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

TL;DR

This study applies a novel wavelet-based analysis to exoplanet distributions, revealing a potential overshooting accumulation near the iceline and confirming bimodality in planet radii with modest significance.

Contribution

It introduces an innovative wavelet analysis pipeline for exoplanet data, providing new insights into orbital period patterns and planet radius distributions.

Findings

Detected a significant upturn and overshooting peak in the orbital period distribution.

Confirmed bimodality in planet radii with modest statistical significance.

Challenged previous claims of high-significance bimodality using the dip test.

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).