Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The VLT-FLAMES Survey of Massive Stars: Stellar parameters and
  rotational velocities in NGC3293, NGC4755 and NGC6611   An analysis is presented of VLT-FLAMES spectroscopy for three Galactic
clusters, NGC3293, NGC4755 and NGC6611. Non-LTE model atmosphere calculations
have been used to estimate effective temperatures (from either the helium
spectrum or the silicon ionization equilibrium) and gravities (from the
hydrogen spectrum). Projected rotational velocities have been deduced from the
helium spectrum (for fast and moderate rotators) or the metal line spectrum
(for slow rotators). The observed Hertzsprung-Russell diagrams are compared
with theoretical predictions and some discrepancies including differences in
the main sequence luminosities are discussed. Cluster ages have been deduced
and evidence for non-coeval star formation is found for all three of the
clusters. Projected rotational velocities for targets in the older clusters,
NGC3293 and NGC4755, have been found to be systematically larger than those for
the field, confirming recent results in other similar age clusters. The
distribution of projected rotational velocities are consistent with a Gaussian
distribution of intrinsic rotational velocities. For the relatively unevolved
targets in the older clusters, NGC3293 and NGC4755, the peak of the velocity
distribution would be 250km/s with a full-width-half-maximum of approximately
180km/s. For NGC6611, the sample size is relatively small but implies a lower
mean rotational velocity. This may be evidence for the spin-down effect due to
angular momentum loss through stellar winds, although our results are
consistent with those found for very young high mass stars. For all three
clusters we deduce present day mass functions with Gamma-values in the range of
-1.5 to -1.8, which are similar to other young stellar clusters in the Milky
Way (Abridged).

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The categories of this paper are: dg-ga
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The categories of this paper are: chem-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: acc-phys
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-ex
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The categories of this paper are: solv-int
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The categories of this paper are: math
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The categories of this paper are: physics
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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: ao-sci
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The categories of this paper are: stat
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The categories of this paper are: hep-th
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The categories of this paper are: alg-geom
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The categories of this paper are: bayes-an