K2-140b and K2-180b – Characterization of a hot Jupiter and a mini-Neptune from the K2 mission

J. Korth*, Sz Csizmadia, D. Gandolfi, M. Fridlund, M. Pätzold, T. Hirano, J. Livingston, C. M. Persson, H. J. Deeg, A. B. Justesen, O. Barragán, S. Grziwa, M. Endl, R. Tronsgaard, F. Dai, W. D. Cochran, S. Albrecht, R. Alonso, J. Cabrera, P. W. CauleyF. Cusano, Ph. Eigmüller, A. Erikson, M. Esposito, E. W. Guenther, A. P. Hatzes, D. Hidalgo, M. Kuzuhara, P. Montañes, N. R. Napolitano, N. Narita, P. Niraula, D Nespral, G. Nowak, E. Palle, C. E. Petrillo, S Redfield, J. Prieto-Arranz, H. Rauer, A. M. S. Smith, C. Tortora, V. Van Eylen, J. N. Winn

*Corresponding author for this work

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We report the independent discovery and characterization of two K2 planets: K2-180b, a mini-Neptune-sized planet in an 8.9-d orbit transiting a V = 12.6 mag, metal-poor ([Fe/H]  =  −0.65 ± 0.10) K2V star in K2 campaign 5; K2-140b, a transiting hot Jupiter in a 6.6-d orbit around a V = 12.6 mag G6V ([Fe/H]  = + 0.10 ± 0.10) star in K2 campaign 10. Our results are based on K2 time-series photometry combined with high-spatial resolution imaging and high-precision radial velocity measurements. We present the first mass measurement of K2-180b. K2-180b has a mass of Mp = 11.3 ± 1.9 M and a radius of Rp = 2.2 ± 0.1 R⁠, yielding a mean density of ρp = 5.6 ± 1.9 g cm−3, suggesting a rocky composition. Given its radius, K2-180b is above the region of the so-called ‘planetary radius gap’. K2-180b is in addition not only one of the densest mini-Neptune-sized planets, but also one of the few mini-Neptune-sized planets known to transit a metal-poor star. We also constrain the planetary and orbital parameters of K2-140b and show that, given the currently available Doppler measurements, the eccentricity is consistent with zero, contrary to the results of a previous study.
Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
Pages (from-to)1807-1823
Publication statusPublished - 2019

Bibliographical note

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2019 The author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.


  • Techniques: photometric
  • Techniques: radial velocities
  • Stars: individual: K2-140
  • Stars: individual: K2-180
  • Planets and satellites: fundamental parameters
  • Stars: fundamental parameters

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