Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Homogeneity of Interstellar Krypton in the Galactic Disk   We present an analysis of high resolution HST Space Telescope Imaging
Spectrograph (STIS) observations of Kr I 1236 Angstrom absorption in seven
sight lines that probe a variety of interstellar environments. In combination
with krypton and hydrogen column densities derived from current and archival
STIS and Far-Ultraviolet Spectroscopic Explorer data, the number of sight lines
with reliable Kr/H ISM abundance ratios has been increased by 50% to
26--including paths that sample a range of nearly 5 orders of magnitude in
f(H_2), over 2 orders of magnitude in <n_H>, and extending up to 4.8 kpc in
length. For sight lines contained entirely within the local spiral arm (the
Orion Spur), the spread of Kr/H ratios about the mean of log_10[N(Kr)/N(H)]_ISM
= -9.02+/-0.02 is remarkably tight (0.06 dex), less than the typical datapoint
uncertainty. Intriguingly, the only two sight lines that extend through
neighboring structures, in particular gas associated with the
Carina/Sagittarius Arm, exhibit relatively large, near-solar krypton abundances
(log_10[N(Kr)/N(H)]_combined = -8.75+0.09_-0.11). Although these deviations are
only measured at the 2 sigma level, they suggest the possibility that krypton
abundances beyond the Orion Spur may differ from the local value.

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The categories of this paper are: mtrl-th
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The categories of this paper are: chem-ph
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The categories of this paper are: cs
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The categories of this paper are: funct-an
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The categories of this paper are: physics
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The categories of this paper are: ao-sci
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The categories of this paper are: gr-qc
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The categories of this paper are: stat
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The categories of this paper are: patt-sol
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The categories of this paper are: cmp-lg
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The categories of this paper are: alg-geom
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The categories of this paper are: nucl-th
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The categories of this paper are: nucl-ex
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: q-fin