Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Precise distances from OGLE-IV member RR Lyrae stars in six bulge
  globular clusters   Context. RR Lyrae stars are useful standard candles allowing one to derive
accurate distances for old star clusters. Based on the recent catalogues from
OGLE-IV and Gaia Early Data Release 3 (EDR3), the distances can be improved for
a few bulge globular clusters. Aims. The aim of this work is to derive an
accurate distance for the following six moderately metal-poor, relatively
high-reddening bulge globular clusters: NGC 6266, NGC 6441, NGC 6626, NGC 6638,
NGC 6642, and NGC 6717. Methods. We combined newly available OGLE-IV catalogues
of variable stars containing mean I magnitudes, with Clement's previous
catalogues containing mean V magnitudes, and with precise proper motions from
Gaia EDR3. Astrometric membership probabilities were computed for each RR
Lyrae, in order to select those compatible with the cluster proper motions.
Applying luminosity-metallicity relations derived from BaSTI $\alpha$-enhanced
models (He-enhanced for NGC 6441 and canonical He for the other clusters), we
updated the distances with relatively low uncertainties. Results. Distances
were derived with the I and V bands, with a $5-8\%$ precision. We obtained 6.6
kpc, 13.1 kpc, 5.6 kpc, 9.6 kpc, 8.2 kpc, and 7.3 kpc for NGC 6266, NGC 6441,
NGC 6626, NGC 6638, NGC 6642, and NGC 6717, respectively. The results are in
excellent agreement with the literature for all sample clusters, considering
the uncertainties. Conclusions. The present method of distance derivation,
based on recent data of member RR Lyrae stars, updated BaSTI models, and robust
statistical methods, proved to be consistent. A larger sample of clusters will
be investigated in a future work.

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The categories of this paper are: patt-sol
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The categories of this paper are: gr-qc
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The categories of this paper are: supr-con
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The categories of this paper are: comp-gas
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The categories of this paper are: q-fin
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The categories of this paper are: cs
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The categories of this paper are: math
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The categories of this paper are: chao-dyn
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The categories of this paper are: nlin
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The categories of this paper are: dg-ga
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The categories of this paper are: physics
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The categories of this paper are: math-ph
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The categories of this paper are: quant-ph
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The categories of this paper are: ao-sci
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The categories of this paper are: hep-ph
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The categories of this paper are: chem-ph