Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Atmospheric dynamics and the variable transit of KELT-9 b   We present a spectrally and temporally resolved detection of the optical Mg I
triplet at 7.8$\sigma$ in the extended atmosphere of the ultra-hot Jupiter
KELT-9 b, adding to the list of detected metal species in the hottest gas giant
currently known. Constraints are placed on the density and radial extent of the
excited hydrogen envelope using simultaneous observations of H$\alpha$ and
H$\beta$ under the assumption of a spherically symmetric atmosphere. We find
that planetary rotational broadening of $v_\text{rot} = 8.2^{+0.6}_{-0.7}$ km
s$^{-1}$ is necessary to reproduce the Balmer line transmission profile shapes,
where the model including rotation is strongly preferred over the non-rotating
model using a Bayesian information criterion comparison. The time-series of
both metal line and hydrogen absorption show remarkable structure, suggesting
that the atmosphere observed during this transit is dynamic rather than static.
We detect a relative emission feature near the end of the transit which
exhibits a P-Cygni-like shape, evidence of material moving at $\approx 50-100$
km s$^{-1}$ away from the planet. We hypothesize that the in-transit
variability and subsequent P-Cygni-like profiles are due to a flaring event
that caused the atmosphere to expand, resulting in unbound material being
accelerated to high speeds by stellar radiation pressure. Further spectroscopic
transit observations will help establish the frequency of such events.

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The categories of this paper are: quant-ph
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The categories of this paper are: adap-org
3
The categories of this paper are: physics
5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
36
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: bayes-an
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The categories of this paper are: math
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The categories of this paper are: hep-ex
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The categories of this paper are: q-bio
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The categories of this paper are: nlin
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The categories of this paper are: supr-con
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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: cs