  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, logg. Recent work
has demonstrated that the short-timescale brightness variations ("flicker") of
stars can be used to measure logg to a high accuracy of ~0.1-0.2 dex (Bastien
et al. 2013). 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, an
astrophysical bias exists that 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.
