Fine-resolution analysis of exoplanetary distributions by wavelets: hints of an overshooting iceline accumulation

Abstract

We investigate 1D exoplanetary distributions using a novel analysis algorithm based on the continuous wavelet transform. The analysis pipeline includes an estimation of the wavelet transform of the probability density function (p.d.f.) without pre-binning, use of optimized wavelets, a rigorous significance testing of the patterns revealed in the p.d.f., and an optimized minimum-noise reconstruction of the p.d.f. via matching pursuit iterations. In the distribution of orbital periods, $P$, our analysis revealed a narrow subfamily of exoplanets within the broad family of "warm jupiters", or massive giants with $P\gtrsim 300$~d, which are often deemed to be related with the iceline accumulation in a protoplanetary disk. We detected a p.d.f. pattern that represents an upturn followed by an overshooting peak spanning $P\sim 300-600$~d, right beyond the "period valley". It is separated from the other planets by p.d.f. concavities from both sides. It has at least two-sigma significance. In the distribution of planet radii, $R$, and using the California Kepler Survey sample properly cleaned, we confirm the hints of a bimodality with two peaks about $R=1.3 R_\oplus$ and $R=2.4 R_\oplus$, and the "evaporation valley" between them. However, we obtain just a modest significance for this pattern, two-sigma only at the best. Besides, our follow-up application of the Hartigan & Hartigan dip test for unimodality returns $3$ per cent false alarm probability (merely $2.2$-sigma significance), contrary to $0.14$ per cent (or $3.2$-sigma), as claimed by Fulton et al. (2017).