J/A+A/660/A102 Low-mass multi-planetary systems (Acuna+, 2022)
Water content trends in K2-138 and other low-mass multi-planetary systems.
Acuna L., Lopez T.A., Morel T., Deleuil M., Mousis O., Aguichine A.,
Marcq E., Santerne A.
<Astron. Astrophys., 660, A102 (2022)>
=2022A&A...660A.102A 2022A&A...660A.102A (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Exoplanets ; Optical
Keywords: stars: abundances - stars: individual: K2-138 -
planets and satellites: interiors -
planets and satellites: composition -
planets and satellites: individual: K2-138 - methods: numerical
Abstract:
Both rocky super-Earths and volatile-rich sub-Neptunes have
been found simultaneously in multi-planetary systems, suggesting that
these systems are appropriate to study different composition and
formation pathways within the same environment.
We perform a homogeneous interior structure analysis of five
multi-planetary systems to explore compositional trends and their
relation with planet formation. For one of these systems, K2-138, we
present revised masses and stellar host chemical abundances to improve
the constraints on the interior composition of its planets.
We conducted a line-by-line differential spectroscopic analysis on the
stellar spectra of K2-138 to obtain its chemical abundances and the
planetary parameters. We selected multi-planetary systems with five or
more low-mass planets (M<20M⊕) that have both mass and
radius data available. We carried out a homogeneous interior structure
analysis on the planetary systems K2-138, TOI-178, Kepler-11,
Kepler-102, and Kepler-80. We estimated the volatile mass fraction of
the planets in these systems assuming a volatile layer constituted of
water in steam and supercritical phases. Our interior-atmosphere model
took the effects of irradiation on the surface conditions into
account.
K2-138 inner planets present an increasing volatile mass fraction with
distance from their 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 multi-planetary 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.
Description:
We carried out a homogeneous interior modelling and composition
analysis of five multiplanetary systems that have five or more
low-mass planets (M<20M{earth}), rather than compiling the volatile
content estimates of previous works to eliminate the differences
between interior models as a possible bias when comparing the
compositional trends between planetary systems. In the case of the
TOI-178, Kepler-11, Kepler-102, and Kepler-80 systems, we used
previously published mass, radius, and stellar abundance data. In the
case of the K2-138 system, we completed the previous analysis with an
in-depth stellar spectroscopic analysis.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 60 21 Masses, radii, semi-major axis, and irradiation
temperature for the multi-planetary systems
TOI-178, Kepler-11, Kepler-102, and Kepler-80
table4.dat 72 27 Retrieved core mass fraction and water mass
fraction of planets in the multi-planetary
systems K2-138, TOI-178, Kepler-11, Kepler-102,
and Kepler-80, with our interior-atmosphere model
table5.dat 49 14 Atmospheric parameters retrieved for the planets
whose composition can accommodate a
water-dominated atmosphere (see text)
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- System System name
12 A1 --- Planet Planet designation within the system
14- 19 F6.3 Msun M Mass
21- 25 F5.3 Msun E_M Mass error (upper limit)
27- 31 F5.3 Msun e_M Mass error (lower limit)
33- 37 F5.3 Rsun R Radius
39- 43 F5.3 Rsun E_R Radius error (upper limit)
45- 49 F5.3 Rsun e_R Radius error (lower limit)
51- 55 F5.3 AU ad Semi-major axis
57- 60 I4 K Tirr Irradiation temperature
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- System System name
12 A1 --- Planet Planet designation within the system
14- 17 F4.2 --- CMF Core mass fraction
19- 22 F4.2 --- E_CMF Core mass fraction error (upper value)
24- 27 F4.2 --- e_CMF Core mass fraction error (lower value)
29 A1 --- l_WMF Limit flag on WMF
30- 35 F6.4 --- WMF Water mass fraction
36- 40 F5.3 --- E_WMF ? Water mass fraction error (upper value)
42- 46 F5.3 --- e_WMF ? Water mass fraction error (lower value)
48 A1 --- l_dobs-ret Limit flag on dobs-ret
49- 51 F3.1 --- dobs-ret Difference between the observational mean and
the retrieved mean in σ unit (1)
53 A1 --- l_DMH2 Limit flag on DMH2
54- 60 F7.3 Mgeo DMH2 Maximum estimate of atmospheric escape mass
loss due to H2
62 A1 --- l_DMH2O Limit flag on DMH2O
63- 66 F4.2 Mgeo DMH2O Maximum estimate of atmospheric escape mass
loss due to water Jeans escape
68 A1 --- l_DMXUV Limit flag on DMXUV
69- 72 F4.2 Mgeo DMXUV Maximum estimate of atmospheric escape mass
loss due to XUV photoevaporation
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Note (1): A low dobs-ret indicates that the assumption of a water-dominated
atmosphere is adequate for a particular planet (see text).
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- System System name
12 A1 --- Planet Planet designation within the system
14- 17 I4 K Tirr Equilibrium temperature assuming a null albedo
19- 22 I4 K T300 Atmospheric temperature at 300 bar
24- 26 I3 K e_T300 Atmospheric temperature at 300 bar error
28- 33 F6.1 km zatm Thickness of the atmosphere from the 300 bar
to 20 mbar
35- 37 I3 km e_zatm Thickness of the atmosphere from the 300 bar
to 20 mbar error
39- 43 F5.3 --- Ab Planetary Bond albedo
45- 49 F5.3 --- e_Ab Planetary Bond albedo error
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 24-Aug-2022