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It Takes Two Planets in Resonance to Tango around K2-146

Lam, KWF; Korth, J; Masuda, K; Csizmadia, S; Eigmueller, P; Kari Stefansson, G; Endl, M; ... Van Eylen, V; + view all (2020) It Takes Two Planets in Resonance to Tango around K2-146. The Astronomical Journal , 159 (3) , Article 120. 10.3847/1538-3881/ab66c9. Green open access

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Abstract

K2-146 is a cool, 0.358M dwarf that was found to host a mini-Neptune with a 2.67 day period. The planet exhibited strong transit timing variations (TTVs) of greater than 30 minutes, indicative of the presence of an additional object in the system. Here we report the discovery of the previously undetected outer planet in the system, K2-146 c, using additional photometric data. K2-146 c was found to have a grazing transit geometry and a 3.97 day period. The outer planet was only significantly detected in the latter K2 campaigns presumably because of precession of its orbital plane. The TTVs of K2-146 b and c were measured using observations spanning a baseline of almost 1200 days. We found strong anti-correlation in the TTVs, suggesting the two planets are gravitationally interacting. Our TTV and transit model analyses revealed that K2-146 b has a radius of 2.25 ± 0.10 RÅ and a mass of 5.6 ± 0.7 MÅ, whereas K2-146 c has a radius of - + 2.59 0.39 1.81 RÅ and a mass of 7.1 ± 0.9 MÅ. The inner and outer planets likely have moderate eccentricities of e = 0.14 ± 0.07 and 0.16 ± 0.07, respectively. Long-term numerical integrations of the two-planet orbital solution show that it can be dynamically stable for at least 2 Myr. We show that the resonance angles of the planet pair are librating, which may be an indication that K2-146 b and c are in a 3:2 mean motion resonance. The orbital architecture of the system points to a possible convergent migration origin.

Type: Article
Title: It Takes Two Planets in Resonance to Tango around K2-146
Open access status: An open access version is available from UCL Discovery
DOI: 10.3847/1538-3881/ab66c9
Publisher version: https://doi.org/10.3847/1538-3881/ab66c9
Language: English
Additional information: This version is the version of record. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: Exoplanet astronomy; Transit photometry; Timing variation methods; Mini Neptunes; Exoplanet systems; Photometry; Astrometric exoplanet detection; Transit timing variation method
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Space and Climate Physics
URI: https://discovery.ucl.ac.uk/id/eprint/10094076
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