LARGER PLANET RADII INFERRED FROM STELLAR “FLICKER” BRIGHTNESS VARIATIONS OF BRIGHT PLANET-HOST STARS

By F. Bastien, Keivan G. Stassun, Joshua A. Pepper. 2014

31 citations recorded by the source corpus.

Most extrasolar planets have been detected by their influence on their parent star, typically either gravitationally (the Doppler method) or by the small dip in brightness as the planet blocks a portion of the star (the transit method). Therefore, the accuracy with which we know the masses and radii of extrasolar planets depends directly on how well we know those of the stars, the latter usually determined from the measured stellar surface gravity, log g. Recent work has demonstrated that the short-timescale brightness variations (“flicker”) of stars can be used to measure log g to a high accuracy of ∼0.1–0.2 dex. Here, we use flicker measurements of 289 bright (Kepmag < 13) candidate planet-hosting stars with Teff = 4500–6650 K to re-assess the stellar parameters and determine the resulting impact on derived planet properties. This re-assessment reveals that for the brightest planet-host stars, Malmquist bias contaminates the stellar sample with evolved stars: nearly 50% of the bright planet-host stars are subgiants. As a result, the stellar radii, and hence the radii of the planets orbiting these stars, are on average 20%–30% larger than previous measurements had suggested.

Subfields: Astronomy and Astrophysics, Computational Mechanics, 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): “We provide full samples of our posteriors on the physical parameters for each star.11 Bastien et al. (2014) use the “granulation flicker” in the Kepler light curves to suggest that approximately 50% of planet host stars have evolved off the main sequence onto the subgiant branch, so that both the…”
A Technique for Extracting Highly Precise Photometry for the Two-Wheeled Kepler Mission (2014, background): “Flicker One of the many unanticipated results from Kepler was an observational correlation between short timescale photometric variability in light curves, referred to as “flicker,” and the surface gravity of the star (Bastien et al. 2013, 2014; Kipping et al. 2014).”
EXOPLANET POPULATION INFERENCE AND THE ABUNDANCE OF EARTH ANALOGS FROM NOISY, INCOMPLETE CATALOGS (2014, background): “There is recent evidence that the stellar radii of Kepler targets might, on average, be underestimated (Bastien et al. 2014), introducing another source of noise.”
FALSE POSITIVE PROBABILITIES FOR ALL KEPLER OBJECTS OF INTEREST: 1284 NEWLY VALIDATED PLANETS AND 428 LIKELY FALSE POSITIVES (2016, background): “The need for caution when estimating the radii of KOI host stars has also been emphasized by Bastien et al. (2014), who find from photometric “flicker” measurements that a significant number of FGK KOI hosts may be slightly evolved.”
The GALAH survey: observational overview and Gaia DR1 companion (2016, background): “…the Kepler Input Catalogue have been shown to have uncertainties of up to ∼ 40% for Solar-type stars (e.g., Verner et al. 2011; Everett et al. 2013; Bastien et al. 2014), and similar uncertainties apply for the majority of K2 targets that have been classified in the Ecliptic Plane Input…”
Revised Radii of Kepler Stars and Planets Using Gaia Data Release 2 (2018, methodology): “Everett et al. (2013) used medium resolution spectroscopy to arrive at a similar conclusion for faint Kepler exoplanet host stars, while surface gravities derived from granulation noise (“flicker”) suggested that nearly 50% of all bright exoplanet host stars are subgiants (Bastien et al. 2014).”
PLANETARY CANDIDATES OBSERVED BY KEPLER. VI. PLANET SAMPLE FROM Q1–Q16 (47 MONTHS) (2015, background): “…et al. 2011; Bruntt et al. 2012; Huber et al. 2014), and several studies have found evidence that KIC log g’s are systematically overestimated for solar-type dwarfs (Verner et al. 2011; Everett et al. 2013; Farmer et al. 2013; Bastien et al. 2014), meaning the radii are underestimated.”
Revised Stellar Properties of Kepler Targets for the Q1-17 (DR25) Transit Detection Run (2016, methodology): “Moreover, several studies have shown that the KIC surface gravities appear to be overestimated for solar-type stars, based on comparisons to asteroseismology (Verner et al. 2011), spectroscopy (Everett et al. 2013) and surface gravities derived from stellar granulation (Bastien et al. 2014).”
The California-Kepler Survey. I. High-resolution Spectroscopy of 1305 Stars Hosting Kepler Transiting Planets (2017, background): “Bastien et al. (2014) noted that Flicker-based gravities were systematically higher than those in the KIC, implying that most Kepler planets (which lacked spectroscopicallydetermined gravities) had radii that were underestimated by 20-30%.”