Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Water content trends in K2-138 and other low-mass multiplanetary systems   Super-Earths and sub-Neptunes have been found simultaneously in
multiplanetary systems, suggesting that they are appropriate to study
composition and formation within the same environment. We perform a homogeneous
interior structure analysis of five multiplanetary systems to explore the
compositional trends and its relation with planet formation. For K2-138, we
present revised masses and stellar host chemical abundances to improve the
constraints on the planetary interior. We conduct a line-by-line differential
spectroscopic analysis on the stellar spectra to obtain its chemical abundances
and the planetary parameters. We select multiplanetary systems with five or
more low-mass planets that have both mass and radius data available. We carry
out a homogeneous interior structure analysis on the systems K2-138, TOI-178,
Kepler-11, Kepler-102 and Kepler-80 and estimate the volatile mass fraction of
their planets assuming a volatile layer constituted of water in steam and
supercritical phases. Our interior-atmosphere model takes into account the
effects of irradiation on the surface conditions. K2-138 inner planets present
an increasing volatile mass fraction with distance from its host star, while
the outer planets present an approximately constant water content. This is
similar to the trend observed in TRAPPIST-1 in a previous analysis with the
same interior-atmosphere model. The Kepler-102 system could potentially present
this trend. In all multiplanetary systems, the low volatile mass fraction of
the inner planets could be due to atmospheric escape while the higher volatile
mass fraction of the outer planets can be the result of accretion of ice-rich
material in the vicinity of the ice line with later inward migration.
Kepler-102 and Kepler-80 present inner planets with high core mass fractions
which could be due to mantle evaporation, impacts or formation in the vicinity
of rocklines.

27
The categories of this paper are: comp-gas
36
The categories of this paper are: cmp-lg
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ
31
The categories of this paper are: ao-sci
26
The categories of this paper are: bayes-an
21
The categories of this paper are: adap-org
25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
29
The categories of this paper are: funct-an
35
The categories of this paper are: mtrl-th
16
The categories of this paper are: stat
17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
30
The categories of this paper are: q-alg