Polar stellar-spots and grazing planetary transits: possible explanation for the low number of discovered grazing planets

TL;DR

This paper proposes that dark polar spots on host stars can obscure grazing planetary transits, explaining why fewer such planets are observed than expected, supported by simulations and observationally consistent properties.

Contribution

It introduces a novel explanation involving dark polar spots causing grazing transits to vanish, supported by simulations and property evaluations.

Findings

Simulations predict more detectable grazing planets than observed.

Dark polar spots can hide grazing transits in light curves.

Polar spot properties align with observational data.

Abstract

We assess a physically feasible explanation for the low number of discovered (near-)grazing planetary transits through all ground and space based transit surveys. We performed simulations to generate the synthetic distribution of detectable planets based on their impact parameter, and found that a larger number of (near-)grazing planets should have been detected than have been detected. Our explanation for the insufficient number of (near-)grazing planets is based on a simple assumption that a large number of (near-)grazing planets transit host stars which harbor dark giant polar spot, and thus the transit light-curve vanishes due to the occultation of grazing planet and the polar spot. We conclude by evaluating the properties required of polar spots in order to make disappear the grazing transit light-curve, and we conclude that their properties are compatible with the expected properties from observations.