An Ultra-short Period Rocky Super-Earth with a Secondary Eclipse and a Neptune-like Companion around K2-141

Luca Malavolta, Andrew W. Mayo, Tom Louden, Vinesh M. Rajpaul, Aldo S. Bonomo, Lars A. Buchhave, Laura Kreidberg, Martti H. Kristiansen, Mercedes Lopez-Morales, Annelies Mortier, Andrew Vanderburg, Adrien Coffinet, David Ehrenreich, Christophe Lovis, Francois Bouchy, David Charbonneau, David R. Ciardi, Andrew Collier Cameron, Rosario Cosentino, Ian J.M. CrossfieldMario Damasso, Courtney D. Dressing, Xavier Dumusque, Mark E. Everett, Pedro Figueira, Aldo F.M. Fiorenzano, Erica J. Gonzales, Raphaëlle D. Haywood, Avet Harutyunyan, Lea Hirsch, Steve B. Howell, John Asher Johnson, David W. Latham, Eric Lopez, Michel Mayor, Giusi Micela, Emilio Molinari, Valerio Nascimbeni, Francesco Pepe, David F. Phillips, Giampaolo Piotto, Ken Rice, Dimitar Sasselov, Damien Ségransan, Alessandro Sozzetti, Stéphane Udry, Chris Watson

Research output: Contribution to journalArticlepeer-review

65 Citations (Scopus)


Ultra-short period (USP) planets are a class of low-mass planets with periods shorter than one day. Their origin is still unknown, with photo-evaporation of mini-Neptunes and in situ formation being the most credited hypotheses. Formation scenarios differ radically in the predicted composition of USP planets, and it is therefore extremely important to increase the still limited sample of USP planets with precise and accurate mass and density measurements. We report here the characterization of a USP planet with a period of 0.28 days around K2-141 (EPIC 246393474), and the validation of an outer planet with a period of 7.7 days in a grazing transit configuration. We derived the radii of the planets from the K2 light curve and used high-precision radial velocities gathered with the HARPS-N spectrograph for mass measurements. For K2-141b, we thus inferred a radius of 1.51 ±0.05 R and a mass of 5.08 ±0.41 M, consistent with a rocky composition and lack of a thick atmosphere. K2-141c is likely a Neptune-like planet, although due to the grazing transits and the non-detection in the RV data set, we were not able to put a strong constraint on its density. We also report the detection of secondary eclipses and phase curve variations for K2-141b. The phase variation can be modeled either by a planet with a geometric albedo of 0.30 ±0.06 in the Kepler bandpass, or by thermal emission from the surface of the planet at ∼3000 K. Only follow-up observations at longer wavelengths will allow us to distinguish between these two scenarios.

Original languageEnglish
Article number107
JournalAstronomical Journal
Issue number3
Publication statusPublished - Mar 2018

Bibliographical note

Funding Information:
V.M.R. acknowledges the Royal Astronomical Society for financial support.

Funding Information:
Parts of this work have been supported by NASA under grants No. NNX15AC90G and NNX17AB59G issued through the Exoplanets Research Program.

Funding Information:
Some of the observations in the paper made use of the NN-EXPLORE Exoplanet and Stellar Speckle Imager (NESSI). NESSI was funded by the NASA Exoplanet Exploration Program and the NASA Ames Research Center. NESSI was built at the Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley.

Funding Information:
The research leading to these results received funding from the European Union Seventh Framework Programme (FP7/ 2007-2013) under grant agreement number 313014 (ETAEARTH).

Funding Information:
P.F. acknowledges support by Fundação para a Ciência e a Tecnologia (FCT) through Investigador FCT contract of reference IF/01037/2013/CP1191/CT0001, and POPH/FSE (EC) by FEDER funding through the program “Programa Operacional de Factores de Competitividade—COMPETE.” P.F. further acknowledges support from FCT in the form of an exploratory project of reference IF/01037/2013/CP1191/ CT0001.

Funding Information:
This work has been carried out in the frame of the National Centre for Competence in Research PlanetS supported by the Swiss National Science Foundation (SNSF). D.E., C.L., F.B., D.S., F.P., and S.U. acknowledge the financial support of the SNSF. D.E. acknowledges support from the European Research Council (ERC) under the European Unions Horizon 2020 research and innovation programme (project FOUR ACES; grant agreement No 724427).

Funding Information:
The HARPS-N project was funded by the Prodex Program of the Swiss Space Office (SSO), the Harvard-University Origin of Life Initiative (HUOLI), the Scottish Universities Physics Alliance (SUPA), the University of Geneva, the Smithsonian Astrophysical Observatory (SAO), and the Italian National Astrophysical Institute (INAF), University of St. Andrews, Queen’s University Belfast and University of Edinburgh.

Funding Information:
This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation.

Funding Information:
This work was performed in part under contract with the California Institute of Technology/Jet Propulsion Laboratory funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute.

Publisher Copyright:
© 2018. The American Astronomical Society. All rights reserved.


  • planetary systems
  • planets and satellites: composition
  • planets and satellites: individual (K2-141b, K2-141c)
  • planets and satellites: interiors
  • stars: individual (K2-141)
  • techniques: photometric
  • techniques: radial velocities

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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