THE RADIUS DISTRIBUTION OF PLANETS AROUND COOL STARS

By Timothy Morton, J. Swift. 2013

114 citations recorded by the source corpus.

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.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

STELLAR AND PLANETARY PROPERTIES OF K2 CAMPAIGN 1 CANDIDATES AND VALIDATION OF 17 PLANETS, INCLUDING A PLANET RECEIVING EARTH-LIKE INSOLATION (2015, methodology): “Like the original mission, we find significantly more small planets than large planets, as expected from the radius distributions measured from Kepler (Howard et al. 2012; Fressin et al. 2013; Morton & Swift 2014).”
A STELLAR-MASS-DEPENDENT DROP IN PLANET OCCURRENCE RATES (2014, methodology): “…limit (Seader et al. 2013), leading to a modified detection efficiency feff given by a linear ramp between an S/N of 6 and 12 (Fressin et al. 2013; Morton & Swift 2014): S/N 6 : feff = 0 6 < S/N 12 : feff = S/N − 6 6 (6) S/N > 12 : feff = 1 The number of stars N∗ in a given spectral type bin…”
The Habitability of Planets Orbiting M-dwarf Stars (2016, background): “…2015; Morton & Swift, 2014; Mulders et al., 2015c; Gaidos et al., 2016b), within which orbital period a typical M dwarfs hosts 2.0±0.45 planets per star (Morton & Swift, 2014) (consistent with the microlensing result of 1.9±0.5 planets per M dwarf between 1 and 104 M⊕ (Clanton & Gaudi, 2016)).”
How to Characterize Habitable Worlds and Signs of Life (2017, background): “…HZ limits (Kopparapu et al. 2013) 0.22 ± 0.08 1.0 ≤ r ≤ 2.0 Petigura et al. 2013 Host stars: solar type, HZ: 0.25–4.0 times flux on Earth (F⊕), twice as much flux as on Venus 0.25 0 < r < 1.4 Morton & Swift 2014 Host stars: cool dwarfs (T < 4,000 K) Construct planet radius distribution to…”
HOW TO CONSTRAIN YOUR M DWARF: MEASURING EFFECTIVE TEMPERATURE, BOLOMETRIC LUMINOSITY, MASS, AND RADIUS (2015, methodology): “Results based on observations by the NASA Kepler mission suggest that M dwarfs are teeming with rocky planets, with1 planet per low-mass star with orbital periods of less than 50 days (Cassan et al. 2012; Morton & Swift 2014; Gaidos et al. 2014).”
They are small worlds after all: revised properties of Kepler M dwarf stars and their planets (2015, methodology): “Our estimate within one standard deviation of previous estimates by DC13, Gaidos et al. (2014), Morton & Swift (2014), and DC15.”
CHARACTERIZING K2 PLANET DISCOVERIES: A SUPER-EARTH TRANSITING THE BRIGHT K DWARF HIP 116454 (2014, background): “In the Solar system, there are no planets with radii between 1–3 R⊕ while population studies with Kepler data have shown these planets to be nearly ubiquitous (Howard et al. 2012; Fressin et al. 2013; Petigura et al. 2013; Morton & Swift 2014).”
REVISED STELLAR PROPERTIES OF KEPLER TARGETS FOR THE QUARTER 1–16 TRANSIT DETECTION RUN (2013, background): “Recent planetoccurrence studies have used improved stellar properties either for specific parameter ranges such as cool dwarfs (Dressing & Charbonneau 2013; Morton & Swift 2013), or for a wide range of spectral types for dwarfs (Gaidos 2013).”
ZODIACAL EXOPLANETS IN TIME (ZEIT). III. A SHORT-PERIOD PLANET ORBITING A PRE-MAIN-SEQUENCE STAR IN THE UPPER SCORPIUS OB ASSOCIATION (2016, background): “Most planets around M dwarfs found by Kepler are 1-2.5R⊕ (Morton & Swift 2014; Mulders et al. 2015; Dressing & Charbonneau 2015; Gaidos et al. 2016b), while K2-33b is roughly twice this size at 5.04+0.34−0.37 R⊕.”
The California-Kepler Survey. VII. Precise Planet Radii Leveraging Gaia DR2 Reveal the Stellar Mass Dependence of the Planet Radius Gap (2018, methodology): “…magnitude-limited nature of CKS, our analysis was restricted to a fairly narrow range in M, spanning 0.85 to 1.2M. Previous studies of the radius distribution of planets orbiting M dwarfs have shown that these planets tend to be smaller on average (Morton & Swift 2014; Dressing & Charbonneau 2015).”
PLANETS AROUND LOW-MASS STARS (PALMS). IV. THE OUTER ARCHITECTURE OF M DWARF PLANETARY SYSTEMS (2014, background): “In particular, Swift et al. (2013) and Dressing & Charbonneau (2013) find that the average rate of small planets from Kepler is about one per star for periods shorter than 50 days, implying a vast galaxy-wide presence of rocky planets (Morton & Swift 2014).”
A Technique for Extracting Highly Precise Photometry for the Two-Wheeled Kepler Mission (2014, background): “…analyses of the frequency of exoplanets around solar mass stars (Howard et al. 2012; Youdin 2011; Fressin et al. 2013), around cool stars (Swift et al. 2013; Morton & Swift 2014), and in their stars’ habitable zones (Dressing & Charbonneau 2013; Petigura et al. 2013; Foreman-Mackey et al. 2014).”
FALSE POSITIVE PROBABILITIES FOR ALL KEPLER OBJECTS OF INTEREST: 1284 NEWLY VALIDATED PLANETS AND 428 LIKELY FALSE POSITIVES (2016, methodology): “This type of small-sample candidate culling using individually calculated FPPs has already been done in the literature (Morton & Swift 2014; Morton & Winn 2014); the publication of this full catalog allows the community to do the same.”
The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets (2017, methodology): “Since we do not perform any quantitative analysis on the wKDE we choose not to “de-bias” the wKDE as described in Morton & Swift (2014), but instead limit our quantitative analysis to the histograms that seem to be a more accurate representation of the underlying distributions in our simulations.”
Pale Orange Dots: The Impact of Organic Haze on the Habitability and Detectability of Earthlike Exoplanets (2016, background): “10 Blue Marble Space Institute of Science 1200 Westlake Ave N Suite 1006, Seattle, WA 98109 as 0.8 per star (Morton & Swift 2014).”
TERRESTRIAL PLANET OCCURRENCE RATES FOR THE KEPLER GK DWARF SAMPLE (2015, methodology): “Recent work has pointed out the nonnegligible bias in deriving planet occurrence rates without taking into account the full error distribution of Rp (Morton & Swift 2014; Foreman-Mackey et al. 2014; Silburt et al. 2015; Dressing & Charbonneau 2015).”
The Exoplanet Population Observation Simulator. I. The Inner Edges of Planetary Systems (2018, background): “Key findings are that planet occurrence rates increase with decreasing planet size (Howard et al. 2012) and remain roughly constant for planets smaller than 3 R⊕ (Petigura et al. 2013b; Morton & Swift 2014; Mulders et al. 2015b).”