Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Age of the Old Metal-Poor Globular Cluster NGC6397 Using WFC3/IR
  Photometry   Globular Clusters (GCs) in the Milky Way represent the ideal laboratory to
establish the age of the oldest stellar populations and to measure the
color-magnitude relation of stars. Infrared (IR) photometry of these objects
provides a new opportunity to accomplish this task. In particular, at low
stellar masses, the stellar main sequence (MS) in an IR color-magnitude diagram
(CMD) exhibits a sharp "kink" (due to opacity effects in M dwarfs), such that
lower mass and cooler dwarfs become bluer in the F110W - F160W color baseline
and not redder. This inversion of the color-magnitude relation offers the
possibility to fit GC properties using IR imaging, and to reduce their
uncertainties. Here, we used the IR channel of the Wide Field Camera 3 onboard
the Hubble Space Telescope to obtain new, deep high-resolution photometry of
the old metal-poor GC NGC6397. From the analysis of the GC CMD, we revealed
below the MS "kink" the presence of two MSs with different chemical
composition. We derived the cluster fiducial line and we compared it with a
grid of isochrones over a large range of parameter space, allowing age,
metallicity, distance and reddening to vary freely within reasonable selected
ranges. We derived an age of 12.6 Gyr with a random uncertainty sigma ~ 0.7
Gyr. These results confirm that the analysis of the IR color-magnitude of stars
provide a valuable tool to measure the GC ages and offers a new venue to
determine their absolute age to sub-Gyr accuracy with next generation IR
telescopes.

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The categories of this paper are: hep-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: hep-lat
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The categories of this paper are: mtrl-th
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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: funct-an
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The categories of this paper are: eess
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: math
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The categories of this paper are: cmp-lg
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The categories of this paper are: solv-int
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The categories of this paper are: q-bio
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The categories of this paper are: adap-org