SOPHIE velocimetry of Kepler transit candidates VII. A false-positive rate of 35% for Kepler close-in giant candidates

By A. Santerne, R. D'iaz, C. Moutou, F. Bouchy, G. Hébrard, J. Almenara, A. Bonomo, M. Deleuil, Nuno C. Santos. 2012

148 citations recorded by the source corpus.

The false-positive probability (FPP) of Kepler transiting candidates is a key value for statistical studies of candidate properties. A previous investigation of the stellar population in the Kepler field has provided an estimate for the FPP of less than 5% for most of the candidates. We report here the results of our radial velocity observations on a sample of 46 Kepler candidates with a transit depth greater than 0.4%, orbital period less than 25 days and host star brighter than Kepler magnitude 14.7. We used the SOPHIE spectrograph mounted on the 1.93-m telescope at the Observatoire de Haute-Provence to establish the nature of the transiting candidates. In this sample, we found five undiluted eclipsing binaries, two brown dwarfs, six diluted eclipsing binaries, and nine new transiting planets that complement the 11 already published planets. The remaining 13 candidates were not followed-up or remain unsolved due to photon noise limitation or lack of observations. From these results we computed the FPP for Kepler close-in giant candidates to be 34.8% +/- 6.5%. We aimed to investigate the variation of the FPP for giant candidates with the longer orbital periods and found that it should be constant for orbital periods between 10 and 200 days. This significantly disagrees with the previous estimates. We discuss the reasons for this discrepancy and the possible extension of this work toward smaller planet candidates. Finally, taking the false-positive rate into account, we refined the occurrence rate of hot Jupiters from the Kepler data.

Subfields: Astronomy and Astrophysics, Instrumentation

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Citations in the corpus

TESTING IN SITU ASSEMBLY WITH THE KEPLER PLANET CANDIDATE SAMPLE (2013, background): “Santerne et al. (2012) have claimed that the false positive rate for Jupiter-size candidates is higher (∼35”
Trumpeting M dwarfs with CONCH-SHELL: a catalogue of nearby cool host-stars for habitable exoplanets and life (2014, background): “A few hundred of these have been vetted and the overall rate of false positives is generally, but not uniformly, low (Santerne et al. 2012; Colón, Ford & Morehead 2012; Fressin et al. 2013).”
AN EFFICIENT AUTOMATED VALIDATION PROCEDURE FOR EXOPLANET TRANSIT CANDIDATES (2012, background): “Of these, 11 were identified as false positives by Santerne et al. (2012) and one (1187.01) was identified by Colón et al. (2012) to have a color-dependent transit depth.”
TRANSIT TIMING OBSERVATIONS FROM KEPLER. VIII. CATALOG OF TRANSIT TIMING MEASUREMENTS OF THE FIRST TWELVE QUARTERS (2013, background): “01 (Figure 4(b)): This system is probably an eclipsing binary (EB) orbiting a third distant star, causing the light time travel (LITE) effect (Santerne et al. 2012).”
SOPHIE velocimetry of Kepler transit candidates XVII. The physical properties of giant exoplanets within 400 days of period (2015, methodology): “We corrected the RV from the CCD charge transfer inefficiency (Bouchy et al. 2009a) using the calibration described in Santerne et al. (2012b).”
The California-Kepler Survey. I. High-resolution Spectroscopy of 1305 Stars Hosting Kepler Transiting Planets (2017, background): “In contrast, Santerne et al. (2012) found a higher false positive contamination rate among gaint planet candidates of 30% through radial velocity follow-up.”
HOW ROCKY ARE THEY? THE COMPOSITION DISTRIBUTION OF KEPLER’S SUB-NEPTUNE PLANET CANDIDATES WITHIN 0.15 AU (2014, background): “Santerne et al. (2012) qualitatively corroborates this effect via the radial velocity technique by measuring masses of the detected transiting companions, reporting that 35% of the deepest, shortest period PC signals have masses too high for planetary bodies.”
STELLAR ROTATION PERIODS OF THE KEPLER OBJECTS OF INTEREST: A DEARTH OF CLOSE-IN PLANETS AROUND FAST ROTATORS (2013, background): “A literature search and additional tests allowed us to exclude a further 23 targets from our sample: 17 targets were listed as confirmed or likely eclipsing binaries (EB, flag: ‘E’) (Santerne et al. 2012; Cabrera et al. 2012; Muirhead et al. 2013; Mazeh et al. 2013).”
LOW FALSE POSITIVE RATE OF KEPLER CANDIDATES ESTIMATED FROM A COMBINATION OF SPITZER AND FOLLOW-UP OBSERVATIONS (2015, methodology): “The high FPR found in the sample of Santerne et al. (2012) is consistent with the findings of Demory & Seager (2011) for which close-in candidates were also targeted.”
SWEET-Cat: A catalogue of parameters for Stars With ExoplanETs - I. New atmospheric parameters and masses for 48 stars with planets (2013, background): “…of these parameters have already been published in dedicated papers (e.g. Santos et al. 2006; Ammler-von Eiff et al. 2009, – see also Mortier et al. 2013, in prep.) or in planet discovery papers where the spectroscopic analysis was done by our team (see Santerne et al. 2012, for a recent example).”
FALSE POSITIVE PROBABILITIES FOR ALL KEPLER OBJECTS OF INTEREST: 1284 NEWLY VALIDATED PLANETS AND 428 LIKELY FALSE POSITIVES (2016, background): “Also, large candidates typically have high FPPs, in agreement with Santerne et al. (2012) and Santerne et al. (2015).”
PASTIS: Bayesian extrasolar planet validation. I. General framework, models, and performance (2014, background): “This target has a magnitude of 14.3 in the Kepler passband, which is typical for the transiting candidates that can be followed-up spectroscopically from the ground (e.g. Santerne et al. 2012).”
TERRESTRIAL PLANET OCCURRENCE RATES FOR THE KEPLER GK DWARF SAMPLE (2015, background): “The astrophysical false positive contamination rates have observationally (Santerne et al. 2012; Désert et al. 2015) and theoretically (Morton & Johnson 2011; Fressin et al. 2013) been shown to increase towards shorter Porb.”
THE FALSE POSITIVE RATE OF KEPLER AND THE OCCURRENCE OF PLANETS (2013, methodology): “Another estimate of the false positive rate for giant planets was made recently by Santerne et al. (2012), from a subsample of KOIs they followed up spectroscopically.”