Kepler Object of Interest Network

III. Kepler-82f: a new non-transiting 21 M_⊕ planet from photodynamical modelling^★

¹ Institut für Astrophysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
e-mail: jfreude@astro.physik.uni-goettingen.de
² Stellar Astrophysics Centre, Aarhus University, Ny Munkegade 120, 8000 Aarhus, Denmark
³ Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, Israel
⁴ Astronomy Department, University of Washington, Seattle, WA 98195, USA
⁵ Virtual Planetary Laboratory, University of Washington, Seattle, WA 98195, USA
⁶ Rosseland Centre for Solar Physics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
⁷ Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
⁸ Amazon Web Services, Seattle, WA 98121, USA
⁹ Aix-Marseille University, CNRS, CNES, LAM, Marseille, France
¹⁰ Universidad de La Laguna, Departamento de Astrofísica, 38206 La Laguna, Tenerife, Spain
¹¹ Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
¹² Astrophysics Research Centre, Queen’s University Belfast, Belfast BT7 1NN, UK
¹³ Institut de Ciències de l’Espai (IEEC-CSIC), C/Can Magrans, s/n, Campus UAB, 08193 Bellaterra, Spain
¹⁴ Institut d’Estudis Espacials de Catalunya (IEEC), Gran Capità, 2-4, Edif. Nexus, 08034 Barcelona, Spain
¹⁵ Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Metaxa & Vas. Pavlou St., Penteli, Athens, Greece

Received: 13 May 2019
Accepted: 20 June 2019

Abstract

Context. The Kepler Object of Interest Network (KOINet) is a multi-site network of telescopes around the globe organised for follow-up observations of transiting planet candidate Kepler objects of interest with large transit timing variations (TTVs). The main goal of KOINet is the completion of their TTV curves as the Kepler telescope stopped observing the original Kepler field in 2013.

Aims. We ensure a comprehensive characterisation of the investigated systems by analysing Kepler data combined with new ground-based transit data using a photodynamical model. This method is applied to the Kepler-82 system leading to its first dynamic analysis.

Methods. In order to provide a coherent description of all observations simultaneously, we combine the numerical integration of the gravitational dynamics of a system over the time span of observations with a transit light curve model. To explore the model parameter space, this photodynamical model is coupled with a Markov chain Monte Carlo algorithm.

Results. The Kepler-82b/c system shows sinusoidal TTVs due to their near 2:1 resonance dynamical interaction. An additional chopping effect in the TTVs of Kepler-82c hints to a further planet near the 3:2 or 3:1 resonance. We photodynamically analysed Kepler long- and short-cadence data and three new transit observations obtained by KOINet between 2014 and 2018. Our result reveals a non-transiting outer planet with a mass of m_f = 20.9 ± 1.0 M_⊕ near the 3:2 resonance to the outermost known planet, Kepler-82c. Furthermore, we determined the densities of planets b and c to the significantly more precise values ρ_b = 0.98_−0.14^+0.10 g cm⁻³ and ρ_c = 0.494_−0.077^+0.066 g cm⁻³.