THE FALSE POSITIVE RATE OF KEPLER AND THE OCCURRENCE OF PLANETS

By F. Fressin, G. Torres, D. Charbonneau, S. Bryson, J. Christiansen, C. Dressing, Jon M. Jenkins, Lucianne M. Walkowicz, N. Batalha. 2013

811 citations recorded by the source corpus.

The Kepler mission is uniquely suited to study the frequencies of extrasolar planets. This goal requires knowledge of the incidence of false positives such as eclipsing binaries in the background of the targets, or physically bound to them, which can mimic the photometric signal of a transiting planet. We perform numerical simulations of the Kepler targets and of physical companions or stars in the background to predict the occurrence of astrophysical false positives detectable by the mission. Using real noise level estimates, we compute the number and characteristics of detectable eclipsing pairs involving main-sequence stars and non-main-sequence stars or planets, and we quantify the fraction of those that would pass the Kepler candidate vetting procedure. By comparing their distribution with that of the Kepler Objects of Interest (KOIs) detected during the first six quarters of operation of the spacecraft, we infer the false positive rate of Kepler and study its dependence on spectral type, candidate planet size, and orbital period. We find that the global false positive rate of Kepler is 9.4%, peaking for giant planets (6–22 R⊕) at 17.7%, reaching a low of 6.7% for small Neptunes (2–4 R⊕), and increasing again for Earth-size planets (0.8–1.25 R⊕) to 12.3%. Most importantly, we also quantify and characterize the distribution and rate of occurrence of planets down to Earth size with no prior assumptions on their frequency, by subtracting from the population of actual Kepler candidates our simulated population of astrophysical false positives. We find that 16.5% ± 3.6% of main-sequence FGK stars have at least one planet between 0.8 and 1.25 R⊕ with orbital periods up to 85 days. This result is a significant step toward the determination of eta-earth, the occurrence of Earth-like planets in the habitable zone of their parent stars. There is no significant dependence of the rates of planet occurrence between 0.8 and 4 Earth radii with spectral type. In the process, we also derive a prescription for the signal recovery rate of Kepler that enables a good match to both the KOI size and orbital period distribution, as well as their signal-to-noise distribution.

Subfields: Astronomy and Astrophysics, Instrumentation

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In Astronomy and Astrophysics

1. Jon Fortney
2. D. Charbonneau
3. Timothy Morton
4. N. Madhusudhan
5. J. Johnson
6. J. Winn
7. M. Perryman
8. J. Owen

In Instrumentation

1. D. Charbonneau
2. Jon Fortney
3. Timothy Morton
4. J. Southworth
5. J. Winn
6. J. Johnson
7. N. Madhusudhan
8. E. Gaidos

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): “The fidelity of this sample is high: most of these candidates are truly planets (Morton & Johnson 2011; Fressin et al. 2013; Désert et al. 2015).”
• A SYSTEMATIC SEARCH FOR TRANSITING PLANETS IN THE K2 DATA (2015, background): “Noting that the average number of planets per star with periods less than 30 days is about 0.25 (Fressin et al. 2013), we can roughly estimate that we expect <10% of our candidates to be caused by nearby contaminating EBs.”
• THE KEPLER FOLLOW-UP OBSERVATION PROGRAM. I. A CATALOG OF COMPANIONS TO KEPLER STARS FROM HIGH-RESOLUTION IMAGING (2016, background): “…Mullally et al. 2015; Desert et al. 2015; McCauliff et al. 2015; Santerne et al. 2016; Morton et al. 2016), with current estimates for false positive rates ranging from ∼ 10% for small planets (Fressin et al. 2013) to as high as 55% for giant planets (Santerne et al. 2016; Morton et al. 2016).”
• REVISED STELLAR PROPERTIES OF KEPLER TARGETS FOR THE QUARTER 1–16 TRANSIT DETECTION RUN (2013, methodology): “…which have explored planet-occurrence rates using the Kepler sample (e.g., Catanzarite & Shao 2011; Howard et al. 2012; Traub 2012; Dong & Zhu 2013; Fressin et al. 2013; Petigura et al. 2013a,b), have mostly relied on stellar properties based on the Kepler Input Catalog (KIC, Brown et al. 2011,…”
• REVEALING A UNIVERSAL PLANET–METALLICITY CORRELATION FOR PLANETS OF DIFFERENT SIZES AROUND SOLAR-TYPE STARS (2013, background): “Although the planet occurrence rate has been extensively studied (Catanzarite & Shao 2011; Youdin 2011; Traub 2012; Howard et al. 2012; Fressin et al. 2013; Dressing & Charbonneau 2013), the dependence of the planet occurrence rate on metallicity is a relatively less-visited topic for the Kepler…”
• Close-in planetesimal formation by pile-up of drifting pebbles (2016, background): “In some of our models, the planetesimal annulus contains as much as 1000 Earth masses, which could allow for in situ formation of the close-in massive planets that have been detected around many stars (Fressin et al. 2013).”
• The Evaporation Valley in the Kepler Planets (2017, background): “It is similar to those obtained in earlier work (e.g. Fressin et al. 2013).”
• PLANETARY CANDIDATES OBSERVED BY KEPLER IV: PLANET SAMPLE FROM Q1–Q8 (22 MONTHS) (2013, background): “…population in the Galaxy can be determined from the observed planet candidate sample from Kepler using a thorough understanding of the selection effects and sources of contamination (e.g., Youdin 2011; Howard et al. 2012; Fressin et al. 2013; Christiansen et al. 2013; Dressing & Charbonneau 2013).”
• VALIDATION OF KEPLER'S MULTIPLE PLANET CANDIDATES. III. LIGHT CURVE ANALYSIS AND ANNOUNCEMENT OF HUNDREDS OF NEW MULTI-PLANET SYSTEMS (2014, background): “The remaining 2530 systems are composed of primarily exoplanetary systems with an expected FP rate of approximately 10% due to photometric blends (Morton & Johnson 2011; Fressin et al. 2013; Santerne et al. 2013).”
• DETECTION OF AN ATMOSPHERE AROUND THE SUPER-EARTH 55 CANCRI E (2015, background): “…velocity statistics, superEarths are the most abundant planets, especially around late-type stars (e.g. Mayor et al. 2011; Howard et al. 2012; Fressin et al. 2013; Dressing & Charbonneau 2013). angelos.tsiaras.14@ucl.ac.uk The Wide Field Camera 3 (WFC3) onboard the Hubble Space Telescope…”
• THE OCCURRENCE RATE OF SMALL PLANETS AROUND SMALL STARS (2013, background): “…but we count this system as a quadruple planet system because KOI 952.05 was not included in the February 2012 planet candidate list. ies have demonstrated that the false positive rate is low for the planet candidates identified by the Kepler team (Morton & Johnson 2011; Fressin et al. 2013).”
• IN SITU FORMATION AND DYNAMICAL EVOLUTION OF HOT JUPITER SYSTEMS (2015, background): “Instead, hot “SuperEarths,” planets with P < 100 days and m < 30M⊕ are extremely common, with 30-50% of main sequence stars in the solar neighborhood serving as hosts (Fressin et al. 2013; Dressing and Charbonneau 2013, 2015; Petigura et al. 2013; Mulders et al. 2015; Winn and Fabrycky 2015).”
• Predictions of the WFIRST Microlensing Survey. I. Bound Planet Detection Rates (2018, background): “WFIRST has a high-detection efficiency for large-mass planets, but these have consistently been shown to be rare (e.g., Cumming et al. 2008; Howard et al. 2010; Cassan et al. 2012; Fressin et al. 2013; Shvartzvald et al. 2016; Suzuki et al. 2016).”
• Trumpeting M dwarfs with CONCH-SHELL: a catalogue of nearby cool host-stars for habitable exoplanets and life (2014, methodology): “We required a simulated SNR > 12 for detection; at this threshold the rate of false positives among actual Kepler candidates is very low (Fressin et al. 2013) and we neglect any such adjustment.”
• A PLATEAU IN THE PLANET POPULATION BELOW TWICE THE SIZE OF EARTH (2013, background): “We recognize the independent and complementary work of Fressin et al. (2013), who arrive at similar estimates of planet occurrence.”
• ZODIACAL EXOPLANETS IN TIME (ZEIT). III. A SHORT-PERIOD PLANET ORBITING A PRE-MAIN-SEQUENCE STAR IN THE UPPER SCORPIUS OB ASSOCIATION (2016, methodology): “Many known exoplanets orbit within 0.1 AU of their host star, where they are more readily detected by the transit and Doppler methods (e.g., Howard et al. 2010; Fressin et al. 2013).”
• KEPLER PLANETS: A TALE OF EVAPORATION (2013, background): “…most careful studies to date have yet to have sufficient radius resolution to confirm this feature (Howard et al. 2012; Petigura et al. 2013; Fressin et al. 2013), it is hinted at by Morton & Swift (2013) who construct a probability distribution function rather than using histograms with…”
• PLANETARY CANDIDATES OBSERVED BY KEPLER. VI. PLANET SAMPLE FROM Q1–Q16 (47 MONTHS) (2015, background): “The true false positive rates of our catalogs are not known (e.g., Dressing et al. 2014; Lissauer et al. 2014; Rowe et al. 2014; Fressin et al. 2013; Morton et al. 2011), and this must be addressed when deriving occurrence rates.”
• The frequency of planetary debris around young white dwarfs (2014, background): “Analysis of transiting planet candidates fromKepler puts the frequency of earth-sized planets with orbital periods< 85 days at 16.5± 3.6% (Fressin et al. 2013), whereas microlensing, which is sensitive to planetson longer period orbits, suggests that the fraction of stars with cool Neptunes or…”