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

Cite this

Korth, J., Csizmadia, S., Gandolfi, D., Fridlund, M., Pätzold, M., Hirano, T., Livingston, J., Persson, C. M., Deeg, H. J., Justesen, A. B., Barragán, O., Grziwa, S., Endl, M., Tronsgaard, R., Dai, F., Cochran, W. D., Albrecht, S., Alonso, R., Cabrera, J., ... Winn, J. N. (2019). K2-140b and K2-180b – Characterization of a hot Jupiter and a mini-Neptune from the K2 mission. Monthly Notices of the Royal Astronomical Society, 482(2), 1807-1823. https://doi.org/10.1093/mnras/sty2760