 50,000 K, 5.4 < log g < 6.0,
and hydrogen-rich atmospheres. The only previously known sdO pulsator is
significantly hotter at 68,500 K and log g = 6.1. All of the sdO pulsators
identified so far are fainter than 17.4 in the V band and, thus, are poor
candidates for an in-depth follow-up with asteroseismology. We therefore
obtained high S/N light curves and spectroscopy for a number of field sdO stars
to attempt to discover bright counterparts to these stars, particularly the
Omega Cen pulsators. Our primary sample consisted of 19 sdO stars with
hydrogen-rich atmospheres, log N(He)/N(H) < -1.0, effective temperatures in the
range 40,000 K < Teff < 67,000 K, and surface gravities 5.3 < log g < 6.1. We
also observed 17 additional helium-rich sdO stars with log N(He)/N(H) > -0.1
and similar temperatures and gravities. To date, we have found no detectable
pulsations at amplitudes above 0.08% (4 times the mean noise level) in any of
the 36 field sdO stars that we observed. The presence of pulsations in Omega
Cen sdO stars and their apparent absence in seemingly comparable field sdO
stars is perplexing. While very suggestive, the significance of this result is
difficult to assess more completely right now due to remaining uncertainties
about the temperature width and purity of the Omega Cen instability strip and
the existence of any sdO pulsators with weaker amplitudes than the current
detection limit in globular clusters.

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The categories of this paper are: supr-con
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The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: adap-org
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The categories of this paper are: nlin
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The categories of this paper are: plasm-ph
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The categories of this paper are: eess
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The categories of this paper are: bayes-an
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The categories of this paper are: cmp-lg
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The categories of this paper are: gr-qc
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The categories of this paper are: acc-phys
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The categories of this paper are: hep-ex
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The categories of this paper are: atom-ph
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The categories of this paper are: econ
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The categories of this paper are: math
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The categories of this paper are: q-bio