Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: 2MASS J154043.42-510135.7: a new addition to the 5 pc population   The aim of the project is to find the stars nearest to the Sun and to
contribute to the completion of the stellar and substellar census of the solar
neighbourhood. We identified a new late-M dwarf within 5 pc, looking for high
proper motion sources in the 2MASS-WISE cross-match. We collected astrometric
and photometric data available from public large-scale surveys. We complemented
this information with low-resolution optical and near-infrared spectroscopy
with instrumentation on the ESO NTT to confirm the nature of our candidate. We
also present a high-quality medium-resolution VLT/X-shooter spectrum covering
the 400 to 2500 nm wavelength range. We classify this new neighbour as an
M7.0$\pm$0.5 dwarf using spectral templates from the Sloan Digital Sky Survey
and spectral indices. Lithium absorption at 670.8 nm is not detected in the
X-shooter spectrum, indicating that the M7 dwarf is older than 600 Myr and more
massive than 0.06 M$_{\odot}$. We also derive a trigonometric distance of 4.4
pc, in agreement with the spectroscopic distance estimate, making
2MASS\,J154043.42$-$510135.7 the nearest M7 dwarf to the Sun. This
trigonometric distance is somewhat closer than the $\sim$6 pc distance reported
by the ALLWISE team, who independently identified this object recently. This
discovery represents an increase of 25\% in the number of M7--M8 dwarfs already
known at distances closer than 8\,pc from our Sun. We derive a density of
$\rho$\,=\,1.9$\pm$0.9$\times$10$^{-3}$\,pc$^{-3}$ for M7 dwarfs in the 8 pc
volume, a value similar to those quoted in the literature. This new ultracool
dwarf is among the 50 nearest systems to the Sun, demonstrating that our
current knowledge of the stellar census within the 5 pc sample remains
incomplete. 2M1540 represents a unique opportunity to search for extrasolar
planets around ultracool dwarfs due to its proximity and brightness.

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The categories of this paper are: nucl-th
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The categories of this paper are: eess
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The categories of this paper are: stat
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The categories of this paper are: chao-dyn
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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: plasm-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: nlin
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The categories of this paper are: q-bio
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The categories of this paper are: gr-qc
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The categories of this paper are: bayes-an
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The categories of this paper are: math-ph
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The categories of this paper are: atom-ph
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The categories of this paper are: adap-org