Confirming known planetary trends with Kepler

Numerous trends have arisen in particular from the rich Kepler data set, including that exoplanets are more likely to be found around stars with a high metallicity and the presence of a 'gap' in the distribution of planetary radii at 1.9R_{Earth}_. Here we present a new analysis on the Kepler field, using the APOGEE spectroscopic survey to build a metallicity calibration based on Gaia, 2MASS and Stromgren photometry.

This calibration, along with masses and radii derived from a Bayesian isochrone fitting algorithm, is used to test a number of these trends with unbiased, photometrically derived parameters, albeit with a smaller sample size in comparison to recent studies. We recover that planets are more frequently found around higher metallicity stars; over the entire sample, planetary frequencies are 0.88+/-0.12 per cent for [Fe/H]<0 and 1.37+/-0.16 per cent for [Fe/H]>=0 but at two sigma we find that the size of exoplanets influences the strength of this trend.