Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: MIRACLES: atmospheric characterization of directly imaged planets and
  substellar companions at 4-5 $\mu$m. I. Photometric analysis of $\beta$ Pic
  b, HIP 65426 b, PZ Tel B and HD 206893 B   Directly imaged planets and substellar companions are key targets for the
characterization of self-luminous atmospheres. Their photometric appearance at
4-5 $\mu$m is sensitive to the chemical composition and cloud content of their
atmosphere. We aim at systematically characterizing the atmospheres of directly
imaged low-mass companions at 4-5 $\mu$m. We want to homogeneously process the
data and compile a photometric library at thermal wavelengths of these mostly
young, low-gravity objects. In this way, we want to find trends related to
their spectral type and surface gravity by comparing with isolated brown dwarfs
and predictions from atmospheric models. We have used the high-resolution,
high-contrast capabilities of NACO at the VLT to directly image the companions
of HIP 65426, PZ Tel, and HD 206893 in the NB4.05 and/or $M'$ filters. For the
same targets, and additionally $\beta$ Pic, we have also analyzed six archival
VLT/NACO datasets which were taken with the NB3.74, $L'$, NB4.05, and $M'$
filters. The $L'$-NB4.05 and $L'$-$M'$ colors of the studied sample are all red
while the NB4.05-$M'$ color is blue for $\beta$ Pic b, gray for PZ Tel B, and
red for HIP 65426 b and HD 206893 B (although typically with low significance).
The absolute NB4.05 and $M'$ fluxes of our sample are all larger than those of
field dwarfs with similar spectral types. Finally, the surface gravity of
$\beta$ Pic b has been constrained to $\log{g} = 4.17_{-0.13}^{+0.10}$ dex from
its photometry and dynamical mass. A red color at 3-4 $\mu$m and a blue color
at 4-5 $\mu$m might be (partially) caused by H$_2$O and CO absorption,
respectively. The red characteristics of $\beta$ Pic b, HIP 65426 b, and HD
206893 B at 3-5$\mu$m, as well as their higher fluxes in NB4.05 and $M'$
compared to field dwarfs, indicate that cloud densities are enhanced close to
the photosphere as a result of their low surface gravity.

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The categories of this paper are: comp-gas
3
The categories of this paper are: physics
36
The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: eess
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The categories of this paper are: supr-con
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The categories of this paper are: ao-sci
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The categories of this paper are: q-fin
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The categories of this paper are: q-alg
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The categories of this paper are: patt-sol
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The categories of this paper are: hep-th
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The categories of this paper are: mtrl-th
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The categories of this paper are: cs
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The categories of this paper are: hep-ex
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The categories of this paper are: adap-org
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The categories of this paper are: cond-mat