Exploring Long-period Architectures: Four New Planet Candidates from Kepler with Periods >342 days

Abstract

The Kepler detection pipeline, as well as the transit method, has a bias towards shorter periods, leaving a dearth of detections at longer orbital periods. This relative lack of detections has left an incomplete picture of the architectures of exoplanet systems within the long-period regime. We have built a single transit detection pipeline, utilizing a classification convolutional neural network and the onboard spacecraft diagnostics of the Kepler spacecraft, to detect long-period planets. We apply our pipeline to all currently known planetary systems in the Kepler field hosting at least one planet with an orbital period longer than 6 days. We manually vet all new signals from our pipeline, and identify four new planetary candidates, all of which are in systems where the inner planets exhibit transit timing variations (TTVs). Two of these candidates, Kepler 1752.02 and Kepler 199.03, cause two transit events that are consistent with periods of $777.78_{-0.02}^{+0.01}$ and $505.495_{-0.004}^{+0.004}$ days, and radii of $3.55_{-0.15}^{+0.15}$ and $2.74_{-0.05}^{+0.05}$ $R_{\oplus }$, respectively. Our remaining two candidates, Kepler 1897.02 and Kepler 1811.02, are single transit candidates with radii $4.81_{-0.19}^{+0.20}$ and $3.25_{-0.30}^{+0.28}$ $R_{\oplus }$, respectively. The shortest orbital periods for these candidates, consistent with the Kepler dataset (gaps and coverage), are 342 days for Kepler 1897.02 and 544 days for Kepler 1811.02. The new planetary candidates, on their own, are incapable of reproducing the observed TTV signals in the inner system. Although difficult to schedule, follow-up observations are needed to further constrain the new candidates and potentially discover the planets causing the perturbations.

23 pages, 19 figures, 9 tables, published in AJ

References in corpus (25)

• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The Transiting Exoplanet Survey Satellite
• The K2 Mission: Characterization and Early results
• DHP Framework: Digital Health Passports Using Blockchain -- Use case on international tourism during the COVID-19 pandemic
• EXOFAST: A fast exoplanetary fitting suite in IDL
• A Technique for Extracting Highly Precise Photometry for the Two-Wheeled Kepler Mission
• Growth Model Interpretation of Planet Size Distribution
• Exoplanet population inference and the abundance of Earth analogs from noisy, incomplete catalogs
• Revisited Mass-Radius relations for exoplanets below 120 Earth masses
• Exoplanet Orbital Eccentricities Derived From LAMOST-Kepler Analysis
• exoplanet: Gradient-based probabilistic inference for exoplanet data & other astronomical time series
• The Occurrence of Rocky Habitable Zone Planets Around Solar-Like Stars from Kepler Data
• A Statistical Reconstruction of the Planet Population Around Kepler Solar-Type Stars
• TTVFast: An efficient and accurate code for transit timing inversion problems
• Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey II: Free-Floating Planet Detection Rates
• Predicting the long-term stability of compact multiplanet systems
• Automatic Classification of Kepler Planetary Transit Candidates
• The population of long-period transiting exoplanets
• ExoMiner: A Highly Accurate and Explainable Deep Learning Classifier that Validates 301 New Exoplanets
• Exoplanet Validation with Machine Learning: 50 new validated Kepler planets
• Accounting for Multiplicity in Calculating Eta Earth
• The PLATO field selection process. II. Characterization of LOPS2, the first long-pointing field
• Visual Analysis and Demographics of Kepler Transit Timing Variations
• Power-2 limb-darkening coefficients for the uvby, UBVRIJHK, SDSS ugriz, Gaia, Kepler, and TESS photometric systems
• Identifying Potential Exomoon Signals with Convolutional Neural Networks