Kepler Object of Interest Network^★

I. First results combining ground- and space-based observations of Kepler systems with transit timing variations

¹ Stellar Astrophysics Centre, Ny Munkegade 120, 8000 Aarhus, Denmark
² Institut für Astrophysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, 37077 Göttingen, Germany
e-mail: cessen@phys.au.dk
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 Institut d’Astrophysique de Paris, 98 bis Boulevard Arago, 75014 Paris, France
⁶ NASA Astrobiology Institute, Virtual Planetary Laboratory Team, Seattle, Washington, USA
⁷ Instituto de Astronomía, UNAM, Campus Ensenada, Carretera Tijuana-Ensenada km 103, 22860 Ensenada, B.C. México
⁸ Rosseland Centre for Solar Physics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
⁹ Institute of Theoretical Astrophysics, University of Oslo, PO Box 1029 Blindern, 0315 Oslo, Norway
¹⁰ School of Physics and Astronomy, Monash Centre for Astrophysics (MoCA), Monash University, Clayton, Victoria 3800, Australia
¹¹ Instituto de Astrofísica de Canarias, C/ Vía Láctea s/n, 38205 La Laguna, Tenerife, Spain
¹² Universidad de La Laguna, Dept. de Astrofísica, 38206 La Laguna, Tenerife, Spain
¹³ Aix-Marseille Université, CNRS, LAM, Laboratoire d’Astrophysique de Marseille, Marseille, France
¹⁴ Yunnan Observatories, Chinese Academy of Sciences, PO Box 110, Kunming 650216, Yunnan Province, PR China
¹⁵ Institut de Ciéncies de l’Espai (IEEC-CSIC), C/ Can Magrans s/n, Campus UAB, 08193 Bellaterra, Spain
¹⁶ Observatori del Montsec (OAdM), Institut d’Estudis Espacials de Catalunya (IEEC), C/ Gran Capità 2-4, Edif. Nexus, 08034 Barcelona, Spain
¹⁷ School of Geosciences, Raymond and Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel
¹⁸ Astrophysics Research Centre, Queen’s University Belfast, Belfast BT7 1NN, UK
¹⁹ Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, 14482 Potsdam, Germany
²⁰ Hamburg Observatory, Hamburg University, Gojenbergsweg 112, 21029 Hamburg, Germany
²¹ Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing, National Observatory of Athens, Metaxa & Vas. Pavlou St., Penteli, Athens, Greece
²² Dipartimento di Fisica e Scienze della Terra, Universitá degli Studi di Ferrara, via Saragat 1, 44122 Ferrara, Italy
²³ Department of Astronomy & Astrophysics, University of Chicago, Chicago, IL 60637, USA
²⁴ Institute of Theoretical Physics and Astronomy, Vilnius University, Sauletekio 3, 10257 Vilnius, Lithuania
²⁵ Indian Institute of Astrophysics, Koramangala II block, Bangalore 560034, India
²⁶ Instituto de Astronomía, Universidad Católica del Norte, Av. Angamos, 0610 Antofagasta, Chile
²⁷ Central Astronomical Observatory at Pulkovo of Russian Academy of Sciences, Pulkovskoje shosse d. 65, St. Petersburg 196140, Russia
²⁸ Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnij Arkhyz 369167, Russia
²⁹ Kourovka Astronomical Observatory of Ural Federal University, Mira Str. 19, 620002 Yekaterinburg, Russia

Received: 18 December 2017
Accepted: 9 February 2018

Abstract

During its four years of photometric observations, the Kepler space telescope detected thousands of exoplanets and exoplanet candidates. One of Kepler’s greatest heritages has been the confirmation and characterization of hundreds of multi-planet systems via transit timing variations (TTVs). However, there are many interesting candidate systems displaying TTVs on such long timescales that the existing Kepler observations are of insufficient length to confirm and characterize them by means of this technique. To continue with Kepler’s unique work, we have organized the “Kepler Object of Interest Network” (KOINet), a multi-site network formed of several telescopes located throughout America, Europe, and Asia. The goals of KOINet are to complete the TTV curves of systems where Kepler did not cover the interaction timescales well, to dynamically prove that some candidates are true planets (or not), to dynamically measure the masses and bulk densities of some planets, to find evidence for non-transiting planets in some of the systems, to extend Kepler’s baseline adding new data with the main purpose of improving current models of TTVs, and to build a platform that can observe almost anywhere on the northern hemisphere, at almost any time. KOINet has been operational since March 2014. Here we show some promising first results obtained from analyzing seven primary transits of KOI-0410.01, KOI-0525.01, KOI-0760.01, and KOI-0902.01, in addition to the Kepler data acquired during the first and second observing seasons of KOINet. While carefully choosing the targets we set demanding constraints on timing precision (at least 1 min) and photometric precision (as good as one part per thousand) that were achieved by means of our observing strategies and data analysis techniques. For KOI-0410.01, new transit data revealed a turnover of its TTVs. We carried out an in-depth study of the system, which is identified in the NASA Data Validation Report as a false positive. Among others, we investigated a gravitationally bound hierarchical triple star system and a planet–star system. While the simultaneous transit fitting of ground- andspace-based data allowed for a planet solution, we could not fully reject the three-star scenario. New data, already scheduled in the upcoming 2018 observing season, will set tighter constraints on the nature of the system.