Characterization of Kepler-91b and the Investigation of a Potential Trojan Companion Using EXONEST

Abstract

Presented here is an independent re-analysis of the Kepler light curve of Kepler-91 (KIC 8219268). Using the EXONEST software package, which provides both Bayesian parameter estimation and Bayesian model testing, we were able to re-confirm the planetary nature of Kepler-91b. In addition to the primary and secondary eclipses of Kepler-91b, a third dimming event appears to occur approximately $60^o$ away (in phase) from the secondary eclipse, leading to the hypothesis that a Trojan planet may be located at the L4 or L5 Lagrange points. Here, we present a comprehensive investigation of four possibilities to explain the observed dimming event using all available photometric data from the Kepler Space Telescope, recently obtained radial velocity measurements, and N-body simulations. We find that the photometric model describing Kepler-91b and a Trojan planet is highly favored over the model involving Kepler-91b alone. However, it predicts an unphysically high temperature for the Trojan companion, leading to the conclusion that the extra dimming event is likely a false-postive.

Accepted at The Astrophysical Journal

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• EXONEST: The Bayesian Exoplanetary Explorer
• Analyzing Exoplanet Phase Curve Information Content: Toward Optimized Observing Strategies
• Simultaneous multicolour optical and near-IR transit photometry of GJ 1214b with SOFIA
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• Special cases : moons, rings, comets, trojans