J/ApJ/791/10 Radius distribution of planets around cool stars (Morton+, 2014)
The radius distribution of planets around cool stars.
Morton T.D., Swift J.
<Astrophys. J., 791, 10 (2014)>
=2014ApJ...791...10M 2014ApJ...791...10M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, dwarfs ; Stars, double and multiple ; Planets ;
Stars, diameters
Keywords: methods: statistical - planets and satellites: fundamental parameters
Abstract:
We calculate an empirical, non-parametric estimate of the shape of the
period-marginalized radius distribution of planets with periods less
than 150 days using the small yet well-characterized sample of cool
(Teff< 4000 K) dwarf stars in the Kepler catalog. In particular, we
present and validate a new procedure, based on weighted kernel density
estimation, to reconstruct the shape of the planet radius function
down to radii smaller than the completeness limit of the survey at the
longest periods. Under the assumption that the period distribution of
planets does not change dramatically with planet radius, we show that
the occurrence of planets around these stars continues to increase to
below 1 R☉, and that there is no strong evidence for a
turnover in the planet radius function. In fact, we demonstrate using
many iterations of simulated data that a spurious turnover may be
inferred from data even when the true distribution continues to rise
toward smaller radii. Finally, the sharp rise in the radius
distribution below ∼3 R☉ implies that a large number of
planets await discovery around cool dwarfs as the sensitivities of
ground-based transit surveys increase.
Description:
First, we focus exclusively on the smallest stars in the Kepler target
sample as a well-characterized subsample, due to both the photometric
recalibration of stellar properties presented by Dressing &
Charbonneau (2013, J/ApJ/767/95) and because the host stars of many of
the Kepler objects of interest (KOIs) in this sample have been
investigated spectroscopically (Muirhead et al. 2014, J/ApJS/213/5;
Muirhead et al. 2012ApJ...747..144M 2012ApJ...747..144M). Second, we aim to reconstruct as
faithfully as possible the detailed shape of the radius function,
avoiding both the limitations of histogram binning and the assumption
that the distribution follows a power law-a non-parametric,
non-histogram approach to this problem has not yet been attempted.
Finally, in order to investigate any potential flattening or turnover
of the distribution, we extend planet occurrence analysis to radii
smaller than has been attempted before, introducing a new technique
that allows proper marginalization over period even for radii for
which the Kepler survey is beginning to be incomplete.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 48 130 Data Used in Radius wKDE
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/ApJ/767/95 : Improved stellar parameters of smallest KIC stars
(Dressing+, 2013)
J/ApJS/213/5 : Cool KOIs. VI. H- and K- band spectra (Muirhead+, 2014)
J/ApJ/800/85 : Teff, radii and luminosities of cool dwarfs (Newton+, 2015)
J/ApJS/218/26 : Parameters of planets orbiting coolest dwarfs (Swift+, 2015)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 7 A7 --- KOI Kelper Object of Interest identifier (NNNN.NN)
9 A1 --- f_KOI [ab] Flag on KOI (1)
11- 15 F5.2 Rgeo Rp Planetary radius; Earth radii
17- 21 F5.2 Rgeo E_Rp Upper 1σ error in Rp
23- 27 F5.2 Rgeo e_Rp Lower 1σ error in Rp
29- 32 F4.2 --- etaDis Discovery efficiency (2)
34- 40 E7.1 --- FPP Probability signal is a false positive
42 A1 --- f_FPP [c] Flag on FPP (3)
44- 48 F5.1 --- Weight Weight factor (4)
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Note (1): Flag as follows :
a = Planet radius based on spectroscopic stellar parameters from the
analysis of Muirhead et al. (2012ApJ...750L..37M 2012ApJ...750L..37M) or Muirhead et al.
(in prep).
b = Spectroscopic stellar characterization not available, so planet radius
based on stellar parameters from Dressing & Charbonneau
(2013, J/ApJ/767/95).
Note (2): The fraction of planets in this thought experiment with transiting
orbital geometries that could have been detected by the survey.
Note (3): Flag as follows :
c = FPPs for these KOIs are not calculated. For those that are
dispositioned "FALSE POSITIVE" on the NExScI archive, a value of 1 is
assigned; for those for which the Kepler pipeline-derived planet radii
are more than 30% discrepant from the Rp listed here, a FPP of 0.10
is assigned.
Note (4): Appropriately calculated individual weight factors that renormalize
the kernels to correct for missing planets, as discussed in
Section 2.1.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 23-Mar-2017