Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dynamical Mass of the Exoplanet Host Star HR 8799   HR 8799 is a young A5/F0 star hosting four directly imaged giant planets at
wide separations ($\sim$16-78 au) which are undergoing orbital motion and have
been continuously monitored with adaptive optics imaging since their discovery
over a decade ago. We present a dynamical mass of HR 8799 using 130 epochs of
relative astrometry of its planets, which include both published measurements
and new medium-band 3.1 $\mu$m observations that we acquired with NIRC2 at Keck
Observatory. For the purpose of measuring the host star mass, each orbiting
planet is treated as a massless particle and is fit with a Keplerian orbit
using Markov chain Monte Carlo. We then use a Bayesian framework to combine
each independent total mass measurement into a cumulative dynamical mass using
all four planets. The dynamical mass of HR 8799 is 1.47$^{+0.12}_{-0.17}$ \Msun
assuming a uniform stellar mass prior, or 1.46$^{+0.11}_{-0.15}$ \Msun with a
weakly informative prior based on spectroscopy. There is a strong covariance
between the planets' eccentricities and the total system mass; when the
constraint is limited to low eccentricity solutions of $e<0.1$, which is
motivated by dynamical stability, our mass measurement improves to
1.43$^{+0.06}_{-0.07}$ \Msun. Our dynamical mass and other fundamental measured
parameters of HR 8799 together with MESA Isochrones & Stellar Tracks grids
yields a bulk metallicity most consistent with [Fe/H]$\sim$ -0.25-0.00 dex and
an age of 10-23 Myr for the system. This implies hot start masses of 2.7-4.9
\Mjup for HR 8799 b and 4.1-7.0 \Mjup for HR 8799 c, d, and e, assuming they
formed at the same time as the host star.

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The categories of this paper are: eess
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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: hep-ex
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The categories of this paper are: math
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The categories of this paper are: hep-th
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The categories of this paper are: q-bio
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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: comp-gas
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The categories of this paper are: nucl-ex
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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: gr-qc
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The categories of this paper are: hep-lat
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The categories of this paper are: alg-geom