Disintegrating Exoplanets: Creating Size Constraints by Statistically Peering Through the Debris

TL;DR

This study introduces a statistical method to better estimate the true size of disintegrating exoplanets by modeling their lightcurve noise distributions, successfully constraining K2-22b's radius but not Kepler-1520b.

Contribution

It presents a novel approach combining Gaussian and Rayleigh noise modeling with Markov Chain Monte Carlo to improve exoplanet size constraints from complex transit data.

Findings

Constrained K2-22b's radius to approximately 15,000 km.

Failed to constrain Kepler-1520b's radius due to observational challenges.

Demonstrated the effectiveness of joint noise modeling in exoplanet characterization.

Abstract

We study two intriguing exoplanets, Kepler-1520b and K2-22b, that are being disintegrated by their host stars, producing dust and debris pulled from their surface into tails that trail and precede the exoplanets in their orbits, making it difficult to discern the true nature of the objects. Our goal is to constrain the radius of the underlying objects, and while previous studies have done this in the past by selecting shallow transit events, we attempt a new statistical approach to model the intrinsic astrophysical and photon noise distributions simultaneously. We assume that the lightcurve flux distribution is distributed as a convolution of a Gaussian photon noise component and a Raleigh astrophysical component. The Raleigh curve has a finite flux maximum, which we fit with a Hamiltonian Markov Chain. With these methods, a more accurate flux maximum may be estimated, producing a better final value for the radius of these exoplanets. To determine statistical significance, we used the python package PyMC3 to find the posterior distribution for our data with Gaussian, Rayleigh, and joint function curves and plotting it against our collected flux. After completing this analysis, we were able to place a constraint on the maximum radius of K2-22b at approximately 15,000km. However, we were unable to constrain the radius of Kepler-1520b due to either transits obscured by forward scattering of dust or a grazing transit.