J/ApJ/806/183 Planet radii of Kepler Object of Interest (Wolfgang+, 2015)
How rocky are they? The composition distribution of Kepler's sub-Neptune planet
candidates within 0.15 AU.
Wolfgang A., Lopez E.
<Astrophys. J., 806, 183 (2015)>
=2015ApJ...806..183W 2015ApJ...806..183W (SIMBAD/NED BibCode)
ADC_Keywords: Planets ; Stars, diameters
Keywords: methods: statistical; planets and satellites: composition
Abstract:
The Kepler Mission has found thousands of planetary candidates with
radii between 1 and 4R⊕. These planets have no analogues in
our own solar system, providing an unprecedented opportunity to
understand the range and distribution of planetary compositions
allowed by planet formation and evolution. A precise mass measurement
is usually required to constrain the possible composition of an
individual super-Earth-sized planet, but these measurements are
difficult and expensive to make for the majority of Kepler planet
candidates (PCs). Fortunately, adopting a statistical approach helps
us to address this question without them. In particular, we apply
hierarchical Bayesian modeling to a subsample of Kepler PCs that is
complete for P<25 days and Rpl>1.2R⊕ and draw upon interior
structure models that yield radii largely independent of mass by
accounting for the thermal evolution of a gaseous envelope around a
rocky core. Assuming the envelope is dominated by hydrogen and helium,
we present the current-day composition distribution of the
sub-Neptune-sized planet population and find that H+He envelopes are
most likely to be ∼1% of these planets' total masses with an intrinsic
scatter of ±0.5 dex. We address the gaseous/rocky transition and
illustrate how our results do not result in a one-to-one relationship
between mass and radius for this sub-Neptune population; accordingly,
dynamical studies that wish to use Kepler data must adopt a
probabilistic approach to accurately represent the range of possible
masses at a given radius.
Description:
To select our sample, we begin with the cumulative Kepler KOI table
available at the NASA Exoplanet Archive, which at the time of access
(2013 December 2) consisted of the Q1-12 catalog (Rowe et al. 2015,
J/ApJS/217/16).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 57 215 Compositions of individual planets in sample
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/ApJS/217/16 : Kepler planetary candidates. V. 3yr Q1-Q12 (Rowe+, 2015)
J/ApJ/800/135 : HARPS-N radial velocities of KOI-69 (Dressing+, 2015)
J/ApJS/211/2 : Stellar properties of Q1-16 Kepler targets (Huber+, 2014)
J/ApJS/210/20 : Small Kepler planets radial velocities (Marcy+, 2014)
J/ApJS/210/19 : Kepler planetary candidates. IV. 22 months (Burke+, 2014)
J/ApJS/207/35 : Kepler pipeline signal-to-noise studies (Christiansen+, 2013)
J/ApJ/767/95 : Improved stellar param. of smallest KIC stars (Dressing+, 2013)
J/ApJS/204/24 : Kepler planetary candidates. III. (Batalha+, 2013)
J/PASP/124/1279 : Q3 Kepler's combined photometry (Christiansen+, 2012)
J/ApJS/197/8 : Kepler's candidate mult. transiting planets (Lissauer+, 2011)
J/ApJ/738/170 : False positive Kepler planet candidates (Morton+, 2011)
J/ApJ/736/19 : Kepler planetary candidates. II. (Borucki+, 2011)
J/other/Sci/330.653 : Detected planets in the Eta-Earth Survey (Howard+, 2010)
http://exoplanetarchive.ipac.caltech.edu/ : NASA Exoplanet Archive home page
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 --- KOI [49.01/4505.01] Kepler Object of Interest number
9- 16 I8 --- KIC Kepler target star identifier
18- 21 F4.2 Rgeo Rp [0.9/3.6] Planetary radius (1)
23- 26 F4.2 Rgeo e_Rp Lower bound on central 68% probability in Rp (2)
28- 31 F4.2 Rgeo E_Rp Upper bound on central 68% probability in Rp (2)
33- 37 F5.2 d Per [0.6/24.4] Period
39- 42 F4.2 Rsun R* [0.5/1.3] Stellar radius (1)
44- 47 F4.2 % fenv [0.06/6.4]? Fraction of planet mass existing
in gaseous H+He envelope
49 A1 --- R [R] R: indicates fenv posterior has mostly
rocky composition
51- 53 F3.1 % e_fenv Lower bound on central 68% probability in fenv (2)
55- 57 F3.1 % E_fenv Upper bound on central 68% probability in fenv (2)
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Note (1): The reported Rpl is the peak of the marginal posterior planet radius
distribution. Note that these are not exactly the same as the radii
reported at the NExSci Exoplanet Archive, as those values do not use
the full Hub14 stellar radius likelihood like we do here. Relatedly,
we report R* as the peak of the input stellar radius likelihood,
which is different than the choice used for the Archive.
Note (2): Together, the bounds give the coverage interval which encloses the
relevant posterior's central 68% probability region, in both cases
this is dominated by the stellar radius uncertainties. Note that the
two-dimensional C.I.s are actually ellipses that are covariant along
the direction of the Rpl, fenv locus shown in Figure 6; for reporting
simplicity, the marginal C.I.s are given here.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 19-Oct-2015