PRE-SPECTROSCOPIC FALSE-POSITIVE ELIMINATION OF KEPLER PLANET CANDIDATES

By N. Batalha, J. Rowe, R. Gilliland, Jon J. Jenkins, Douglas A. Caldwell, William J. Borucki, D. Koch, Jack J. Lissauer, E. Dunham, T. Gautier and 4 more. 2010

100 citations recorded by the source corpus.

Ten days of commissioning data (Quarter 0) and 33 days of science data (Quarter 1) yield instrumental flux time series of ∼150,000 stars that were combed for transit events, termed threshold crossing events(TCE), each having a total detection statistic above 7.1σ. TCE light curves are modeled as star+planet systems. Those returning a companion radius smaller than 2RJ are assigned a Kepler Object of Interest (KOI) number. The raw flux, pixel flux, and flux-weighted centroids of every KOI are scrutinized to assess the likelihood of being an astrophysical false positive versus the likelihood of being a planetary companion. This vetting using Kepler data is referred to as data validation (DV). Herein, we describe the DV metrics and graphics used to identify viable planet candidates amongst the KOIs. Light curve modeling tests for (1) the difference in depth of the odd- versus even-numbered transits, (2) evidence of ellipsoidal variations, and (3) evidence of a secondary eclipse event at phase = 0.5. Flux-weighted centroids are used to test for signals correlated with transit events with a magnitude and direction indicative of a background eclipsing binary. Centroid time series are complimented by analysis of images taken in-transit versus out-of-transit, the difference often revealing the pixel contributing the most to the flux change during transit. Examples are shown to illustrate each test. Candidates passing DV are submitted to ground-based observers for further false-positive elimination or confirmation/characterization.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

A SYSTEMATIC SEARCH FOR TRANSITING PLANETS IN THE K2 DATA (2015, methodology): “Centroid variations are feasible in K2 but must be treated differently than in the original Kepler mission where this effect was generally measured using difference imaging (Batalha et al. 2010; Bryson et al. 2013).”
KEPLER'S FIRST ROCKY PLANET: KEPLER-10b (2011, methodology): “Data validation for Kepler’s first planet discoveries (Kepler-4b, 5b, 6b, 7b, and 8b) is described in Batalha et al. (2010b).”
SOPHIE velocimetry of Kepler transit candidates XVII. The physical properties of giant exoplanets within 400 days of period (2015, background): “These false positives are mostly background eclipsing binaries (EBs) and background transiting planets that produce an in-transit astrometric signal, called centroid effect (Batalha et al. 2010; Bryson et al. 2013).”
KEPLER MISSION DESIGN, REALIZED PHOTOMETRIC PERFORMANCE, AND EARLY SCIENCE (2010, methodology): “…fit and remove local background for each star (Jenkins et al. 2010a), (6) measure any centroid shift during a transit at the sub-millipixel level (Batalha et al. 2010a), (7) perform astrometry and obtain parallaxes and hence distances to the stars (Monet et al. 2010), and (8) reprocess the data…”
The California-Kepler Survey. I. High-resolution Spectroscopy of 1305 Stars Hosting Kepler Transiting Planets (2017, background): “…that transformed CCD pixel values into planet candidates (Jenkins et al. 2010; Gilliland et al. 2010; Stumpe et al. 2012; Smith et al. 2012, 2016; Batalha et al. 2010a,b; Torres et al. 2011; Bryson et al. 2013; Christiansen et al. 2012, 2013, 2015, 2016; Thompson et al. 2015; McCauliff et al.…”
KEPLER ECLIPSING BINARY STARS. I. CATALOG AND PRINCIPAL CHARACTERIZATION OF 1879 ECLIPSING BINARIES IN THE FIRST DATA RELEASE (2010, methodology): “This scenario is a common source of false-positives for exoplanet transit detection as described in Batalha et al. (2010a) and applies to EB detection as well, though less frequently.”
KEPLER-18b, c, AND d: A SYSTEM OF THREE PLANETS CONFIRMED BY TRANSIT TIMING VARIATIONS, LIGHT CURVE VALIDATION, WARM-SPITZER PHOTOMETRY, AND RADIAL VELOCITY MEASUREMENTS (2011, methodology): “Batalha et al. (2010b) discuss the selection and characteristics of the Kepler target stars.”
LACK OF INFLATED RADII FOR KEPLER GIANT PLANET CANDIDATES RECEIVING MODEST STELLAR IRRADIATION (2011, methodology): “We removed the 14 KOI that have only one transit in Q0-Q2 and 9 other classified as “moderate” candidates, likely false positives, that exhibit centroid motion or difference of depth between 2 odd and even transits (Batalha et al. 2010).”
PLANETARY CANDIDATES OBSERVED BY KEPLER. III. ANALYSIS OF THE FIRST 16 MONTHS OF DATA (2012, background): “The depth of the phase-folded, evennumbered transits is compared to that of the odd-numbered transits as described in Batalha et al. (2010a) and Wu et al. (2010).”
ON THE LOW FALSE POSITIVE PROBABILITIES OF KEPLER PLANET CANDIDATES (2011, background): “…scenario can be avoided both by the comprehensive work that went into assembling the Kepler Input Catalog (Latham et al. 2005; Batalha et al. 2010b) and by the ability to photometrically identify giants by their elevated levels of stellar variability compared with dwarf stars…”
PHOTOMETRIC VARIABILITY IN KEPLER TARGET STARS. II. AN OVERVIEW OF AMPLITUDE, PERIODICITY, AND ROTATION IN FIRST QUARTER DATA (2010, methodology): “There are features in the log(g)-Teff plane that are due to artifacts in the way the KIC was constructed and in target selection criteria for the exoplanet search (Batalha et al. 2010).”
Kepler-22b: A 2.4 EARTH-RADIUS PLANET IN THE HABITABLE ZONE OF A SUN-LIKE STAR (2011, background): “The statistical properties of stars targeted by Kepler are described by Batalha et al. (2010a).”
POSSIBLE DISINTEGRATING SHORT-PERIOD SUPER-MERCURY ORBITING KIC 12557548 (2012, methodology): “(i) We checked difference images for each of Q1–Q6 and the apparent source of the photometric variations is coincident with the stellar image of KIC 12557548 (Batalha et al. 2010).”
ALMOST ALL OF KEPLER'S MULTIPLE-PLANET CANDIDATES ARE PLANETS (2012, methodology): “…ground-based transit searches, but the exquisite quality of Kepler photometry, combined with the ability to measure small deviations in center of light during transits (Jenkins et al. 2010; Batalha et al. 2010), have been used to cleanse the sample prior to presentation in Borucki et al. (2011).”
PLANETARY CANDIDATES FROM THE FIRST YEAR OF THE K2 MISSION (2015, methodology): “We followed Batalha et al. (2010) and identified as- trophysical false positives by searching for motion of flux centroids, high amplitude beaming or ellipsoidal variations in the light curve, and detections of secondary eclipses.”
A STUDY OF THE SHORTEST-PERIOD PLANETS FOUND WITH KEPLER (2014, methodology): “We obtained a secondary eclipse of 7.5± 1.4 ppm for Kepler-10b, a bit smaller than the value found by Fogtmann-Schulz et al. (2014) of 9.9±1.0 ppm, using only the SC data, but slightly larger than the original value reported by Batalha et al. (2010) of 5.8±2.5.”